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Biology Review
BGHSGT Review in BiologyIOLOGY
CONTENT DOMAINS
I. Cells
II. Organisms
III. Genetics
IV. Ecology
V. Evolution
Content Domain I: Cells
Differentiate between prokaryotic and eukaryotic cells
Comprehend the importance of homeostasis
Characteristics of enzymes
Characteristics of the four major biomolecules
Differentiate Between Prokaryotic and Eukaryotic Cells??
Biologists once looked for clues to aging and diseases by studying organs, tissues, and cultures of cells. With the development of the microscope, biologists focused their attention upon smaller elements of living things: the organelles within the cell. With advancements in the microscope, iologists discovered two types of cells: Prokaryotic and Eukaryotic cells.
PROKARYOTES:
Single-celled organisms that lack internal structures surrounded by membranes. They lack a true nucleus.
Examples:
Bacteria
Archaea
EUKARYOTES:
Single- and multicellular organisms that have cells containing internal, membrane-bound structures. They have a true nucleus containing the cell’s  DNA.
Examples: Plants, Animals, Mushrooms, Amoebas


Living vs. Nonliving
All living things, or organisms, share certain characteristics such as:
??Require food for energy to carry out life processes
??Use energy to maintain homeostasis
??Respond to stimuli in their environment
??Reproduce similar offspring, passing genetic information to them
??Made of cells
Cells must have boundaries. Cells have plasma membranes that serve as a boundary between the cell and its external environment. The plasma membrane is flexible and allows the cell to vary its shape if necessary. It controls the movement of materials entering and exiting the cell. The plasma membrane also helps maintain a chemical balance within the cell. An additional boundary outside of the plasma membrane is the cell wall. The cell wall is thicker than the plasma membrane and inflexible. It protects the cell and gives the cell its shape. Plants, fungi, most bacteria, and a few protists have cell walls.

Animal cells do not have cell walls.
For the Biology EOCT, it is important that you understand the differences between prokaryotic and eukaryotic cells, as well as living and nonliving organisms. Questions for this standard might look like this: Some examples of organelles and their functions:
Nucleus: contains DNA, which controls cellular function
Chloroplasts: capture solar energy for photosynthesis
Golgi bodies: modify, sort, ship proteins and lipids
Mitochondria: ATP formation
Ribosomes: synthesis of polypeptide chains
It is very important that you refer to your textbook for a complete list of cell organelles and their specific functions. Questions relating to this standard may ask you to describe their function. They may also ask you to distinguish between plant and animal cells.
1 Unlike prokaryotic cells, eukaryotic cells have the capacity to
A assemble into multicellular organisms
B establish symbiotic relationships with other organisms
C obtain energy from the Sun
D store genetic information in the form of DNA
2 Inside eukaryotic cells are membrane-bound structures called
A cell walls
B cilia
C organelles
D cytoplasm

??The Importance of Homeostasis??
Organisms maintain their internal equilibrium by responding and adjusting to environmental stressors. For example, aquatic organisms must respond to changes in water temperature, sunlight, chemicals, and other organisms. All organisms must adjust and respond to changes in their environment. Failure to do so may result in death. Living cells maintain a balance between materials entering and exiting the cell. Their ability to maintain this balance is called homeostasis. It is important for a cell to control internal concentrations of water, glucose, and other nutrients, while eliminating cellular wastes.
Plasma Membrane
One function of the plasma membrane is to control what comes into and out of a cell. In this way, the plasma membrane helps to maintain the proper concentrations of substances inside the cell. Selective permeability is the property of the membrane that allows certain materials to pass through the cell while keeping others out. It also allows different cells to perform different activities within the same organism. An example of this is the nerve cell. Nerve cells respond to a certain chemical that is present in the bloodstream. Other cells are exposed to this chemical but not affected by it.
Passive / Active Transport
There are various mechanisms that transport materials in and out of the cell. Passive transport is the movement of materials across the plasma membrane without the use of the cell’s energy.
Diffusion: the movement of substances across the plasma membrane from an area of high concentration to an area of lower concentration.
Osmosis: the diffusion of water molecules through a selectively permeable membrane from an area of high concentration to lower water concentration. Facilitated transport: occurs when a carrier molecule embedded in the plasma membrane transports a substance across the membrane by means of diffusion.
Active transport is the movement of materials across cell membranes that requires energy. Active transport is the process by which materials are moved against a concentration gradient, as in the sodium-potassium pump. Also, the movement of large particles into or out of the cell is done by the process of active transport. Endocytosis: a process in which a cell surrounds and takes in material from its environment.  Exocytosis: a process by which materials leave the cell.

Studying the following word parts will help you
determine the meanings of certain words you will
come across on the Biology EOCT.
BIO-“life” LOGY-“study of
ENDO-“inside” CYTO-“cell”
EXO-“outside” OSIS-“process or action”
An example of a question on the Biology EOCT may look like this:
Osmosis is the movement across a membrane due to differential solute concentrations. Excretion of digestive enzymes is triggered by chemical changes in the stomach. White blood cells are released in response to the presence of a pathogen. Calcium is released as a nervous signal is sent to the muscle cells. So, the correct answer is A.
Which of the following examples illustrates osmosis?
A Water leaves the tubules of the kidney in response to the hypertonic fluid surrounding the tubules.
B Digestive enzymes are excreted into the small intestine.
C White blood cells consume pathogens and cell debris at the site of an infection.
D Calcium is pumped inside a muscle cell after the muscle completes its contraction.
??Characteristics of Enzymes??
All cells maintain, increase, and decrease the concentration of substances by developing metabolic pathways. A metabolic pathway is an orderly sequence of reactions with specific enzymes that act at each step along the way. Enzymes are catalytic molecules. That is, they speed up specific reactions without being used up in the reaction. Enzymes are proteins.
Enzymes have four special features in common:
1. They do not make processes happen that would not take place on their own. They just make the processes take place faster!
2. Enzymes are not permanently altered or used up in reactions.
3. The same enzyme works for the forward and reverse directions of a reaction.
4. Each enzyme is highly selective about its substrate.
Substrates are molecules which a specific enzyme can chemically recognize and to which it can bind. Substrates undergo chemical changes to form new substances called products. Each substrate fits into an area of the enzyme called the active site. It is like a lock-and-key mechanism. Once the enzyme-substrate complex is together, the enzyme holds the substrate in a position where the reaction can occur. Once the reaction is complete, the enzyme unlocks the product and the enzyme is free to facilitate another reaction.
CRITICAL THINKING
The rate of a reaction depends in part on the concentration of the enzyme. If the enzyme is diluted, its concentration is
lowered, which slows the reaction rate. Once substrates have reached the transition state, they react spontaneously. Substrate molecules must collide with a minimum amount of energy to reach the transition state. This amount of energy is called the activation energy. It is like traveling over a hill. The lower the hill, the less energy it takes to get to the top, and the faster you go over it. The higher the hill, the more energy it takes to get to the top, and the longer it will take you to go over it.
???It takes less energy to boost reactants to the transition state of a lower energy hill. The reaction will proceed more rapidly. Enzymes are critical to life processes. Carbonic anhydrase is an enzyme that speeds up the process by which carbon dioxide leaves cells and enters the bloodstream so it can be removed from the body. The enzyme lipase is produced by the pancreas and functions in the digestion of lipids. RNA polymerase is an enzyme that facilitates the process of
transcription. Some diseases, such as Tay-Sachs and phenylketonuria, occur when the body fails to make a critical enzyme.
A question on the Biology EOCT may
look like this: Food is commonly refrigerated at temperatures 2° C to 7° C to slow the rate of spoilage by bacteria. Which of the following best explains why refrigeration at these temperatures slows the spoilage of food?
A Bacteria that cause food spoilage are killed by these low temperatures.
B Bacteria that cause food spoilage multiply rapidly at these temperatures.
C The enzymes in bacteria that cause food spoilage are not active at these temperatures.
D The enzymes in bacteria that cause food spoilage are denatured at these temperatures.

The correct answer is C. The enzyme activity of food spoilage bacteria is greatly reduced at typical food refrigeration temperatures. The rate of reproduction of food spoilage bacteria is decreased, not increased, at low temperatures. Typical refrigeration temperatures are not low enough to kill bacteria. Enzymes, which are proteins, are denatured by high, not low temperatures.

??The Four Major Biomolecules??
Carbohydrates, lipids, proteins, and nucleic acids are the foundations for the structure and function of every living cell in every organism. They are the building materials of the body and the storehouse for energy for every activity.
Carbohydrates:
A carbohydrate is a simple sugar or a molecule composed of two or more simple sugars. In general, the ratio of carbon, hydrogen, and oxygen atoms is 1:2:1 in a carbohydrate molecule. There are three classes of carbohydrates: monosaccharides, oligosaccharides, and polysaccharides. Glucose, sucrose, starch, and cellulose are examples of carbohydrates. “Saccharide” means sugar. “Mono” means one. Put the two together: one sugar unit. An oligosaccharide is a short chain of two or more covalently bonded sugar units. “Poly” means many. A polysaccharide is a straight or branched chain of sugar units, where you may have hundreds or thousands of the same or different kinds of sugars bonded to one another.
Lipids:
Lipids are organic compounds that have more carbon-hydrogen (C-H) bonds and fewer oxygen atoms than carbohydrates. They are extremely important for the proper functioning of organisms. Lipids are commonly called fats and oils. They are insoluble in water due to the nonpolarity of the molecules. Cells use lipids for long-term energy storage, insulation and protective coatings. Lipids are the major component of the membranes surrounding all living organisms. Waxes are long-chain fatty acids attached to an alcohol. An example is cutin in plants. It helps the plants retain water.
Proteins:
Proteins belong to the most diverse group. They are large, complex polymers essential to all life. They are composed of amino acids made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Proteins are important in muscle  contraction, transporting oxygen in the blood, and the immune system. Proteins, like lipids, are an important component of
the membranes that surround cells. Collagen, enzymes, hemoglobin, insulin and antibodies are examples of proteins.
Nucleic Acids:
Nucleic acids are complex macromolecules that store information in cells in the form of a code. To form nucleic acids, four different kinds of nucleotides are strung together. A nucleotide is a small organic compound that consists of a five-carbon sugar, a nitrogen. containing base, and a phosphate group. Nucleotides are the structural units of adenosine phosphates, nucleotide coenzymes, and nucleic acids. They make up ATP, NAD+,
NADP+, DNA, and RNA.

Sample Questions for Content Domain I: Cells
This section has some sample questions for you to try. After you have answered all of the questions, check your answers in the “Answers to the Content Domain I Sample Questions” section that follows. This section will give you the correct answer to each question, and it will explain why the other answer choices are incorrect.
1 The assembly of proteins in a cell takes place in the
A nucleus
B vacuoles
C cytoplasm
D mitochondria
2 Which of the following is an organism whose cell(s) lack(s)
membrane-bound organelles?
A nucleolus
B chromatin
C eukaryote
D prokaryote
3 In all reptiles, birds, and mammals, the processes of
excretion, water and salt balance, and the regulation of pH in body fluids are controlled by the kidneys. This is an example of the organism maintaining
A reabsorption
B homeostasis
C insulation
D hibernation
4 Proteins are long chains or polymers made up of
A nucleotides
B carbohydrates
C amino acids
D lipids
5 Which of the following molecules provides the greatest amount of energy per gram of mass when metabolized?
A carbohydrate
B nucleic acid
C protein
D lipid
6 Which of the following environmental changes can cause
an increase in the rates of reactions in cells?
A increased temperature
B decreased enzyme concentrations
C increase activation energy requirement
D decreased diffusion rates
Answers
1. Answer: C Standard: SB1.a; Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction.
The nucleus is the location of the cell’s DNA, which contains the code for producing proteins. Vacuoles store various substances in the cell. Mitochondria are organelles that convert energy to forms useful to the cell. The synthesis of proteins takes place on ribosomes, which are located in the cytoplasm of the cell.
2. Answer: D Standard: SB1.a; Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction.
A prokaryotic cell is the one that lacks membrane-bound organelles. Therefore D has to be the correct answer. Answers A and B are both found within eukaryotic cells.
3. Answer: B Standard: SB1.a; Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction.
Answers A, C, and D are processes that occur as a result of organisms maintaining homeostasis. B is the correct answer because that is the main process by which the others can occur.
4. Answer: C Standard: SB1.c; Identify the function of the four major macromolecules (i.e., carbohydrates, proteins, lipids, nucleic acids). Nucleotides are molecules made of phosphate groups, sugar, and a nitrogenous base. Carbohydrate molecules are composed of carbon, hydrogen, and oxygen. Lipids are composed of carbon, hydrogen, and oxygen and contain fewer oxygen atoms than carbohydrates. Amino acids are the building blocks of proteins.
5. Answer: D Standard: SB1.c; Identify the function of the four major macromolecules (i.e., carbohydrates, proteins, lipids, nucleic acids).
The correct answer is D. Lipid molecules store about 9 kilocalories of energy per gram because of the number of double bonds between the carbon and oxygen atoms. The other macromolecules do not contain as many high-energy bonds per gram so do not provide as much energy.
6. Answer: A Standard: SB1.b; Explain how enzymes function as catalysts .
The correct answer is A. The enzymes in organisms must be at the appropriate temperature to function. Enzymes will work more rapidly as temperatures increase, until they reach temperatures at which they become denatured. If enzyme concentrations are decreased, there are fewer available enzyme molecules to combine with substrate molecules and the rate of reaction will decrease. Each substrate molecule
will have to wait for an enzyme molecule to be freed up after catalyzing a reaction.  Increasing the activation energy will slow the reaction because more energy will be required for the reaction to take place. Decreasing the rate of diffusion of water into and out of the cell would have little effect on the rate of reaction catalyzed by enzymes.
Content Domain II: Organisms
Spotlight on the Standards
??Energy Is Needed by all Organisms to Carry Out Processes??
Energy in a Cell
All life on Earth depends on the flow of energy. The number one source of this energy is the Sun. Plants and other photosynthetic organisms are the entry point for this flow of energy. The process of photosynthesis supports almost all life on Earth directly or indirectly. Carbohydrates are a temporary depository of this transferred solar energy,
ready to be used by the cells of these photosynthetic organisms or by the cells of organisms, such as animals, fungi, or microbes that consume plant materials. Energy from the sun is stored in nutrient molecules and then released by the metabolism of living cells. In all cells, the processes of life are constantly moving and rearranging atoms, ions, and molecules. All this biological work requires energy.



Understanding ATP
ATP, adenosine triphosphate, is a special molecule that stores and releases the energy in its bonds when the cell needs it. Cells work constantly to maintain a vast supply of this energy storage molecule. The energy stored is released when ATP is split into ADP, adenosine diphosphate, plus an inorganic phosphate. Remember that ATP and ADP are nucleotides, which are the building blocks of nucleic acids. When the appropriate enzyme is present, the terminal phosphate group of an ATP molecule can be transferred to a variety of other compounds. This process is known as phosphorylation.

This section will focus on understanding of the relationship between single-cell and multicellular organisms and the increasing complexity of systems.  The EOCT questions will also measure your ability to trace the development of the classification of organisms according to the six kingdom model. This domain is based on the following
standards:
??Energy is needed by all organisms to carry out processes
??Understanding the binomial nomenclature system and its
Basis
The energy released when ATP is split is stored in other energy-intermediate molecules and used to power other biological processes. Most of these processes are endergonic biological reactions in cells.
An endergonic reaction is any chemical reaction in which the products have more total energy and more free energy than did the reactants. Endergonic reactions require the input of energy from another source before they can take place.
Consider the following reaction:
ATP ? ADP + P + energy
By removing a phosphate group, energy is released for chemical reactions to occur in the cell and ATP becomes ADP. When the cell has an excess of energy, the energy is stored in the bond when the phosphate group is added to the ADP. The double arrow indicates that the reaction occurs in both directions. ATP seems to have become the major energy link between energy-using and energy-releasing reactions. The amount of free energy released when it breaks down is suitable for use in most cellular reactions.

Examples of ways that cells use energy
Cells use energy to make new molecules, including enzymes, and to build cell organelles and membranes. Cells also use energy to maintain homeostasis. Some cells, such as muscle cells, use energy from ATP in order to move. Nerve cells are able to transmit impulses by using ATP to power the active transport of certain ions. Lightning bugs, certain caterpillars, and many deep-sea organisms produce light from a process known as bioluminescence. The light that is produced is a result of a chemical reaction that is powered by the breakdown of ATP.  

An example of a question on the Biology EOCT may look like this:
Compared to unicellular organisms, cells of multicellular organisms have
A fewer functions
B thicker membranes
C larger nuclei
D less variation
The correct answer is A. Unicellular organisms are self contained. All functions are performed in the one cell. Multicellular organisms have use of specialized and differentiated cells, which perform specific functions. The more complex the organism, the more specialized the cells. Cells of multicellular organisms do not have thicker cell
membranes or larger nuclei than unicellular organisms. Multicellular organisms have greater variation between them by nature of their specialization.
Trapping Energy - Photosynthesis
Many of the carbon atoms and oxygen molecules that you breathe once cycled through the tissues of a plant. Plants, algae, and other photosynthetic organisms are important to the maintenance and balance of life on Earth. They convert solar energy to chemical energy in the form of carbohydrates. These organisms must also break down carbohydrates to form ATP. These carbohydrates are usually in the form of simple sugars, mainly glucose.
Autotrophs trap energy from the sun and use this energy to build carbohydrates in a process known as photosynthesis. This trapped energy is used to convert the inorganic raw materials CO2 and H2O to carbohydrates and O2. The key to this process is the pigment chlorophyll.
The general equation for photosynthesis is as follows:
6CO2 + 6H2O + energy from sunlight ? C6H12O6 + 6O2

The Light Reaction in Summary
Light reactions take place in the chloroplasts. A lipid bilayer membrane surrounds the chloroplast. Inside the chloroplast is a gel like matrix called the stroma, which contains the ribosomes, DNA, and material for carbohydrate synthesis. The most prominent structures in the chloroplasts are stacks of flattened sacs called grana. Each of these grana contains thylakoids,which are interconnected to each other. It is in the thylakoids that the light reaction takes place. Light hitting chlorophyll causes electrons in the chlorophyll to gain energy and leave the chlorophyll molecule. As these electrons pass down the electron transport chain, they lose energy. This energy is used to make ATP. Water breaks up into hydrogen and oxygen and electrons from water replace the electrons lost by the chlorophyll. Electrons, along with hydrogen ions from water, are added to NADP+ to produce NADPH, which carries the energy to the Calvin cycle.
Two Main Reactions of Photosynthesis:
1. Light reactions—These reactions split water molecules, providing hydrogen and an energy source for the Calvin cycle. Oxygen is given off.
2. Calvin cycle—the series of reactions that form simple sugars using carbon dioxide and hydrogen from water.
The light reaction is the photo part of photosynthesis.
The Calvin cycle is the synthesis part of photosynthesis.

The Calvin Cycle in Summary
The Calvin cycle reaction takes place in the stroma of the chloroplasts. Carbon dioxide combines with hydrogen to form simple sugars that are used to make other carbohydrates such as complex sugars, starches, and cellulose. An enzyme adds the carbon atom of carbon dioxide to a 5-carbon molecule. The carbon is now fixed in place in an organic molecule. This process is known as carbon fixation. When the carbon combines with the 5-carbon molecule, a 6-carbon molecule forms and immediately splits into two 3-carbon molecules. The two 3-carbon molecules formed are called PGA molecules
(phosphoglyceric acid). These molecules are converted into two 3-carbon sugars, PGAL, using the hydrogens of NADPH + H+ and energy from ATP. Some of these sugars leave the cycle and are used to form other complex carbohydrates.


Cellular Respiration and ATP Cycle
Once plants use light energy to form carbohydrates, other organisms, called consumers, can then use this carbohydrate energy for their own life processes. One way carbohydrate energy is used by organisms is through the process of cellular respiration. This is a multi-step operation. First, glucose is carried to the cell by the bloodstream. In the cytoplasm, the glucose is formed into pyruvic acid by the process of glycolysis. This process uses 2 molecules of ATP, but produces 4 molecules of ATP. The pyruvic acid moves into the mitochondria, where it is broken down into CO and a 2-carbon acetyl group. This acetyl group binds to coenzyme A and then enters the Krebs cycle. In the Krebs cycle, further reactions take place that release CO and high-energy electrons. These electrons are accepted  by NAD+ and FAD+, forming NADH and FADH. NADH and FADH then move to the inner membrane of the mitochondrion where they pass through the electron transport chain.
Here, electrons are gradually released, producing a total of 32 ATP molecules. The NAD+ and FAD+ then return to the Krebs cycle and repeat the process.

Krebs Cycle Electron Transport Chain
The ATP produced in the process of cellular respiration then provides energy for other cellular processes. To release this energy, ATP loses a phosphate group , becoming ADP. This ADP can then gain a phosphate group during cellular respiration to once again store energy as ATP.

ATP Cycle
The Biology EOCT will assess your knowledge and  understanding of the process of photosynthesis, the ATP-ADP cycle, and the importance of energy to all life. A question on the test may look like this:
The complexity of body systems differs greatly among organisms. Which of the following organisms has developed organ systems for obtaining and utilizing energy?
A bacterium
B mushroom
C mouse
D virus
The correct answer is C. The mouse has complex body systems formed from specialized cells that form tissues that are organized into organs, such as the stomach, pancreas, small intestine, and liver. These organs work together in organ systems to perform specific roles that support life. Bacteria are single-cell organisms that do not have tissues or organ systems. Viruses do not exist as cells. The mushroom is multicellular, but does not have tissues organized into organs.

The Binomial Nomenclature System
Have you ever been to a zoo and been overwhelmed by the number of different species of animals you saw? Or have you taken a walk in a forest and been amazed by the different plants that you see on the forest floor? What you have seen is a small fraction of what is actually inhabiting our planet with us. In an attempt to make sense of the diversity of life, one tool that scientists use is the classification system.
Classification is the grouping of objects based on similarities. Aristotle, who lived from 384 to 322 BC, was the first to use the classification system. He classified living things into two categories: plants and animals. Plants were classified as shrubs, herbs, or trees. Animals were classified according to where they lived. It wasn’t until the 18th century that Carolus Linnaeus, a Swedish botanist, developed a system that is still used today. Linnaeus based his classification on characteristics of organisms that were similar. Take bats, for example. Even though bats fly, Linnaeus grouped bats with mammals because they share similar characteristics; they have hair and produce milk to feed their young. Linnaeus also developed the two word system used to identify species: binomial nomenclature. The first word identifies the genus and is always capitalized. The second word, species, is a descriptive word of that genus and is never capitalized. An example of this would be the following:

Quercus alba: is the name for the white oak (alba is Latin for “white”) Quercus rubra: is the name for the red oak (rubra is Latin for “red”)

Taxonomy is the branch of biology dealing with the grouping and naming of organisms. The person who studies taxonomy is called a taxonomist. There is a vast array of organisms that we know of, but taxonomists are still identifying organisms. They compare the internal and external structures, analyze the chemical makeup, and compare the evolutionary relationships of species. The taxonomist has a tremendous job. The number of species identified by taxonomists is growing at different rates among different groups of organisms. With the advancing technology of the microscope, many more microorganisms have been discovered. Scientists are also exploring tropical forest canopies and deep ocean areas where they are discovering new species. Knowledge of relationships among species helps the taxonomist identify and group these “new” species into the right class. A question on the Biology EOCT may look like this:
One main difference between members of the Kingdoms Plantae and Animalia is
the ability to
A obtain energy
B reproduce
C move
D exchange gases
The correct answer is C. Members of the Kingdom Plantae can grow and bend toward light, but they cannot move their structural parts. Both plants and animals obtain energy and reproduce to maintain life and both exchange gases in the process of respiration. Plants also take in carbon dioxide in the process of photosynthesis.

The Six Kingdoms
The number of kingdoms in early classification systems varied greatly. In Aristotle’s time, scientists had not yet studied geological time frames. Phylogenetic relationships were not a part of classifying organisms. These early classification systems were based on structural differences that were seen. As scientists discovered evolutionary relationships among species, the classification system changed or was modified to fit these new discoveries. From Aristotle’s two divisions, plants and animals, we now have the six kingdom system.
The six kingdoms are comprised of the following:
Kingdoms Eubacteria (true bacteria) and Archaebacteria contain prokaryotes, cells without membrane-bound organelles. Prokaryotes are microscopic, and most are unicellular. The Archaebacteria are mainly found in extreme environments like the deep oceans, hot springs, and swamps. Protists are unicellular and multicellular organisms with a variety of characteristics. Protists are eukaryotic organisms that lack complex organ systems and live in moist environments.
Fungi are consumers that stay put. They are unicellular or
multicellular heterotrophic eukaryotes that absorb nutrients from dead and decaying matter by decomposing dead organisms and wastes in the environment. Plants are multicellular eukaryotes that photosynthesize. Most have cellulose cell walls and tissues that have been organized into organs and organ systems. Animals are multicellular consumers. Animal cells do not have cell walls. Their tissues have been organized into complex organ systems; the nervous system, muscle system and digestive system, as well as others. The organisms are grouped into kingdoms based on
genetic and anatomic similarities. At the phylum level, organisms are subdivided again based on evolutionary traits. Organisms are further divided into different classes based upon shared physical characteristics. Within each class, organisms are grouped into orders based on a more specific and limited set of characteristics. This subdividing and grouping has 7 levels in the modern classification system. The most specific level is Species. Members of a species are considered to be the same “kind” of animal and can reproduce with other members of the same species.

Levels of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Eubacteria
Archaebacteria
Protists
Fungi
Plants
Animals
Below is an example of classification. This is the classification of the largemouth bass, the official state fish of Georgia.
Kingdom Animalia (multicellular organisms that eat food)
Phylum Chordata (animals with a backbone)
Class Actinopterygii (ray-finned fishes)
Order Perciformes (perch-like fishes)
Family Centrarchida (sunfishes)
Genus Micropterus (types of bass)
Species salmoides (largemouth bass)
Sample Questions for Content Domain II: Organisms
This section has some sample questions for you to try. After you have answered all of the questions, check your answers in the “Answers to the Content Domain II Sample Questions” section that follows. This section will give you the correct answer to each question, and it will explain why the other answer choices are incorrect.
1 The function of chlorophyll in a light reaction is to
A bind CO2 to H2O
B split to produce O2
C trap light energy
D act as a source of CO2
2 A group of prokaryotes that live in
extreme environments are the
A viruses
B protists
C eubacteria
D archaebacteria
3. Which of the following best illustrates why the modern
Linnaean classification system has replaced the system developed by Aristotle?

A Flying insects fly over both land and water.
B Eating habits of reptiles and some land mammals are
different.
C Sea snake bones are similar to those of reptiles that live on land.
D Birds are warm-blooded like mammals.
4 Scientists have discovered a new species of animal. Which would provide the best basis for classifying this new species?
A DNA comparison
B diet of animal
C habitat of animal
D appearance of animal

Answers
1. Answer: C Standard SB3.a; Relate the complexity and organization of organisms to their ability for obtaining, transforming, transporting , releasing, and eliminating the
matter and energy used to sustain the organism.
Light reactions are the first step in the process of photosynthesis. It is the job of the chlorophyll to trap this light energy. So C is the correct answer. Remember, light
reactions do not involve CO2 and no sugars are produced, making the other answers incorrect.
2. Answer: D Standard SB3.b; Examine the evolutionary basis of modern classification systems. (six kingdoms)
Archaebacteria is the correct answer. Eubacteria are considered the true bacteria, such as streptococcus, and cyanobacteria. Protists are eukaryotes and live in moist environments. Viruses are genetic entities that can reproduce only in living cells.
3. Answer: C Standard SB3.b; Examine the evolutionary basis of modern classification systems. (six kingdoms)
The correct answer is C. The modern classification systems employ the use of homologous structures to determine evolutionary relationships. Habitat location and eating habits are not accurate indicators of relationships because animals have evolved to be successful in different environments, but may still have common ancestors. Birds are warm-blooded, but are more closely related to reptiles than to mammals.
4. Answer: A Standard SB3.b; Examine the evolutionary basis of modern classification systems. (six kingdoms)
The correct answer is A. DNA contains the genetic information that results in organisms having specific proteins that are arranged to form cells and body systems. Organisms
with similar DNA have a common ancestor. Diet and  appearance are more a result of adaptations to habitat.
Content Domain III: Genetics
Spotlight on the Standards
??Distinguish between DNA and RNA??
?? Explain the role of DNA in storing and
transmitting cellular information??
Our bodies contain millions of cells that are considered storehouses as well. Just as each book in a library contains information, cells also are encoded with information that is needed to produce a trait. When an acorn falls from an oak tree, the acorn will grow into another oak tree, not a maple tree or pine tree. For thousands of years, people have wondered how sons and daughters have certain characteristics like their parents. How does this happen? Where does it all take place? The phrase “like begets like” becomes very clear when we study genetics. Genetics is the branch of biology that studies heredity, the passing on of characteristics
from parents to offspring. These characteristics are called traits. Genetics will focus on your ability to understand how biological traits are passed on to successive generations. Your knowledge will be tested according to the following standards:
??Distinguish between DNA and RNA
??Explain the role of DNA in storing and transmitting cellular
information
??Using Mendel’s laws, explain the role of meiosis in reproductive variability
??Describe the relationships between changes in DNA and
appearance of new traits
??Compare advantages of sexual and asexual reproduction in
different situations
??Examine the use of DNA technology in forensics, medicine, and agriculture
DNA
You have learned that DNA is an example of a complex biological polymer called a nucleic acid. Remember that nucleic acids are made up of smaller subunits called nucleotides. The components of a DNA nucleotide are deoxyribose, a phosphate group, and a nitrogen base. These nitrogen bases are in the shape of a ring that contains one or more atoms of nitrogen. In DNA, there are four possible nitrogen bases – adenine (A),
guanine (G), cytosine (C), and thymine (T). Let’s take a closer look at the structure of DNA. In DNA, nucleotides combine to form two long chains that intertwine with each other, like a ladder that has twisted into a spiral. Another name for this spiral is the double helix (double because there are two strands). The two strands of nucleotides are held together by weak hydrogen bonds between the nitrogen-containing bases. The sides of the ladder consist of phosphate groups alternating with a five-carbon sugar. In DNA, deoxyribose is the 5-carbon sugar. The hydrogen bonding allows for only certain base pairings. In DNA, adenine will bond with thymine, and guanine will bond with cytosine (A-T and G-C).
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The sequence of nucleotides forms the unique genetic information of an organism. How can organisms be so different if their genetic material is made of the same molecules? A squirrel is different from a cat that is different from a dog because the order of nucleotides in their DNA are different. DNA has the unique ability to make an exact copy of itself in a process called replication. During DNA replication, an enzyme breaks the hydrogen bonds between
nitrogen bases that hold the two strands together. This enzyme “unzips” the DNA molecule, allowing free nucleotides in the nucleus to bond to the new single strands by
base-pairing. This process will continue until the entire molecule has been unzipped and replicated. Each new strand formed is a complement of one of the original, or parent,
strands. That means it matches the original strand. When all the DNA in the chromosomes of the cell have been copied by replication, there are now two copies of the genetic information that will be passed on to new cells during mitosis or to new generations through the process of meiosis. A test question on the Biology EOCT may look like this:
Which of the following shows how information is transformed to make a protein?
A DNA RNA protein ? ?
B gene chromosome protein ? ?
C cell respiration ATP protein ? ?
D ATP amino acid protein ? ?

The correct answer is A. DNA contains the genetic information for producing proteins. RNA copies this information, collects the needed amino acids and carries them to the ribosomes, where they are assembled into proteins. Genes are located on strands of DNA and contain information for specific traits. Chromosomes are composed of DNA
molecules and proteins. Cell respiration is a process by which energy is transformed so it can be used for cell activities. ATP is an energy-storage molecule that is used in some
forms of cell respiration. Amino acids are the molecules used to construct proteins. Remember that DNA is found inside the cell’s nucleus, coiled into chromosomes.
RNA
RNA molecules, like DNA, are made of nucleotides. The difference is that in RNA nucleotides, the sugar is ribose and the nitrogen-containing base uracil replaces thymine.
Uracil is paired with adenine. RNA is a single strand of nucleotides. Scientists have discovered that it is the RNA that moves the information from DNA in the nucleus to the
ribosomes in the cytoplasm in a process known as transcription.
Transcription is similar to the DNA process of replication, but only one strand of nucleotides is formed. It is the job of mRNA (messenger RNA) to carry the message of
the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized. Some portions of the DNA “code” for the RNA that makes up
ribosomes. This type of RNA is called rRNA, (ribosomal RNA). Scientists have recently discovered that it is this rRNA that helps to produce enzymes needed to bond amino acids together during protein synthesis.
Translation is the process of converting the information in a sequence of nitrogen bases in mRNA into a sequence of amino acids that make up proteins. If proteins are to be
formed, the amino acids located in the cytoplasm must be brought to the ribosomes. This is accomplished by tRNA (transfer RNA). Transfer RNA brings the amino acids to the
ribosomes so protein synthesis can take place. To have the correct translation of the code, mRNA codons must join with the correct anticodon of the tRNA. A codon is a group of
3 nitrogenous bases on an mRNA molecule that carries the code for a specific amino acid. An anticodon is a set of 3 nitrogenous bases on a tRNA molecule that matches a
codon on an mRNA molecule.

Transference:
Transference is when tRNA brings amino acids to the ribosomes, so they can be assembled into proteins.
In summary:
Messenger RNA (mRNA) carries the message of the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm. At the ribosomes, the mRNA sequence is
translated into a protein in a process known as translation. Transfer RNA (tRNA) transfers the amino acids in the cytoplasm to the ribosomes. The amino acids are lined up
in the coded sequence to form a specific protein.
Information on mRNA is used to make a sequence of amino acids into a protein by which of the following processes?
A replication
B translation
C transcription
D transference

??Using Mendel’s laws, explain the role of meiosis in reproductive variability ??
??Describe the relationships between changes in DNA and appearance of new traits?? Gregor Mendel, an Austrian monk, was the first to succeed in predicting how traits are
carried from one generation to the next. He used pea plants in his experiments because they reproduce sexually. He was very careful to study one trait at a time to control the
variables. He would manipulate flower parts in order to fertilize the female gamete with the male gamete in the desired parent plants. Mendel discovered that when he crossed tall plants with short plants, the first generation of offspring (F1) were all tall. When he let the
F1 plants self-pollinate, Mendel found that three-fourths of their offspring (F2) were tall and one-fourth of the F2 plants were short. The short trait had reappeared in the second
generation (F2). Mendel came to the conclusion that each organism has two factors for each of its traits. Mendel called the trait that appeared in the first generation dominant
and the trait that seemed to disappear recessive. Today, scientists call these factors genes. Genes are located on the chromosomes and can exist in alternative forms called alleles.
Alleles are found on different copies of chromosomes, one from the female and the other from the male. If the two alleles in a pair are identical, then the trait is called homozygous. If the two alleles are different, then the trait is called heterozygous. Genetic crosses that involve one trait are called monohybrid crosses, while dihybrid crosses involve two traits. Outcomes of genetic crosses can be predicted by using the laws of probability. Using a Punnett square will give the possible results of genetic crosses.

Consider the following genetic cross and its corresponding Punnett square:
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Genetic terms
? Allele
? Dihybrid
? Dominant
? Gene
? Genotype
? Heterozygous
? Homozygous
? Monohybrid
? Phenotype
? Recessive
? Trait
Mendel’s work can be summarized in three laws:
??Law of Dominance states that the dominant allele
will prevent the recessive allele from being expressed. The recessive allele will appear when it is paired with another recessive allele in the offspring.
??Law of Segregation (separation) states that gene
pairs separate when gametes are formed, so each
gamete has only one allele of each pair.
??Law of Independent Assortment states that
different pairs of genes separate independently of
each other when gametes are formed.
(Be sure to remember, gametes are sex cells.)
Be sure to remember to review the terms in the box above and study their definitions to gain a better understanding of the concept of heredity through Mendel’s experiments.






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A question on the Biology EOCT may look like this:
Pea plants have seeds that are either round or wrinkled. In this cross, what will be the phenotypic ratio of the offspring?

R R  X R r
R = Round Seeds
r = Wrinkled Seeds
A 50% RR and 50% Rr
B 25% RR, 50% Rr, and 25% rr
C 50% round seeds and 50% wrinkled seeds
D 100% round seeds
The correct answer is D. The genotype of the offspring can be RR, or Rr. Both will result in a round seed, because the phenotype, or outward expression of the genotype, will
express the dominant allele. Answers A and B are incorrect because they are stating genotype, not the phenotype.
Meiosis is the process by which gametes that contain half the number of chromosomes as the parent body cell are produced. Meiosis occurs in two phases, Meiosis I and Meiosis II.
MEIOSIS
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Meiosis occurs only in sex cells. This process consists of two cell divisions but only one chromosome replication.
??The first meiotic division produces two cells containing half the number of double stranded chromosomes. These are called diploid (2n) cells.
??The second meiotic division results in the formation of four cells, each containing half the number of single-stranded chromosomes. These are called haploid (1n) cells.
Remember, male gametes are called sperm; female gametes are called eggs. When a sperm fertilizes an egg, the resulting cell is called a zygote, and the zygote has a diploid
number of chromosomes.
The process of meiosis provides the opportunity for the shuffling of chromosomes and the genetic information they contain. If a cell has two pairs of chromosomes, four kinds
of gametes are possible. It all depends on how the chromosome pairs line up at the equator during meiosis I. When the zygotes are formed, there are 16 possible
combinations that can occur. Let’s look at the pea plant again. Mendel studied seven traits of the pea plant that are carried on seven pairs of chromosomes. Each of these seven
pairs of chromosomes can line up in two different ways producing 128 different combinations of traits. These numbers will greatly increase as the number of
chromosomes increase within a given species. Humans have 23 chromosomes. So the number of different kinds of gametes a person can produce is astounding—more than 8 million! When fertilization occurs, 223 x 223 different zygotes can occur. That is 70 trillion! During meiosis, crossing-over can occur two or three times per chromosome. This results in an endless number of different possible chromosomes. Whether by
crossing-over or by independent segregation of homologous chromosomes, the end result is a reassortment of chromosomes and the genetic information they carry. This is known as genetic recombination. Every so often genes do change. One base may be substituted for another in the DNA
sequence. Sometimes an extra base is inserted or even lost. When something changes the code of a gene, the result will be a change in the protein coded for by that gene. Changes
in the nucleotide sequence of a DNA molecule are known as gene mutations. Some mutations are the result of exposure to mutagens. These are agents such as ultraviolet light, ionizing radiation, free radicals, and substances in tobacco products. Still, mutations can occur in the absence of these mutagens. Spontaneous mutations may occur as a result of replication errors, when adenine wrongly pairs with a cytosine. Also, the enzymes that repair a mistake may “fix” the wrong base.
Base pair substitutions may lead to the substitution of one amino acid for another during protein synthesis. An example of this is sickle-cell anemia, a genetic disorder that has
structural and physiological consequences. A frameshift mutation occurs when one or more base pairs are inserted into a DNA molecule or deleted from it. Remember that polymerases read a nucleotide sequence in blocks of three. A deletion or insertion in a gene region will shift this reading frame, causing an abnormal protein to be synthesized.
Whether a gene mutation is harmful, neutral, or beneficial will depend on how the resulting proteins interact with other proteins and with the environment in which they are
placed.

A question on the Biology EOCT may look like this:
What is a source of genetic variation?
A mutation
B adaptation
C replication
D transcription
The correct answer is A because the two basic sources of genetic variation are mutations and the random assortment of genes that occurs during sexual reproduction. Replication
and transcription are both cellular processes.

??Compare the advantages of sexual and asexual reproduction in different situations??
??Examine the use of DNA technology in forensics,
medicine, and agriculture??
At the mouth of the Saco River in Biddeford, Maine, thousands of mature salmon have returned from the open ocean to travel up river to spawn in the place of their birth. The females have turned red, a color that indicates that they will spawn and then die. The trip up river will be a tough one for the salmon. As the female salmon releases translucent
pink eggs into a shallow nest dug out by her fins in the riverbed, a male salmon comes along and sheds a cloud of sperm that will fertilize the eggs. In about three years the
pea-sized eggs have become salmon, made of billions of cells. A portion of these cells will become eggs or sperm. In time, the life cycle of the salmon will begin again; birth, growth, death, and rebirth. As with any organism, growth as well as reproduction depends on cell division. When a cell divides, its two daughter cells must receive the required number of DNA
molecules. In eukaryotes, DNA is sorted into two nuclei in the process of mitosis. A separate process divides the cytoplasm in two. Mitosis is the process in which threadlike nuclear material is divided equally between two daughter cells. Mitosis keeps the number of chromosomes constant from one cell generation to the next. In eukaryotes mitotic cell division is the main process by which growth and tissue repair is accomplished. Mitosis is also the main process by which single-celled and many multi-celled eukaryotes reproduce asexually.  
Mitosis
Mitosis can be broken into four phases: prophase, metaphase, anaphase, and telophase.
These are briefly described below.
???During prophase, the duplicated chromosomes become distinct and spindle fibers radiate across the cell. The nuclear envelope starts to break up.
???During metaphase, the duplicated chromosomes line up  randomly in the center of the cell between the spindles at the spindle equator.
???During anaphase, the duplicated chromosomes are pulled to opposite ends of the cell. Every chromosome that was present in the parent cell is now represented by the daughter chromosome at the poles.
???During telophase, a nuclear membrane forms around the chromosomes at each end of the cell. The spindle fibers disappear and the chromosomes disperse and become less distinct. Each nucleus has the same chromosome number as the parent cell. The process of mitosis is now complete.
Cytokinesis
At the end of telophase, the cytoplasm begins to divide. In animal cells, the plasma membrane forms a groove and “pinches in” at the middle of the cell. This separates
the two new nuclei and splits the cell in half. In plant cells, the rigid cell wall prevents a groove from forming. Instead, a cell plate forms along the center of the cell and cuts
the cell in half. The cell plate forms new cell walls. Two daughter cells are formed as a result of cytokinesis. They are identical to their parent cell. Cell division allows unicellular organisms to duplicate themselves in a process called
asexual reproduction. In multicellular organisms, cell division allows them to grow (i.e., increase the size of the organism), develop from a single cell into a multicellular organism, and make other cells to repair and replace worn out cells.
Questions on the Biology EOCT may ask you to state the significance of cell division to unicellular and multicellular organisms. A question for this standard might look like
this:
Why is it important for the cells of multicellular organisms to undergo mitosis?
A Mitosis allows for reproduction with male and female gametes.
B Mitosis increases variation within an organism.
C Mitosis produces cells that are different from the original dividing cell.
D Mitosis produces identical cells to the original dividing cell.
The correct answer is D. Multicellular organisms grow in size and replace worn out cells by the process of mitosis. Meiosis is the process that results in gametes which are reproductive cells. Mitosis does not usually contribute to variation within an individual because mitosis normally results in identical daughter cells. Remember that meiosis is another form of nuclear division but occurs only in germ cells set aside for sexual reproduction. Advances in DNA technology have resulted in its increased use in medicine, forensics
and agriculture. Our body’s first defense against injuries and infections is our skin. When a person has third degree burns, bacteria and other harmful organisms can enter the body.
Skin grafts from other parts of the body have been used in the past to help the patient recover. Sometimes it is unsuccessful because the cells that produce new skin have been destroyed. Today, burn specialists can develop cloned skin in about 20 days. They remove a postage-sized piece of unburned skin, cut it into tiny pieces, and suspend the
pieces in a nutrient-rich solution. By the process of mitosis, the skin cells grow into colonies. These colonies continue to grow, forming a thin sheet of skin that is used for
grafting. There are many other uses for DNA technology. Police labs use DNA technology to identify people through a process known as DNA fingerprinting. Plant biologists have
used DNA technology to produce plants with many desirable traits. These include increased disease resistance, herbicide resistance, and increased nutritional content.
Genetic Engineering
Today, researchers use recombinant DNA technology to analyze genetic changes. They cut, splice together, and insert the modified DNA molecules from different species into
bacteria or another type of cell that rapidly replicates and divides. The cells copy the foreign DNA right along with their own DNA. An example of this is the gene for human
insulin. When the gene is transferred into a bacterium, the bacterium will use the “recombined” genetic code to produce human insulin. This is how human insulin is massproduced.
This insulin has saved the lives of many people with diabetes. Not only does genetic engineering have applications in medicine and the environment, it also has uses in industry and agriculture. Sheep are used in the production of alpha-1 antitrypsin, which is used in the treatment of emphysema. Goats are also producing the CFTR protein used in
the treatment of cystic fibrosis. In the plant world, the buds of cotton plants are vulnerable to worm attacks. The buds of a modified cotton plant resist these worms, resulting in increased cotton production. These gene insertions are ecologically safer than pesticides. They affect only the targeted pest.
Scientists today have developed genetically altered bacteria. Among them are strains of bacteria that eat up oil spills, manufacture alcohol and other chemicals, and process
minerals. There is, however, concern about possible risks to the environment and the general population as genetically engineered bacteria are introduced. It is important to remember that recombinant DNA technology and genetic engineering have a great potential for research and application in medicine, agriculture, and industry. As with any new technology, the potential risks must be taken into account, including social, ecological, and environmental risks.

Sample Questions
1 Which of the following is the correct base-pairing rule for
DNA?
A A-U; C-G
B A-G; T-C
C A-T; G-C
D A-C; T-G
2 A mutagenic factor that can alter DNA by the loss of a chromosome segment is known as
A translocation
B crossing over
C deletion
D nondisjunction
3 In Mendel’s experiments with a single trait, the trait that
disappeared in the first generation and reappeared in the next generation is called the
A homozygous trait
B dominant trait
C recessive trait
D heterozygous trait


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5 Changes to an organism’s DNA can cause unexpected traits to be expressed in its offspring. DNA in an individual’s ametes will most likely be altered before being passed to offspring if exposed to
A x-rays
B loud sounds
C magnetic fields
D extreme temperatures
6 Agricultural companies have developed the ability to control the genetic characteristics of their crops. Genetic engineering
techniques have been used to produce all of the following effects except
A grow salt-tolerant crop plants
B decrease harvesting time
C make crop plants resistant to
disease
D decrease soil nitrogen levels
7 In fruit flies, the gray body color (G) is dominant to the ebony body color (g). What is the genotypic ratio of the offspring of a heterozygous gray female and an ebony male?
A % % 25 Gg, 75 gg
B % % 50 Gg, 50 gg
C % % 75 gray, 25 ebony
D 100% gray
8 The process of meiosis produces gametes. How does this process increase reproductive variability?
A Different combinations of alleles are produced.
B Each allele from the parent cell
forms a separate gamete.
C Each pair of genes undergoes crossing-over with different
genes.
D The two genes are passed on to a daughter cell, resulting in new traits.
9 DNA and RNA are nucleic acids. A characteristic of RNA is that it
A  remains in the chromosomes in the nucleus
B  is involved in translating information in DNA into proteins
C undergoes crossing-over during meiosis
D is replicated during the process of mitosis


10 ATG is a DNA triplet that codes for an amino acid. Which mRNA codon will pair with the ATG triplet?
A ATG
B GTU
C TAC
D UAC
Answers
1. Answer: C Standard SB2.a: Distinguish between DNA and RNA According to the base-pairing rules, adenine pairs with thymine and cytosine pairs with guanine; therefore A, B, and D are incorrect. “U” represents uracil, a base found in RNA
but not in DNA.
2. Answer: C Standard SB2.d: Explain the relationship between changes in DNA and potential appearance of new traits The correct answer is C, deletion. Crossing over is the exchange of genetic material by non-sister chromatids, resulting in new combinations of alleles. Nondisjunction is the failure of homologous chromosomes to separate during meiosis. Translocation is the process by which part of one chromosome has exchanged places with the corresponding part of another.
3. Answer: C Standard SB2.c: Using Mendel’s laws, explain the role of meiosis in reproductive variability The correct answer is C, recessive trait. The dominant trait masks or hides the recessive trait. Heterozygous indicates 2 different alleles for a particular trait. Homozygous is having
identical alleles for a particular trait.
4. Answer: D Standard SB2.d: Distinguish between DNA and RNA The correct answer is D. The DNA molecule is best described as a double helix with two strands of nucleotides connected by hydrogen bonds. Option A is a single strand. RNA is a single strand, but has uracil in place of thymine. Option B shows a ring shape. Option C
depicts the double strand, but does not show the twisting pattern. 5. Answer: A Standard SB2.d; Explain the relationship between changes in DNA and potential appearance of new traits. The correct answer is A. X-rays can cause mutations to the DNA in cells. If these cells undergo meiosis to form gametes, the mutated DNA will be passed on to the gametes. Loud sounds, magnetic fields, and extreme  temperatures may damage the cells themselves but are
not known to cause the DNA to mutate.
6. Answer: D Standard SB2.d; Explain the relationship between changes in DNA and potential appearance of new traits The correct answer is D. Genetic engineering has allowed farmers to develop crops that are less likely to be infected with disease, such as fungal infection. Genes from salttolerant marsh plants have been inserted into crop plants to make plants that are salttolerant. Tomatoes have been genetically modified to make them easier to harvest. Plants
have not been modified to decrease soil nitrogen content because high nitrogen content is desirable.
7. Answer: B Standard SB2.c; Using Mendel’s laws, explain the role of meiosis In reproductive variability.
The correct answer is B. Using a Punnett square, the cross can be diagrammed. The female fly is Gg and the male fly is gg. The genotype of the offspring will be 50% Gg and 50% gg. Gray and ebony describe the phenotype, or appearance, of the flies, not the genotype.
8. Answer: A Standard SB2.c; Using Mendel’s laws, explain the role of meiosis in reproductive variability.
The correct answer is A. When cells undergo meiosis, homologous chromosomes separate and each chromosome from the pair ends up in a different gamete, randomly
combined with other chromosomes. This results in many random combinations of chromosomes from the parent cell. Each individual allele does not form a different
gamete. Sections of chromosomes usually cross-over with homologous chromosomes, not individual genes. In meiosis, only one pair of homologous chromosomes is passed on to the daughter cell (gamete), not pairs.
9. Answer: B Standard SB2.a; Distinguish between DNA and RNA The correct answer is B. RNA functions to transcribe the information on the DNA molecule and carry it into the cytoplasm, where it also functions to retrieve the needed
amino acids to form proteins. Therefore, RNA does not remain in the chromosomes in the nucleus. Crossing-over is a process of homologous chromosomes in DNA. DNA is
replicated during mitosis.
10. Answer: D Standard SB2.a; Distinguish between DNA and RNA The correct answer is D. The nitrogenous bases in DNA are thymine, guanine, cytosine, and adenine. Thymine (T), pairs with adenine (A) and guanine (G) pairs with cytosine
(C) in DNA. The nitrogenous bases in RNA are guanine, uracil, cytosine, and adenine. Uracil (U), pairs with adenine (A) and guanine (G) pairs with cytosine (C) in RNA.

Domain IV: Ecology
??Investigate the relationships among organisms,
populations, communities, ecosystems, and biomes??
When you watch the news or read a newspaper it seems that not a day goes by without a story on the environment. “El Nino,” “American Songbirds Vanish,” “Coral Reef Dies in the Virgin Islands.” These are just a few of the headlines that you might have seen. The single thread that connects these very different environments is called ecology. Ecology comes from the Greek word oikos, which means “house.” It is the study of our house, our planet — Earth. Ecology is the scientific study of the interactions between different kinds of living things and their environment. An ecologist is a scientist who studies ecology. The biosphere is the portion of Earth that supports life. Organisms are adapted to survive in a particular environment. Penguins are adapted to live in cold water and ostriches are adapted to live on dry savannahs. They have adaptations for obtaining food, for content will measure your ability to explain the interrelationships between organisms and their environments. Your answers to the questions will help show your knowledge of the following elements:
? Investigate the relationships among organisms, populations,
communities, ecosystems, and biomes
? Explain the flow of matter and energy through ecosystems
? Relate environmental conditions to successional changes in
ecosystems
? Assess human activities that influence and modify the
environment: global warming, population growth, pesticide use,
water and power consumption
? Relate plant adaptations, including tropisms, to the ability to
survive stressful environmental conditions
? Relate animal adaptations, including behaviors, to the ability to
survive stressful environmental conditions protection, and for reproducing.
Two important biological factors affecting living organisms:
Within an ecosystem, two types of environmental
factors can be found: biotic factors and abiotic factors.
All of the living organisms in an ecosystem are known as biotic factors, while the nonliving factors are known as abiotic factors. On the Biology EOCT, you may be asked to describe biotic and abiotic factors and how they interact within an ecosystem.
? Organization of Life ?
Ecologists study the interactions of organisms at five main levels of organization. Yet all the levels are interdependent on one another. To study only one level would not give the ecologist the whole picture.
EXAMPLES OF ENVIRONMENTAL FACTORS
Biotic          Abiotic
Plants          Climate
Animals                 Light
Bacteria                Soil
Water
Organisms — Ecologists will study the daily movements, feeding, and the general behavior of an individual organism. An example would the
Arctic fox.
Populations — An ecologist will study the relationships between populations and the environment, focusing on population size,
density and rate of growth.
Communities — Ecologists will be concerned with the interactions between the different populations in a community and the impacts of additions to or losses of species within communities.
Ecosystems — All biotic and abiotic factors make up the ecosystem. Ecologists will study interactions of the biotic and abiotic factors of an ecosystem with emphasis on factors
that may disrupt an ecosystem.
Biosphere — This is the highest level of organization. It is here where ecologists study the entire planet and the interaction of biotic and abiotic factors on a global level. Examples of biosphere issues would be global warming and human population growth.
TEST CONTENT – CONTENT DOMAIN IV
Population interactions
A population is a group of organisms of one species that live in the same place at the same time. They compete for food, water, mates, and other resources. The way that organisms in a population share the resources of their environment will  determine how far apart the members of the population will live and how large that population will be. Population density is the number of organisms living in a given area. Some organisms, such as tigers, require much space, while others, such as pine trees, can live close together. Keep in mind that some species have adaptations that minimize the competition within a population. An
example would be the frog. The first stage of a frog is a tadpole. Tadpoles are completely different than an adult frog. Their food source is different. They have gills and live in the water. Many insects have juvenile stages that require very different resources than their adult counterparts. This minimizes competition. A population of organisms of one species usually does not live independently of other species. Each population is connected. A community is made up of several populations interacting with each other. This is where balance becomes very important. If there is a change in one population, it can dramatically impact the others living within the community. An increase in one population can cause a decrease in another, sometimes with devastating effects. This change in population size is known as growth rate. A growth rate can be positive, negative, or zero. If a population is provided with ideal conditions, it will increase. Healthy organisms reproduce at a rate greater than their death rate. As long as these ideal conditions
continue, as the population grows larger, the rate of growth
increases. This growth is called exponential growth. This pattern
of exponential growth is in the shape of a J curve. But growth has
limits. If bacteria were allowed to continually reproduce, the
planet would be overrun with bacteria! However, as the population
increases, the resources that are available become limited, and the growth of the population slows and begins to stabilize. This
pattern of logistic growth is an S shaped curve. The point at which the population becomes stable is known as the carrying capacity. It is the maximum, stable population size an environment can support over time. When a population reaches its carrying capacity, a number of factors help stabilize it at that
size. They are called density-dependent and density-independent limiting factors.
Exponential
Growth
Logistic
Growth
Ecologists also study the interactions between populations and their physical surroundings. An ecosystem is the interactions among the populations in a community and the physical
surroundings of the community (also known as abiotic factors). Terrestrial ecosystems are those found on land. Aquatic ecosystems can be fresh or salt water. Salt water ecosystems are also called marine ecosystems. Marine ecosystems occupy 75% of the Earth’s surface! Within each community, particular species have particular jobs to help maintain balance. An example would be a forest community. On the forest floor, there is a decaying log. Fungi have the job of breaking down the organic material from the log. If the log is turned over, you will find worms, centipedes, and beetles also at work. At first glance, it looks like they are all competing for food. But a closer look reveals that they are feeding on different things, in different ways, and at different times. The role that a species plays in its
community is called its niche. A niche includes not only what an organism eats, but also where it feeds and how it impacts the energy flow in an ecosystem. The place where the organism lives is called its habitat. Even though several species may share a habitat, the food, shelter and other resources of that habitat can be divided into several niches. Have you ever heard of blueberries growing in south Texas? Or avocados growing in
Maine? Probably not. Blueberries like a cooler environment whereas avocados grow well in the warm valley of South Texas. Each of these plants is adapted to a particular
ecosystem where they will grow and thrive. Earth supports a diverse range of ecosystems. The type of ecosystem in a particular part of the world largely depends on the climate of
that region. Ecosystems are identified by their climax communities. These are known as biomes. Biomes are the Earth’s major ecosystems. The six terrestrial biomes are listed
below:
1. The tundra biome is found north of the Arctic Circle.
2. The taiga biome is found in a wide band south of the tundra.
3. The tropical rain forests are found in abundance in the Earth’s equatorial zone.
4. Temperate deciduous forests are found in abundance throughout Europe and the eastern United States, between the taiga and the tropical biomes.
5. Desert biomes occur largely in parts of Africa, and the southwestern United States and in parts of Australia, South America, and Asia.
6. Grasslands cover most of South America, Africa, and Australia. Temperate grasslands can be found in central United States, western Canada and across southern Asia.
Density-Dependent Limiting Factors
Competition
Predation
Parasitism
Crowding/Stress
Density-Independent Limiting Factors
Weather
Fires
Droughts/Floods
Human activities
There are also aquatic biomes, divided into fresh water and marine ecosystems. An interesting fact is that only three percent of the water on Earth is fresh water! Ninety-eight percent of the fresh water is found in frozen icecaps! (98% of 3%) Fresh water biomes are the lakes, rivers, streams and ponds. Marine biomes include the open ocean, the rocky intertidal zones, and the estuaries.
Terrestrial Biomes
Tundra
Abiotic Factors: C to C 40 10 ?? ?? - , annual precipitation is less than 25 cm, windy, permafrost.
Biotic Factors: vegetation — nearly treeless, mainly grasses, sedges, and lichens; animals — arctic hare, lemming, Arctic fox, snowy owl.
Tropical Rain Forest
Abiotic Factors: C to C 20 30 ?? ?? , annual precipitation is greater than 200 cm
Biotic Factors: vegetation—broad-leafed evergreen trees, ferns, orchids
animals — monkey, tapir, flying squirrel, birds/parrots, jaguar.
Desert
Abiotic Factors: from C to C 30 38 ?? ?? - in cool deserts to C up to C 20 49 ?? ?? in hot
deserts; annual precipitation less than 25 cm
Biotic Factors: vegetation — brush, cacti, small plants
animals — camels, antelope, rabbits, many reptiles, arachnids
Grassland
Abiotic Factors: C to C 10 25 ?? ?? - , annual precipitation 25 to 75cm
Biotic Factors: vegetation — grasses, small plants, mosses, lichens
animals — grazing herbivores - bison, antelope, zebra, elephant,
wildebeest
predators – wolves, lions, leopards
Taiga
Abiotic Factors: C to C 30 20 ?? ?? - , annual precipitation 30 to 50 cm, soil thaws completely in summer
Biotic Factors: vegetation — coniferous trees, ferns, mosses, mushrooms  animals — snowshoe hare, timber wolf, weasel, black bear, woodpecker
Temperate Deciduous Forest
Abiotic Factors: C to C 10 25 ?? ?? - , annual precipitation 75 to 125 cm
Biotic  Factors: vegetation — sugar maple, birch, pine, oak, flowering plants, moss animals — white-tailed deer, cottontail rabbit, squirrel, raccoon
Marine Biomes
Open Ocean
Abiotic Factors: temperature range is slight, varying with latitude and water depth
Biotic Factors: phytoplankton, fish, dolphins, whales, seals, sea birds
Rocky Intertidal
Abiotic Factors: alternating exposure to sunlight and submergence
Biotic Factors: algae, sea urchins, clams, mussels, starfish
Estuaries
Abiotic Factors: temperature change is extreme
Biotic Factors: algae, mosses, aquatic plants, insects, shrimp, crabs, amphibians, birds
Flow of Matter and Energy through Ecosystems??
• Arranging components of a food chain according to energy flow
Matter and energy are constantly flowing through a stable ecosystem. The primary source of this energy is the sun. Plants and some bacteria harness the energy of the Sun through
the process of photosynthesis. Plants are primary producers. They use the energy they harness from the sun to change simple nonliving chemical nutrients in their environment into living tissues. Plants are also called autotrophs, meaning “self-feeding.”
Because animals cannot harness energy from the sun, they need to eat other organisms to obtain their energy and nutrients. Animals are called consumers. They are also known as
heterotrophs, meaning they need to feed on other organisms. Animals store this energy in their body in the forms of complex carbohydrates, fats, or proteins. Decomposers are
organisms that feed on dead bodies of animals and plants or on their waste products.
Organisms are grouped into trophic levels based on their source of energy – organisms with the same energy sources (Sun, plants, other organisms) are on the same trophic level.

A FOOD CHAIN
Sun ?? grass ?? mice ?? hawk
A FOOD WEB
Consumer Energy Source Example
Herbivore eat plants deer
Carnivore eat other animals lions
Omnivore eat both plants and animals raccoon
Decomposers break down dead organisms bacteria
Because energy cannot be recycled, there must be a way for it to move through an ecosystem. As sunlight hits the Earth, the energy flows first to the tissues of primary producers, then to the tissues of consumers, and finally to the decomposers. This is called
a food chain.
A food chain shows how energy and matter flow through an ecosystem. A food chain is usually four or five links.
On the Biology EOCT, you may be given a diagram of a food chain or web and be asked to describe the role of different organisms. A question for this standard might look like
this:
The correct answer is D. The food chain indicates that hawks feed on snakes. If snakes are removed from the food chain, hawks would be negatively affected because they would have to depend more on other food sources. Frogs would most likely
increase in numbers for a short time in response to not being eaten by hawks.
• Comparing the quantity of energy in the steps of an
energy pyramid A food chain is a simplified way for ecologists to study how energy and matter flow. But it is not always that simple.
In the food chain below, which population will most likely decrease if snakes are
removed from the food chain?
grass ?? grasshopper ?? frog ?? snake ?? hawk
A grass
B grasshopper
C frog
D hawk
Relationships exist between organisms that feed on more than one species. In an actual ecosystem there are many more plants and animals involved. Ecologists call this more complex interconnected system a food web Ecologists use energy pyramids to show how energy decreases at each succeeding trophic level. The total energy transfer from one trophic level to the next is only about 10%. Not all the food that is captured is actually eaten and digested. Some of the digested food is
used by that organism as a source of energy. Every time an organism eats another, much of the energy is used up rather than being stored. Some of the energy is lost as heat. Also,
ecologists construct energy pyramids based on the population size at each trophic level.
This shows how some populations will decrease at each increasing level.
• Explain the need for cycling of major nutrients (C, O, H, N, P).
Unlike energy, matter is recycled in an ecosystem. Matter cycles from one organism to another. Matter cannot be replenished in an ecosystem, like the energy from the sun. For example, in the water cycle, water passes from the atmosphere to the land or water surfaces through precipitation and then eventually returns to the atmosphere. Carbon is found in the environment as carbon dioxide gas. From the atmosphere, CO2 is used in photosynthesis to form sugar. Respiration and decay are two ways that carbon returns to the atmosphere as a gas. Carbon also returns to the atmosphere when fossil fuels are burned. Atmospheric nitrogen makes up 78% of our air, but it is in a nonusable form.
Lightning and some bacteria are able to convert atmospheric nitrogen into usable nitrogen-containing compounds. Plants use these nitrates and ammonium compounds in their growth. Herbivores eat the plants and convert nitrogen-containing plant proteins into nitrogen-containing animal proteins. Organisms return nitrogen to the atmosphere when they die and decay. Phosphorus cycles through the environment in two ways. Plants get phosphorus from the soil. Animals get phosphorus from the plants they eat. When the animals die, they decompose and the phosphorus is returned to the soil. The other way that phosphorus is cycled is a long term cycle. Phosphates that are washed out to sea become incorporated into sediments as insoluble compounds. When the sediments become exposed, the phosphorus can be recycled again into the environment.
On the Biology EOCT, you may be asked to describe the interactions of biotic and abiotic factors in the various cycles.
A sample question on the Biology EOCT may look like this:
The correct answer is D, phosphorus. It cycles two ways in the environment, one short-term and one long-term cycle.
Spotlight on the Standards
??Relate environmental conditions to successional
changes in ecosystems??
Succession
Ecosystems are alive and constantly changing. Some changes happen quickly, such as a forest fire or flood or even when a volcano erupts. Some happen slowly over a period of time as new saplings grow into tall mature trees. When an ecosystem changes, the organisms in that ecosystem may need to change to survive. Succession is the natural change that takes place within a community of an ecosystem. There are two types of
succession that ecologists study.
Primary succession happens when one community is completely destroyed and a new one emerges. An example is the changes that take place after a volcano erupts and the lava flow stops and cools. In 1963, scientists were able to observe the birth of a new
volcanic island, named Surtsey. The island measured 1 square mile. Seabirds were the first to arrive. Seeds, whether they were airborne or came as “hitch-hikers” on the feathers of the birds, or from the ocean tides, then reached the island. The first plant, a sea rocket, bloomed in 1965! Spiders were visible, and lichens and mosses soon grew. As these pioneer organisms died, their remains formed soil and later, seals used Surtsey’s beaches to have their young. However, over time, Surtesy has lost about one-fourth of its mass, due to erosion. One day the island may completely disappear. It has given scientists an in-depth look at how a community is developed and then destroyed.
Eventually, primary succession slows down and the community becomes stable. This community is known as a climax community. Secondary succession n occurs when a natural disaster or human activity destroys a community. It is like primary succession, in
that the community of organisms inhabiting an area changes over time. However, when secondary succession takes place, soil is already present. In secondary succession, the species replacing the pioneer species are different. It also takes less time to reach a climax community.
One essential element that has two different cycles is
A water
B carbon
C nitrogen
D phosphorus
In Yellowstone National Park, thousands of acres burned as a result of a lightning strike. This was another opportunity for scientists to study secondary succession first hand. It
was surprising to see wildflowers pop up first. They were not able to grow under the forest shade. Within three years, flowers, grasses, ferns, and saplings began to take hold and grow. Once the saplings begin to grow, they once again will shade the forest floor and a mature forest will develop.
Spotlight on the Standard
??Assess and explain human activities that influence
and modify the environment??
In today’s world there is a high demand for resources in order for living things to survive. There are natural resources that we use everyday, without realizing it. When we turn on a light to read a book that is made from paper we are using natural resources. They include soil, plants, water, crops, animals, gas, and oil. A natural resource that is replaced or replenished by natural processes is known as a renewable resource.
Nonrenewable resources are those that are available only in limited amounts. Once they are gone, they are gone! Metals, such as tin, silver, gold, uranium, and copper are some examples of nonrenewable resources. Minerals, such as phosphorus, are recycled so slowly in the environment that they are considered nonrenewable. Topsoil is also considered a nonrenewable resource because it takes hundreds of years to develop from
decomposed plant material. Fossil fuels are always being formed but they too are considered nonrenewable because they form over long periods of time. Humans use them faster than they can be replaced.
Extinction is the complete disappearance of a species. The list of extinct species grows longer every year. Within the last twenty years, it is estimated that 30 species of plants and animals have become extinct in the United States alone. Some extinctions happen because of natural disasters but many, if not most, are due to human activity. Species that are declining rapidly are considered to be a threatened species. An example is the
African elephant, pursued for its ivory tusks. A species is considered endangered when its numbers drop so low that extinction is almost inevitable. In the Florida Keys, the
manatee is endangered because of boating and loss of habitat. In California, the condors are endangered due to several human-caused factors.  One of the major ways humans impact the environment is pollution, which is probably one of the greatest threats to living things. Pollution is the contamination of soil, water, or air and is a result of human activity. Any substance that is harmful or is a waste product is a pollutant. A pollutant can be a substance in the wrong place or in the wrong concentration. Although pollution has been around for many years, it has increased worldwide as more countries have become industrialized. Pollution affects living organisms, including humans, as well as the physical environment. Cow and horse manure can be considered a good plant fertilizer. But if too much manure is produced due to overcrowding and the decomposers cannot break the manure down as fast as it is produced, large amounts of nitrogen run off into waterways. This nitrogen will increase
the growth rate of algae in these water systems, causing a decrease in the amount of oxygen in the water. This can result in the death of the fish, insects, and other animals in the water.
Air pollution is caused primarily by the burning of fossil fuels to produce electricity. However, the burning of fuel for other activities such as driving cars, heating homes, flying planes, and generating electricity has also contributed to air pollution. Examples of air pollutants include dust, smoke, ash, carbon monoxide, and sulfur oxides. Smoke that is released by burning fuels contains gases and particulates. These are solid particles of
soot that can harm living organisms now or have an impact later in their life. Workers in coal mines develop black lung disease from breathing in the dust from the coal. A combination of smoke, gases, and fog is called smog. Smog containing sulfur oxides
reacts with water vapor in the atmosphere to produce sulfuric acid. This sulfuric acid falls to the ground as acid rain, which damages crops, kills organisms in aquatic ecosystems,
and erodes buildings and monuments. Acid precipitation leaches calcium, potassium and other valuable nutrients from the soil, making the soil less fertile. This causes a decrease in the amount of living things that can grow (plants, trees, ferns). It also has a great effect  on lake ecosystems causing a decrease in the pH level. This excess acidity disrupts the natural balance of the organisms living there. Another form of air pollution is the increased production of carbon dioxide. When fossil
fuels, like oil, coal, and natural gas, are burned, carbon dioxide is released into the atmosphere. Excess carbon dioxide in the air can contribute to the greenhouse effect, which is believed to cause global warming. Gases in the atmosphere trap much of the
radiant energy from the sun that reaches the surface of the Earth. The surface of the Earth heats up and radiates back into the atmosphere. The atmosphere prevents much of this
heat from escaping. This is known as the greenhouse effect. If this process did not happen, the Earth would be too cold for any living things to survive. All the Sun’s energy would be radiated back into space. The ozone layer that surrounds the Earth prevents lethal doses of ultraviolet radiation coming in from the sun from reaching organisms here on the Earth. Scientists have discovered that the ozone layer is thinning due to the release
of CFC’s (chlorofluorocarbons) into the atmosphere. CFC’s are manufactured for coolants in refrigerators and air conditioners, and used in making Styrofoam. Water pollution is caused by contaminants from sewers, industries, farms, and homes,
which enter water sources such as lakes, rivers, groundwater, and oceans. Sewage, chemical wastes, fertilizer, and dirty wash water can enter lakes, streams, rivers, and eventually the oceans. Pollutants that trickle down through  the soil can make their way to the underlying groundwater, which is the source of drinking water for some people. Humans are, however, becoming more aware of the possible negative effect they have had on the environment and are trying to offset past damage. As a result, greater efforts are being made to conserve energy resources, protect and conserve material resources, and to control pollution. For example, wildlife conservation efforts protect species from
habitat loss, over-hunting, and pollution. People are making an effort to conserve energy by limiting the use of energy resources
like fossil fuels through the increased use of public transportation and carpooling.  Another way energy resources are being conserved is to reduce energy waste by making
homes and buildings more energy efficient. Using alternative forms of energy can also conserve energy resources. For example, solar energy and wind energy provide an unlimited supply of energy with minimal impact on the environment.
You’ve probably heard of the “three R’s” of conservation: reduce, reuse, and recycle. Reducing, reusing, and recycling resources can decrease the amount of new material taken from the earth. For example, buying products in recyclable packages or products
that can be recycled helps conserve material resources. Another way to conserve material resources is to reuse materials instead of throwing them away.  What happens to the materials that are not recycled or cannot be recycled or reused?
They probably end up in the garbage, which is hauled to a landfill to be buried underground. In a sanitary landfill, layers of compacted garbage are spread between layers of soil and eventually covered with grass and other plants. New techniques of sanitation and waste disposal are also being developed.
Glaciers contain more fresh water (2.15%) than any other fresh water source on Earth. If glaciers and other bodies of fresh water ice melted, low coastal regions would be flooded by the rising ocean water. Some fossil records might be destroyed, but this would not be a major consequence. The ocean would become less salty, not more salty, as it was diluted with fresh water. The melting of glaciers would not cause an increase in atmospheric carbon dioxide, but increasing atmospheric carbon dioxide could contribute to further warming.
The theory of global warming suggests that a trend toward warmer temperatures on Earth will cause glaciers to lose mass. A major consequence of glacial melting is
A flooding coastal regions
B destruction of fossil records
C increased saltiness of the ocean
D increase in atmospheric carbon dioxide
The answer is A
??Relate plant adaptations, including tropisms, to the ability
to survive stressful environmental conditions??
Even though plants don’t have a nervous system, they do possess mechanisms that enable them to respond to their environment. These responses are known as tropisms. It is a Greek word, which means, “to turn.” Plants will shift the positions of their roots, stems, leaves, and flowers in response to environmental conditions such as sunlight, temperature, water, and gravity. There are several types of tropisms. Geotropism is the response of seedlings to the force of gravity. It is important when seeds are sprouting. Geotropism causes the roots to grow downward and the stems to grow upward, no matter what the position of the seed may be when it is planted. Phototropism is the ability of
the plant to respond to light. If a plant is placed near a window or another light source, the plant will grow in the direction of the light source. A phototropic response can happen so quickly that even a seedling will respond within a few hours. Thigmotropism is the response of a plant to touch. Climbing plants, ivy, and vines use thigmotropism in order to find their way up or around a solid object for support. It is also used by some plants for
protection. Some plants respond to other stimuli from the environment such as length of day and the seasons. Some flowers bloom once a year, while some others, like some cacti, bloom at night. So how do plants control their growth in response to environmental stimuli? Most plants do this by way of chemical messengers known as hormones. A hormone is a chemical
that is produced in one part of an organism and transferred to another part to affect the activities of that part of the plant. One type of hormone is called auxin. Auxins are responsible for regulating phototropism in a plant by stimulating the elongation of cells. The cells on the auxin-rich shaded side of a stem will grow longer than the cells on the other side, causing the stem to bend toward the light. High concentrations of auxin help promote the growth of fruit and minimize the falling off of fruit from the plant. When the auxin concentrations decrease in the autumn, the ripened fruit will fall. The plants will begin to lose their leaves. Gibberellins are growth hormones that cause plants to grow
taller. They also increase the rate of seed germination and bud development. There are Tropism—a plant’s response to their
environment Geotropism—a plant’s response to gravity
Phototropism—a plant’s response to light
Thigmotropism—a plant’s response to touch certain tissues in the seeds that release large amounts of gibberellins to signal that it is time to sprout. There are also hormones that do the opposite; they inhibit plant growth and cell division.
Abscisic acid is one of these. It inhibits plant growth during times of stress, such as cold temperatures or drought. In studying these hormones, scientists have found that it is the
balance of different hormones that determines the plant growth, rather than one hormone by itself.
Examples of Adaptations
Seeds of many plants will go dormant in unfavorable conditions. In a drought period, many will lay dormant until the rains come. Then they will sprout. Roots and stems are modified in many plants into storage organs in order to survive through winter underground. Tulips, daffodils, and crocuses are a few examples. Many trees drop their leaves and go dormant for the winter. Conifers have needles instead of leaves. The leaves have a waxy coating over them to reduce the amount of evaporation that takes place and
to conserve water. The bark on the conifers is thick, helping to insulate the tissues inside. These adaptations help the conifers to continue their life processes even in below freezing
temperatures. The branches of the conifers are flexible, allowing for them to bend instead of break under the weight of ice and snow.  Flowers can be pollinated in a number of ways, by the wind, insects, birds, and animals, even bats. Maple trees produce seeds that are shaped like a wing. They have the nickname of “helicopters.” They can be carried over long distances by the wind. Some plants produce seeds that have hooks or barbs on them that attach to the fur of passing animals. These have the nickname of “hitchhikers.” Many flowers that depend on insects
for pollination are brightly colored and fragrant, to draw attention to them. Pollen will rub off on the insect and they will carry it to another flower. The coconuts from palm trees
float. They will travel from one beach to the next or even from one island to another.
What characteristic of some pine trees allows the species to survive disasters?
A modified leaves form needle bundles
B seeds that germinate after fires
C pollen that is easily carried by wind
D bark that is lightly colored
A question for this standard may look like this:
The correct answer is B. Several species of pine have seeds that are resistant to fire. They are in cones that must be exposed to fire to open and release the seeds. The modified leaves conserve moisture. The pollen blows easily, therefore insect and bird activity isn’t necessary to spread the pollen from tree to tree. The color of the bark does not make the tree resistant to disaster. Bark thickness is a more important characteristic.
Remember to review your textbook for further study of plant adaptations to environmental conditions. Questions on the EOCT may ask you to describe certain characteristics of adaptations that plants have undergone in order to survive.

??Relate animal adaptations, including behaviors, to the ability
to survive stressful environmental conditions??
Behavior Behavior is defined as anything an animal does in response to a stimuli in its
environment. Squirrels gathering nuts and acorns in the autumn is a behavior that is
stimulated by shorter days and colder weather. Animals have a busy life! Gathering food
for themselves and their young, caring for their young, avoiding predators, seeking
shelter, and finding a mate, are important to the survival of animals. How do they know
what to do and where to go?
Inheritance plays an important role in an animal’s behavior. An animal’s genetic makeup
determines how it will respond to certain stimuli. Scientists have found that an animal’s
hormonal balance, in combination with its nervous system, affects how sensitive an
animal is to certain stimuli. Inherited behavior of animals is known as innate behavior. It
includes both automatic responses and instinctive behaviors. When you touch a hot
surface, you automatically draw your hand away from the source of heat. When
something flashes in your face, you automatically blink. These behaviors are known as
reflexes. They are the simple, automatic responses that require no thinking at all. You
just respond.
Instincts are a complex pattern of innate behaviors. Reflexes can happen within a
second. Instinctive behaviors may take longer and may be a combination of behaviors.
An animal’s courtship behavior is instinctive. Animals will recognize certain behaviors
exhibited by members of the same species. Each species has its own courtship behaviors.
The male and female black-headed gull dance in unison side by side and turn their heads
away from each other. The female taps the male’s bill and he gives her a regurgitated
fish! Then the courtship is over and the pair will mate. Different species of fireflies flash
distinctive patterns of light. The female will respond only to the male that exhibits the
species-correct flashes.
Territorial
A territory is a physical space that contains the breeding grounds, feeding area, shelter
or potential mates of an animal. Animals that have territories will defend their space,
whether it is against an animal of the same species or a different one. Setting up
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territories is a way to reduce conflict, control populations, and decrease competition. It
also is a problem solver in that it helps provide for efficient use of environmental
resources by spacing animals out over an area. There is a greater chance for survival of
young, increasing the survival rate of the species.
Aggression is another behavior exhibited by animals to fend off predators and
competitors. It is a way to protect young and to protect food sources. Animals of the same
species will not usually fight to the death. Fighting is often more symbolic than anything
else. Usually it will be the stronger animal that will stop the fighting and the weaker
animal will show signs of submission.
Migration
Migration is the instinctive, seasonal movement of a species. Over half of the birds that
nest in the United States fly south for the winter. Many head to South America where
food is more abundant during the winter months. Then they will fly north in the spring to
breed. Some species of whales do the same. Arctic terns migrate between the Arctic
Circle and Antarctic. This trip calls for great endurance and strength in the little birds.
How do they know where they are going? Animals migrate in a variety of ways.
Scientists believe that some use geographical clues such as mountain ranges. Others may
use the Earth’s magnetic field.
Scientists have also found that migration is triggered in part by hormones that are
produced in response to environmental changes, such as changing day length. Migration
also takes place in response to changing environmental conditions, such as overcrowding
or reduced food supplies. Yet, not all animals migrate. How do these other animals cope
with a changing environment?
Many animals undergo physiological changes that reduce their need for energy. Some
animals and birds go into hibernation during the cold winter months. Hibernation is a
state in which the body temperature drops, oxygen consumption decreases, and breathing
rates decrease to just a few breaths per minute. Estivation is a state in which animals
reduce the rate of their metabolism due to extreme heat, lack of food or long periods of
drought.
Learned behavior
Learned behavior is a result of previous experiences of an animal. It has survival value
because it allows animals to change their behavior in a changing environment. It allows
the animal to adapt in order to increase its chance for survival. Feral horses learn to allow
people to ride them. Deer have learned to come into yards to feed with no fear of people
or barking dogs. This type of learned behavior is called habituation. It occurs when an
animal is repeatedly given a stimulus that is not harmful and does not have a negative
impact on the animal. Imprinting is another form of a learned behavior. An example is
when an animal returns to the place of its birth to lay its eggs or when an animal imprints
on its mother or other organism in its environment. Kemp Ridley sea turtles will return to
the beach where they were hatched to lay their eggs. It is not yet known exactly what the
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turtles imprint on, whether it is the sand, or in the water. Salmon also return to the same
river to spawn. Out of a herd of zebras, a young zebra can find its mother with no
problem.
Adaptations for Defense
Most species of plants and animals have adaptations that serve as a defense against a
predator or as a means of escape. They fall into two categories: mechanical defense and
chemical defense.
Mechanical defense is incorporated into the physical structure of the organism.
Chemical defense occurs when the animal produces stinging sensations, paralysis,
poisoning, or just a bad taste.
Mechanical Defenses
Many animal defenses are physical structures such as claws, sharp ivory tusks, stingers,
and shells. Octopuses have liquid ink that they squirt out as a curtain to escape behind.
Sometimes it’s just an animal’s size that is enough to deter a predator from attacking.
Plants also have their own mechanical defenses. Many have thorns, spines and stiff hairs
that repel a predator. Some grasses in the African savannahs have a thick deposit of silica
that wears away the teeth of grazing animals. However, some of these animals have
counteradapted and have developed large, hard molars that resist the abrasive action of
the mineral.
Chemical Defenses
Chemical defenses are used in a variety of strategies for deterring predators. Many
marine organisms have neurotoxins in their tissues that attack the nervous system of their
attackers. Bombardier beetles shoot out a boiling hot chemical combination of hydrogen
peroxide and a boiling solution of quinines. Other chemical defenses include poisons and
venoms, which are used by snakes, toads and stinging bees and wasps. Some animals
take on the chemical defenses of other species. The monarch butterfly is a great example.
As larva, monarchs feed on milkweed plants, which contain cardiac glycosides, which are
poisonous to vertebrates and many insects. After pupation, the tissues of the adult
monarch are saturated with the chemicals. Birds that eat the monarch will vomit
violently. This is a way of ensuring the monarch’s survival.
Chemical defenses in plants come in a number of ways. Some plants contain chemical
compounds that taste bad, while others contain sap that is an irritant or poison. Another
defense is nutrient exclusion. Some plants aren’t worth eating because their tissues are
lacking a sufficient amount of nutrients.
Another defense is camouflage. It involves colors and patterns that enable the organism
to blend into its environment or appear to be something they are not. Cryptic coloration
is when an organism has the same color or pattern as its background. Gecko lizards, tree
frogs and leafhoppers are a few examples. Disruptive coloration is another example
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where an organism’s silhouette is broken up by color patterns. Countershading is when
an organism is two toned. Light and dark colors reduce the visual cues to predators.
Many ocean fish are dark on top and light on the bottom. Predators on top can’t see the
fish against the dark waters below.
We have covered a lot of information on plant and animal adaptations. Remember to
review your textbook for further study.
On the Biology EOCT, you may be asked to describe certain behaviors or characteristics
of plant tropisms, animal behavior, and survival strategies of organisms as they relate to
their environment.
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Sample Questions For Content Domain IV: Ecology
1 A group of organisms of a certain
species that is in one area at a
given time is know as a (an)
A ecosystem
B community
C population
D trophic level
2 As energy flows through an
ecosystem, at each trophic level it
A increases
B decreases
C fluctuates
D remains the same
3 Predators often feed on weak or
sick animals in an ecosystem. The
role of the predator is described as
its
A community
B habitat
C niche
D population
4 The dodder is a land plant that
parasitizes other plants. It grows
in long thin strands that penetrate
the host plant and absorb water,
minerals and carbohydrates.
Unlike other land plants, the
mature dodder does not require
A nutrients
B water
C air
D sunlight
5 The state of California has several
large cities and very productive
croplands that divert and use large
amounts of water from rivers.
What is one damaging effect of this
use of water from the rivers?
A increased amounts of solid waste
pollution in the oceans
B decreased amounts of fresh
water in marshes and estuaries
C changes in local rainfall amounts
D changes in upstream water tables
6 Plants that live in the rainforest
have many adaptations to their
environment. Some plants such as
vines have adaptations which
allow them to attach themselves to
the trunks of trees. These
adaptations allow vines to
successfully compete for which of
the following limiting resources in
the rainforest?
A sunlight
B water
C carbon dioxide
D oxygen
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7 Lightning causes a fire that
destroys all the plants in a forest
community. Which of the
following is most likely to be the
first to occupy the burned area?
A oak seedlings
B pine trees
C grasses and annual plants
D woody shrubs
8 Pilot fish and sharks have a
relationship where the pilot fish
eats bits of food that the shark
drops or leaves behind. The shark
is unaffected by the pilot fish
behavior. Which of the following
best roles describes the pilot fish?
A predator
B herbivore
C scavenger
D parasite
9 Birds have been observed puffing
up their feathers under certain
conditions. By trapping air
between feathers, this behavior
helps the bird
A hide from enemies
B expend less energy during flight
C shelter offspring
D trap body heat
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Answers to Sample Questions in Content Domain IV
1. Answer: C Standard SB4.a: Investigate the relationships among organisms,
populations, communities, ecosystems, and biomes
The correct answer is C, population. An ecosystem consists of all biotic and abiotic
factors. A community consists of several populations living in an area. Trophic levels
have to do with energy pyramids. One trophic level can include many species.
2. Answer: B Standard SB4.b: Explain the flow of matter and energy through
ecosystems by
?? Arranging components of a food chain according to energy flow
?? Comparing the quantity of energy in the steps of energy pyramids
?? Explaining the need for cycling of major nutrients (C, O, H, N, P)
The correct answer is B. As energy is transferred up the energy pyramid, remember that
only about 10% of the energy moves to each successive level. The rest of the energy is
used by the organisms themselves or is given off as heat.
3. Answer: C Standard SB4.a: Investigate the relationships among organisms,
populations, communities, ecosystems, and biomes
The correct answer is C. The community describes the different populations in an
ecosystem while population describes all individuals of the same species. The niche of
any organism is the functional role within the ecosystem. A habitat is the physical
environment of an organism.
4. Answer: D Standard SB4.e Relate plant adaptations, including tropisms, to the
ability to survive stressful environmental conditions
The correct answer is D. Since the dodder is able to get water, minerals and
carbohydrates from other plants, it can survive without sunlight for photosynthesis. The
dodder does require air for cellular respiration.
5. Answer: B Standard SB4.d Assess and explain human activities that influence
and modify the environment such as global warming, population growth, pesticide use,
and water and power consumption
The correct answer is B. The rivers flow into marshes and estuaries and excessive water
use results in a decreased amount of fresh water and increased salinity in the marshes and
estuaries. The primary cause of solid waste pollution in oceans is dumping of garbage.
The use of water from rivers has not been found to significantly affect local climate
conditions. The underground water tables in upstream watersheds are not impacted by
downstream water use.
Biology EOCT TEST CONTENT – CONTENT DOMAIN IV
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Copyright © 2005 by the Georgia Department of Education. All rights reserved.
6. Answer:B Standard SB4.e Relate plant adaptations, including tropisms, to the
ability to survive stressful environmental conditions
The correct answer is A. The tree canopy of rainforests blocks most light from reaching
the ground. The vines have adapted in ways that make it possible for them to live in a
part of the rainforest that has more available light.
7. Answer: C Standard SB4.c Relate environmental conditions to successional
changes in ecosystems
In most ecosystems, secondary succession begins with grasses and annual plants, whose
seeds either are fire-resistant or carried easily on the wind or by animals. These plants
are then followed by shrubs and perennial plants, then by trees.
8. Answer: C Standard SB4.a Investigate the relationships among organisms,
populations, communities, ecosystems, and biomes
The correct answer is C. Since pilot fish eat what the shark leaves behind, it is best
described as a scavenger. Pilot fish do not obtain food by hunting, meaning it is not a
predator. Since the pilot fish eats only pieces of food left by the shark, it does not eat
plants. The pilot fish is not a parasite since the shark is unharmed in the relationship.
9. Answer: D Standard SB4.f Relate animal adaptations, including behaviors, to the
ability to survive stressful environmental conditions
Rationale: The correct answer is D. Air trapped between feathers acts as an insulator.
Puffing up will not help the bird become less visible, fly faster, or act more protectively.
Biology EOCT TEST CONTENT – CONTENT DOMAIN V
69
Copyright © 2005 by the Georgia Department of Education. All rights reserved.
Content Domain V: Evolution
Spotlight on the Standards
??Trace the History of the Theory??
The Origins of the Theory
When we think of evolution, our minds often relate that thought to the name of Darwin.
But the concept of evolution began much earlier than Darwin. In fact in 1809, the year
that Darwin was born, a French zoologist named Jean Baptiste de Lamarck presented a
new evolutionary theory. Lamarck believed that all life forms evolved and that the
driving force of evolution was the inheritance of acquired characteristics. He believed
that organisms changed due to the demands of their environment. This “passing on of
acquired characteristics” helped lower life forms climb the ladder of life to become more
complex organisms. The example that he used in explaining his theory is that of a
giraffe’s neck. He believed that in order for the giraffe to reach its food, it had to stretch its neck. So, over many generations, an elongated neck became part of the giraffe’s makeup. He also believed that if a body part of an organism wasn’t used, that body part would be lost. We know today that his theory was a little off. But it does have an important relationship to Darwin’s theory, that is, that evolution of living things proceeds according to natural laws.
A LOOK AT CONTENT DOMAIN V
Test questions in this content domain will measure your
knowledge and understanding of the role of natural selection
in the development of the theory of evolution. The questions
will assess your understanding of and ability to:
? Trace the history of the theory
? Explain the history of life in terms of biodiversity, ancestry,
and the rates of evolution
? Explain how fossil and biochemical evidence support the
theory
? Relate natural selection to changes in organisms
? Recognize the role of evolution to biological resistance
Geologists were also discovering ancient bones, shells, and fossilized plants in England in the late eighteen hundreds. They were finding these remains on hillsides and in riverbeds. These findings caused people to look for an explanation for the existence of the fossils. This new revolutionary concept of evolution would soon become a fundamental theory, explaining the diversity of organisms.
Darwin
Before Darwin ever set sail on the HMS Beagle, he was already preparing himself by reading Charles Lyell’s Principles of Geology. Lyell proposed that plant and animal species had arisen, developed variations, and then became extinct over time. He also believed that the Earth’s physical landscape changed over a long period of time. Darwin read an essay written fifty years before his time by a man named Thomas Malthus called The Principles of Population. In it, Malthus proposed that populations outgrew their food
supplies, causing competition between organisms and a struggle for one species to survive against another. But the most important impact on Darwin was his 40,000-mile trip on the Beagle. What an adventure it must have been for this naturalist! Darwin found a vast treasure of fossilized bones of extinct sloths and giant armadillos in Patagonia. He saw a variety of plants and animals that were very different due to their geographical
location. But when Darwin reached the Galapagos archipelago, the world burst open before him with an amazing variety of life.
It was here that he found large iguanas swimming in the ocean and eating seaweed! Lizards have always been terrestrial reptiles in warm environments. What were they doing in the ocean? He also found giant tortoises with carvings on their backs from
whalers that had passed through a hundred years before. He saw different variations of mockingbirds and other bird species.
From all the information gathered by Darwin, two central concepts emerged to form the basis of his theory of evolution.
First, Darwin observed that variations within a species were dependent on the environment. Adaptations are genetically coded traits that occur in organisms and enable them to be more successful in their environment. Darwin reasoned that the importance of these adaptations is to ensure the survival through reproduction of that species. The organisms that lack these adaptations will not reproduce as successfully. Secondly, the organisms on the Galapagos Islands had become geographically separated from one another. This resulted in reproductive isolation. There is no interbreeding between organisms of the same species that are located on different islands. For example,
finches on one island could not cross with finches of the same species on another island. He theorized that within a population of a species, adaptations would arise due to reproductive isolation. The organisms would develop adaptations to their environment  over time that would result in significant differences between the same species on different islands.
But while Darwin was composing his theories of evolution, another man by the name of Alfred Russel Wallace was also formulating his own theory of evolution. He studied plants and animals in Brazil and in Southeast Asia. Wallace’s emphasis was based on the
idea of competition for resources as the main force in natural selection. Darwin focused on reproductive success. It was the tremendous amount of data gathered by Darwin that
supported his idea, and the comprehensive explanation that he put together became the evolutionary theory. What is even more interesting is the fact that Darwin knew nothing about genes or genetics. He was missing the connection between heredity and differences in the characteristics of organisms. Mendel’s work was not published until 1866, and it wasn’t appreciated for decades. It wasn’t until the rediscovery of Mendel’s work that scientists were able to put together the concepts of natural selection with genetics. This opened the door for scientists to account for phenotypic variations in populations. It is where
scientists derive the term population genetics. It is an area of biology in which researchers use mathematical descriptions of genetic phenomena to help them trace evolutionary trends within populations. Natural selection is a mechanism that explains changes in a population that occur when organisms with favorable variations for that particular environment survive, reproduce
and pass these variations on to the next generation.
A question for this standard on the Biology EOCT may look like this:
Ancestors of the koala lived on the ground, but modern koalas live in trees and
eat eucalyptus leaves, which are poisonous to most other animals. The difference
between the ancestor and modern koalas was caused by
A the presence of homologous structures
B the presence of vestigal organs
C selective breeding
D natural selection
The correct answer is D. Koalas changed gradually over time through the process of natural selection to fit a niche in which there was little competition for food or habitat. Homologous structures and vestigal organs are a result of evolution, not a cause. Koalas were not selectively bred by humans to have the traits they have today.




Explain the History of Life in Terms of Biodiversity,
Ancestry, and the Rates of Evolution??
Ever since Darwin and his theory of evolution and Mendel with his genetics, scientists have come to the conclusion that all organisms on Earth are somehow related. Some animal relationships are easier to observe than others. Scientists have coined the term adaptive radiation when diversity seems to have occurred in a newly evolved species in a relatively short time. They also believe it occurs when an organism colonizes a new
area in which there is another organism that is lacking in survival skills. Researchers use the example of the finches Darwin observed on the Galapagos Islands. He counted over a dozen different kinds of finches that he believed evolved from a single founding species. A similar, but opposite concept is that of convergent evolution. This is where unrelated species may independently evolve superficial similarities, because of their adaptations to the same environment. These connections are valid in their own way but they still have their limitations as to tying together the relationships that organisms have with one
another. It wasn’t until molecular biologists developed new techniques for analyzing DNA that a major connection was made. As more and more data were gathered, evolutionary biologists became intrigued with DNA and the information that it provided
about the relationships between organisms. Data collected show that segments of DNA and even entire sequences of the amino acids in some proteins seem to be identical in many organisms. One structure in particular that is of great interest is the ribosome. Molecular biologists have found that the DNA sequences that build bacterial ribosomes are similar to the genes that direct the assembly of human ribosomes. Another interesting connection they found was myosin. Myosin is a protein found in muscle cells of humans and other multicellular organisms. Myosin reacts with other proteins to cause muscles to contract, causing movement. The interesting point is that myosin is also found in yeast cells. Do yeast cells have muscles that make them move? No, not really. But they do have parts within the cell that require movement. This is accomplished when the myosin
interacts with other proteins to make that movement possible. So, how can these similarities be explained? The original form of myosin made it possible for parts of the cells to move. As life diversified, the original myosin genes evolved into forms that help
our bodies move. This similarity between genes and DNA shows that once life began, it diversified by evolving, combining, and mixing up the makeup of living organisms. This has culminated in what scientists call biodiversity.

Biodiversity is the variety of organisms, their genetic information, and the biological communities in which they live. Researchers use three different terms when talking about
biodiversity: Is it possible, then, to determine how long ago genes branched off from a common ancestor? In theory, DNA changes should occur at a constant rate. In reality, it is complicated by a number of factors. Different positions in DNA sequences acquire
mutations faster than others. It seems that different branches on the evolutionary tree acquire mutations at different rates. Some genes are under a more intense pressure from natural selection not to change. So, in order for researchers to time recent evolutionary events, they must use “time clocks” that tick fairly quickly. But to estimate how long ago there was a shared ancestry, they must use clocks that tick very slowly.
Speciation is the evolution of a new species that occurs when interbreeding happens, or when the production of fertile offspring is prevented. In the physical world, natural
barriers form and cause the breakup of populations to form smaller populations. Volcanoes, sea-level changes, and earthquakes are a few examples of natural occurrences that affect populations. This is known as geographical isolation. Geographical isolation prevents interbreeding, so gene exchange will cease. So over time, each smaller population will adapt to their new environment through the process of natural selection.
Eventually, this causes the gene pool of each group to become different so that it can be concluded that there is a new species formed. Gradualism is the concept that evolution occurs over a long period of time and that adaptive changes accumulated slowly and steadily over time in a population. Darwin believed in gradualism. Punctuated equilibrium states that speciation occurs quickly in rapid bursts, with long periods of stability in between.
Whether the rate of evolution occurs slowly over long periods of time or rapidly, the debate will continue as new evidence is compiled and alternative theories are brought to light. It is the nature of science to change as new evidence becomes available.
Ecosystem diversity includes the variety of habitats, living communities, and ecological processes in the living world.
Species diversity includes the vast number of different organisms on Earth. Genetic diversity refers to the sum total of all the different forms of genetic information carried by all living organisms on Earth. It gives rise to inheritable variation, which scientists believe provides the raw material for evolution.
For the Biology EOCT you should understand and explain the history of the evolutionary theory. Also review terms and
definitions that will help you in understanding this concept. A question may look like this:

Horses and tapirs have a common ancestor, but now look very different. Horses now are grassland animals adapted for grazing on grass and shrubs. Tapirs are jungle animals that live in dense forests and eat fruit, leaves, and aquatic
vegetation. Which of the following led to the development of such differences in the two species?
A selective breeding
B convergent evolution
C DNA hybridization
D natural selection

The correct answer is D. The animals with traits that contributed to success in a particular environment reproduced and passed on those traits. Horses and tapirs were not developed by selective breeding. DNA hybridization is a laboratory technique used to evaluate DNA similarities and differences. Convergent evolution is a process by which unrelated organisms develop similar attributes due to living in similar environments. You may also be asked to describe historical ideas that lead to modern thinking on
theories of origin. Remember that scientific theories are subject to change as new information becomes available. Keep in mind that technological advances are taking us places we have not been before. Marine biologists are discovering gigantic tubeworms
near the deep sea vents in the Marianas Trench. Paleontologists are uncovering fossils never before seen in Montana. It does not mean that these are newly-developed species. We just were not able to observe them before. Not everybody will agree with any one theory. Biologists turn to the fossil record. That is where we will look too!
??Explain How Fossil and Biochemical
Evidence Support the Theory??
Have you ever tried putting together a jigsaw puzzle but find that there are missing pieces and you just can’t quite get the picture together? That’s what faces biologists in trying to
put together the fossil record. The fossil record provides biologists with an incomplete picture of the evolution of the Earth’s plants and animals. Many fossils are the remains of
the hard parts of an organism after they have died. Many are from shells, bones or the remains of plants with thick cell walls. There are also impressions left behind in sediments along rivers and lakes. One problem with the fossil record is that there are no
remains of any “intermediate” or transition forms. That “missing link” is still missing. There are several reasons that paleontologists have for this theory. They estimate that
approximately two-thirds of all the organisms that ever lived were soft bodied. They didn’t have rigid skeletons or teeth that could be left behind. It also depended on where and how an organism died as to whether their remains could be fossilized. Fossils also could have been destroyed by erosion or pressure from overlaying rocks. Exposure to wind, rain, and soil erosion in certain landscapes could have prevented fossils from ever
forming. There are many environmental factors that must be taken into account when you look at the fossil record. One final problem is that of time-averaging. That is how paleontologists determine the length of time represented in a given fossil sample. They take into account the death, the burial, and any movement of the remains of the fossil. This makes it very difficult to determine when one organism lived relative to another.
When a scientist finds two different fossils in the same area (for example, a type of bone found among clamshells) it doesn’t necessarily mean that they lived in the same time period or even in the same area. Biologists have found a way to determine the relative ages of fossils within a semi-precise time limit. It is called radioisotope dating. These isotopes act as a clock for
measuring time. To use this method, scientists must know:
1 the half-life of the isotope being measured
2 how much of the isotope was originally present in the fossil or the rock containing the fossil
3 how much of the isotope is left
Carbon 14 (14C) is the primary isotope that is used in radioisotope dating. When an organism dies there is no additional carbon that is added to it. Scientists measure this carbon 14 to carbon 12, which is in living matter (that is, the ratio of 14C to 12C). This
ratio will change every year as the half-life of 14C decreases over time. The half-life of 14C is 5,770 years. That means that it takes 5,770 years for half of the carbon to become
stable, while the other half is still radioactive. One problem in this is that the half-life of carbon is relatively short compared to how old some scientists believe the Earth really is. So after about 50,000 years, the traceable amounts of carbon are gone. Scientists often use other isotopes such as uranium 235, which will decay into the daughter element, lead 207, in approximately 713 million years. So, biologists will utilize a number of ways to determine the age of fossils. They recognize distinct groups of fossils in specific rock layers. By matching rock layers
with fossils, geologists can determine the age of the rocks, while paleontologists can determine the age of the fossils. This is called relative dating. Once the ages have been established, they will use that information to build a phylogeny. A phylogeny is a description of the lines of descent of plants and animals as they lived from one era to the next. The most complete line that has been discovered is of the horse. Paleontologists have been able to trace similar forms of the horse and also show a sequence of changes that have taken place over a long period of time. But for most organisms, it’s not that easy. Fossil collections are not complete enough to determine any evolutionary patterns or traits. It makes it hard to determine on a phylogenic tree which
organism is descended from which. In this case, a biologist will infer likely phylogenies by comparing morphological features and chromosomal characteristics and insert the organism that is compatible. For the Biology EOCT, it is important that you are able to explain the concepts of how the fossil record and biochemical evidence support the theory of evolution. A question on the test may look like this:
Fossils of Archeopteryx show that this animal had feathers, like a bird. It also had a bony tail, teeth, and claws on its wings, like a reptile. This fossil is evidence that supports the idea that
A birds and reptiles have a common ancestor
B birds have changed very little over 150 million years
C reptile species are more advanced than bird species
D reptiles are warm-blooded like birds
The correct answer is A. The fossil is a transition fossil, showing the gradual loss of some unnecessary physical structures and the gradual development of those characteristics that were beneficial to survival. Most birds are very different from the fossil Archeopteryx and have changed a great deal in the past 150 million years. There is no evidence in this fossil to show that reptiles are more advanced than birds. Reptiles are not warm-blooded like birds.
Extinction
Extinction is the permanent loss of a species. We know that extinctions have occurred over time. The great red elk and the saber tooth tiger are two examples of extinct species.
Scientists can only speculate about the forces that have driven certain species and even whole lineages of organisms to become extinct. Paleontologists have come to the conclusion that there have been five mass extinctions, resulting in a great number of
species being completely wiped out. They believe one of these mass extinctions to have occurred at the end of the Permian period, when 96% of marine invertebrates became extinct. The other one they believe to have occurred is at the end of the Cretaceous period, when they believe 60-75% of marine species died. What would cause such a catastrophic event that would lead to this extinction? Researchers must take caution in interpreting data on these mass extinctions. We have learned that the fossil record is not a complete way to determine all the species that once lived. There are missing pieces to the puzzle. Where are these missing pieces, and did they ever exist? Also, if there were catastrophic events that were the cause of these extinctions, did they happen quickly or did they occur over a long period of time? If they occurred over a long period of time, why did the species not adapt to their changing environment in order to survive? Questions like these spark an interest and inspire people
like Darwin, Wallace, Lamarck, and others to search the world around us to understand where life began.
??Relate Natural Selection to Changes in Organisms??
Remember that the key to Darwin’s theory of organisms struggling for existence came from the concept that some organisms have an advantage over others. This advantage
increases the organism’s survival rate. If the physical appearance (phenotype) of an organism changes to improve the reproductive success of the organism, then it makes sense that the genes involved have also changed. Well, let’s take a look. If you look around your classroom, you notice a great variety of sizes, shapes, and colors among your classmates. The same is true for just about every species. Within each species is a vast array of morphological (structural) differences. This presents a problem for evolutionary biologists. It is impossible to determine the exact number of gene loci and alleles that are responsible for variation. Remember that one gene can affect a number of traits and, conversely, two or more genes can affect one single trait. Is there an easy genetic explanation? Mendel was on the right track in working with genes that controlled physical traits. It was in the 1950s and ’60s that new techniques allowed molecular biologists to discover the genetic code and protein structure. This enabled them to explore genotypes and phenotypes at a deeper level,
making the connection between genetics and adaptation by the process of natural selection.
Natural selection acts on an organism’s phenotype and indirectly on its genotype. Gene pools change over time due to nonrandom mating, genetic drift, mutation, migration and natural selection. Natural selection is credited with the vast number of adaptations that allow populations to survive in their environments.
Fitness
Geneticists define the term fitness as the relative reproductive efficiency of various individuals or genotypes in a population. What does this mean? The fitness of an individual depends on the probability that the one individual will contribute its genetic
information to the next generation. It depends on that organism’s ability to survive and reproduce successfully. It is not necessarily the strongest, biggest, or most aggressive animal that has the highest fitness rating. It is a combination of structure, physiology, biochemistry, and behavior that determines an animal’s fitness. When an organism has a set of alleles and proteins with a variety of phenotypes and biological capabilities, it enables the individual to survive under a wide range of environmental factors.  Biologists use two rules to tie together geography with fitness of allelic variations in warm-blooded animals. Environment plays an important role in determining which of several alleles is optimum for a population’s survival. Selective processes will lead to an increase in adaptations of populations in their environment. Let’s look at some types of selective processes in natural selection. Keep in mind that natural selection doesn’t always increase the complexity of an organism’s structures or behaviors. Also, natural selection doesn’t produce new genotypes and phenotypes, but it rather eliminates the less fit, enabling the
more fit to reproduce and ensuring the species survival.
Stabilizing Selection
Stabilizing selection, also called normalizing selection, is responsible for maintaining the status quo for an organism’s genetic makeup in an environment. It is common in environments that have remained stable over long periods of time. Possibly, the
phenotype has not changed much because it has become very well adapted to its environment, such as the open sea or the high-pressured regions of the sea floor.
Directional Selection
Directional selection involves change from one phenotypic property to a new one. When environmental conditions favor the survival of individuals carrying a genetic variant, the outcome is an increase in the frequency of that variant in the population.
Directional doesn’t mean that something is directing change. It may be that the variant arose by chance or was already part of the allele, and selective pressure opted for the preservation of it. Many insects have become resistant to pesticides. Those with enzymes that resist the organophosphate insecticides sprayed on them survive and reproduce, passing on the genes for the enzyme.
Diversifying Selection
When a population is faced with conditions so diverse that no single phenotype is more successful that any other, genetic and phenotypic variability allow different selective pressures to operate at the same time. This results in two or more phenotypes, each adapted to some specialized feature for a particular part of the total environment. Some plants may be highly specialized for a certain environment and will not grow in any other place.
Disruptive Selection
Disruptive selection results in the disappearance of forms that are considered intermediate between several extreme variants that are more adapted to the new environment. Disruptive selection will split a species into two or more groups by strongly
selecting against the intermediate or average phenotypes.



Balancing Selection
Balancing selection operates to counteract the loss of variant alleles in a population. There are two forms of balancing selection: heterozygote advantage and frequency-dependent selection. Heterozygote advantage exists when a heterozygote (Aa) has a higher fitness than either homozygote (AA, aa).
Heterozygote advantage is used by plant and animal breeders by breeding together two distinct parental lines in order to improve their product; a sweeter ear of corn or a line of prize dogs. There is a disadvantage to this. It is called genetic load. Genetic load is
the sum total of those alleles that yield some advantage when they are heterozygous but that are lethal or deleterious when homozygous. Frequency-dependent selection is a process that operates when the relative fitness of the genotypes in a population vary according to their frequency. It occurs when a
predator concentrates on a particular phenotype, usually the most common and the most abundant. Natural selection can take on many forms and produce diverse effects on organisms. In
summary, natural selection may maintain the status quo for a population in its genotype or in its phenotype. Trends may occur in different directions; decreasing a species or increasing a species. Increasing the diversity in genotype and phenotype may result in a new species. Whatever job natural selection takes on, it is evident to most biologists that it is the major driving force in the evolution of life. A lot of material has been covered. On the Biology EOCT, you may be asked to describe the different variations of natural selection and their impact on a species. A question may look like this:
Although the Arctic fox and the kit fox are closely related, they look very
different because the individuals
A acquired traits during their lifetimes that contributed to survival
B with traits most suited to their environments reproduced most successfully
C migrated long distances to environments that most suited their traits
D passed on to their offspring acquired behaviors that were helpful
The correct answer is B. The animals gradually evolved to have very different traits that helped them succeed in very different environments. Traits and behaviors acquired by an animal during its lifetime are not passed on to the next generation. The animals also would not have moved to a dramatically different region to try to fit their traits to their environment.
Spotlight on the Standard
??Recognize the Role of Evolution to Biological Resistance??
New techniques in molecular biology have given researchers new insight into genetic mechanisms that may be involved in some types of directional selection. Remember that directional selection involves change from one phenotypic property to a new one. It refers to a trend that happens consistently over time. When a bed of oysters in Malpeque Bay was infected with a lethal pathogen in 1915, it almost wiped out the oyster industry. But
10 years later, the oysters were making a comeback. By 1940, the Malpeque Bay was producing more oysters than it ever had. They began to repopulate other areas that had been wiped out. What brought about this drastic change for the oyster? Directional
selection. Out of the 50 million or so offspring that were produced each year by the oysters, a fraction of those offspring carried an allele that was resistant to this pathogen. So when the environmental conditions were favorable for the offspring that carried this allele, the outcome was an increase in that variant in the population. This resulted in an increase in healthy oysters.
Many insects have developed a resistance to insecticides. Simple point mutations may be the process by which enzymes like acetylcholinesterase are modified so they are no longer susceptible to the insecticide. Some mosquito populations react differently when exposed to organophosphates. They have a gene coding for a detoxifying esterase enzyme. It keeps the organophosphate at a nonpoisonous level. It has been discovered
that in a swamp treated with a pesticide, the surviving mosquitoes had an amplification of this gene. Over 250 copies were present in each diploid cell. With this large number, the mosquitoes can make large amounts of the esterase enzyme resulting in detoxifying the insecticide. This gene amplification has been observed in other arthropods, in mammalian tumor cells, and during cell differentiation. Biologists are not sure what exactly triggers or signals this process but they do know that once it starts, gene amplification takes on specific characteristics that enable it to perform its particular function. Viruses are
another organism that are constantly evolving in response to changes in their environment. Some don’t change quickly, like smallpox or measles. This gave biologists time to create a vaccine against them. Others change very quickly, like the flu. The flu
virus mutates rapidly, constantly changing its genotype and phenotype, so the flu virus changes year to year. The body does not recognize the new virus as anything harmful, so it doesn’t send out anything to attack it. Another adaptation of viruses is that certain viruses can live in two or more different hosts. One virus may originally live in pigs and geese and then move on to live in humans and ducks. Viruses carry their genetic information on eight pieces of DNA. So if two strains of the virus infect the same cell, some of those genes will get mixed up, resulting in a new strain of the virus. This can cause major problems for the host.  It is very important to review your textbook and study these concepts. On the Biology EOCT you may be asked to explain the importance of evolutionary changes on organisms that are affected by biological resistance and how these come about. A question may look like this:
Some viral diseases require only one vaccination, which lasts for years. For other
diseases like the flu, vaccinations last only one season. The flu vaccine lasts such a
short time because the flu virus
A is more easily transmitted
B mutates much more rapidly
C is less dangerous
D is much smaller
The correct answer is B, the flu virus mutates much more rapidly.
Sample Questions for Content Domain V
This section has some sample questions for you to try. After you have answered all of the questions, check your answers in the “Answers to the Content Domain V Sample Questions” section that follows. This section will give you the correct answer to each
question, and it will explain why the other answer choices are incorrect.
1 From the following answers, which is considered by most biologists to be the most accurate in supporting the theory of evolution?
A fossils
B embryology
C DNA sequencing
D genetic equilibrium
2 The development of radiocarbon dating allows scientists to see how many times carbon atoms have been through half-lives. Since scientists know the length of a C-14 half-life, they can gain knowledge about fossils using the C-14 dating technique. When radiocarbon dating was first introduced, it changed the way people thought about how organisms evolved because the technique showed
A how long ago some organisms were alive
B that eating habits have changed in some animals
C how different the chemical composition was long ago
D that most plants were gymnosperms
3 There are millions of species of organisms living at this time and new species are still being discovered. Based on Darwin’s
theory of evolution, which of the following best describes how
millions of species have developed?
A Organisms passed on acquired characteristics to evolve from
lower life forms to higher life forms.
B Organisms were selectively bred to create different species.
C Completely different species crossed with one another to form
the many different organisms.
D Different genetic variations in organisms were selected in
different environments.
4 Which of the following best supports the idea that organisms and environments have changed over time?
A the discovery of fossilized fern plants in Antarctica
B the production of sterile hybrid animals such as the mule
C the many different species of plants in tropical areas
D the ability of many animals to learn new behaviors rights reserved.
5 The cotton whitefly has become a key pest, damaging many kinds of crops. The cotton whitefly has developed resistance to a variety of pesticides. Pesticide resistance would most likely develop in insects that
A reproduce rapidly
B feed on few types of plants
C undergo complete metamorphosis
D live in very limited regions
6 The DNA of an organism contains information that is used to sequence amino acids to form specific proteins. The existence of different organisms with very similar amino acid sequences is evidence of
A a common ancestor
B common adaptive behaviors
C a similar diet
D a similar environment
7 Microorganisms such as bacteria are able to change and adapt much more quickly than other organisms. Bacterial populations,  for example, are able to build a resistance to antibiotics within months, whereas compounds that
are toxic to animals remain toxic to animals for many years. One reason for their rapid adaptability is that microorganisms
A are highly motile
B have a short life span
C have specialized organelles
D are chemosynthetic
Answers to the Content Domain V Sample Questions
1. Answer: C Standard SB5.d: Relate natural selection to changes in organisms The correct answer is C. DNA is the most accurate tool for determining relatedness among individuals. Remember that when Darwin developed his theory of natural selection, he did so without the benefit of the knowledge of genes. We have learned that adaptations of species are determined by the genes encoded in the DNA. Fossils are a way to determine the evolutionary process, but it is not the best way. There are a lot of missing puzzle pieces that are not accounted for. Genetic equilibrium is when there is no change in the frequency of alleles within a population. It is believed that when a population is in genetic equilibrium, it is not evolving.
2. Answer: A Standard SB5.c; Explain how fossil and biochemical evidence support the theory
The correct answer is A. Using the half-life value of carbon and knowing how many half-lives the carbon had experienced allowed scientists to calculate estimates of how long the organisms were alive. In many cases the time frame was much larger than
originally thought. Radiocarbon dating offers no information about eating habits or chemical composition (other than carbon). C-14 dating did not provide information about the reproductive strategies of organisms.
3. Answer: D Standard SB5.d Relate natural selection to changes in organisms The correct answer is D. As organisms reproduced, different combinations of traits and genetic mutations produced organisms with different characteristics. Organisms with
different traits were successful in different environments. Many species evolved to fit the many different niches in the different environments. Characteristics acquired during an organism’s life are not passed on to future generations. Selective breeding by humans did not take place until long after millions of different species already existed. Organisms of completely different species rarely cross successfully because of incompatibility of their DNA.
4. Answer: A Standard SB5.a Trace the history of the theory
The correct answer is A. The existence of fossilized ferns in Antarctica is evidence that the environment of Antarctica has changed greatly. The organisms that live in Antarctica now are adapted for a very different climate than the fossilized ferns that once lived there. The breeding of sterile hybrid animals such as the mule would not contribute to the change of organisms over time because the hybrids would not be able to reproduce to
pass on their unique combination of traits. The existence of many species of tropical plants does not show that the plants have changed over time. Learned behaviors are not passed on to future generations.
5. Answer: A Standard SB5.e Recognize the role of evolution to biological resistance The correct answer is A. Organisms that reproduce rapidly can fix new traits quickly because there are many generations in a short time period and mutations that help the organism survive are passed on to many more organisms in a short time. Usually, living in a limited region or eating only a few types of plant does not help organisms develop resistance because if there are significant environmental changes, these organisms are more likely to be reduced in numbers because they are not very adaptable. The process of metamorphosis does not help organisms develop pesticide resistance.
6. Answer: A Standard SB5.c Explain how fossil and biochemical evidence support the theory The correct answer is A. Organisms with similar amino acid sequences are related to a common ancestor and will have similarities in their DNA. Many organisms have a similar body structure due to their environment or diet, but are not related (seals and penguins).
7. Answer: B Standard SB5.e Recognize the role of evolution to biological resistance The correct answer is B. The ability to build a resistance to antibiotics is a result of the fact that many types of bacteria are able to produce thousands of generations in the same population in a matter of days. Not all bacteria are highly motile and this trait does not help the bacteria develop resistance. Chemosynthesis and specialized organelles do not
contribute to the development of antibiotic resistance. Antibiotic resistance is a result of natural selection.
LABORATORY SAFETY
• Conduct and Preparation in the Laboratory
• Eye Safety
• Safety Equipment
• Dress Code and Neatness
• Working with Sharp Instruments
• Working with Chemicals
• Working with Glassware
• First Aid and Handling Emergencies
• Waste Disposal and Cleanup
Co-requisite Domain: Characteristics (and Nature) of Science
This part of the domain will test how well you understand the importance of ethics in science. Scientists should be curious, honest, open, and skeptical in the pursuit of knowledge. You should develop these traits during your own activities in the lab and classroom. In the lab, you might have noticed that different explanations can often be given for the same evidence. The four qualities, just mentioned, should lead you and others to find the most accurate explanation for the evidence. This requires further understanding of the scientific problem. It will require you to design and perform new experiments. These experiments will either support or weaken the opposing explanations. Before starting the experiments, you and your classmates should use standard safety practices. These should be carefully followed in the classroom, laboratory and out in the field. These practices include:
• Always use correct procedures when working with scientific apparatus
• Always use proper techniques in the laboratory
• Immediately identify and report safety problems and violations
A LOOK THE CO-REQUISITE DOMAIN
Test questions in this content domain will measure your
ability to use scientific processes and solve problems. Your
answers to the questions will help show how well you:
?? Identify tools, terms and processes used in scientific
inquiry, including laboratory safety and scientific
research.
?? Comprehend how scientific knowledge is developed.
?? Recognize how scientific information is properly verified
and communicated.



Below is an example of a question on safety practices.
A student plans an experiment to separate a water solution containing borax by heating the solution over a Bunsen burner. In this way, the water is evaporated. Which piece of safety clothing or equipment is MOST appropriate for this
experiment?
A cotton gloves
B dust mask
C fume hood
D safety goggles
Safety goggles (eye protection) should be worn when an experiment involves heating chemicals, so D is the correct answer. Since water is the substance being evaporated and
borax is a dissolved solid, a fume hood is not necessary, so C is incorrect. Choices A and B do not represent equipment that is needed for this experiment. By this time, you should have addressed all safety issues. Now you are ready to identify
and investigate a scientific problem. First, reasonable hypotheses should be suggested for an identified problem. Then procedures should be developed to solve the problem. These procedures, when carried out, will require you and your lab group to gather, organize and record data. At the end of the experiment, the data points should be graphed so you can compare and analyze your results. Statistics should be summarized as well. Based on this
work you should develop reasonable conclusions based on the data. You will evaluate whether your conclusions are reasonable by reviewing the process and checking your data against all other available information. You will find that good data collection and organization are vital for success. As a result, you should learn to use tools and instruments for observing and measuring data. As part of this process, you should do the following:
• Develop and use orderly procedures for recording and organizing information.
• Use technology to produce tables and graphs
• Use technology to develop, test, and revise your experimental or mathematical
models
STRATEGY BOX—Graphs
When working with graphs, carefully read the title and the label on each axis. Check for any other information that might be included in the graph. When you think you have the answer, double check the information given in the graph.
On the test, you will need computation and estimation skills to analyze data and create scientific explanations. Sometimes you will notice large differences between your estimates and your calculated answers. Measurement errors may have a noticeable effect on calculations. Good computation and estimation skills are needed to produce reliable results. You should know that accuracy indicates how close your measurements approach the accepted value. Precision is the agreement between two or more measurements. You should be able to express the correct number of significant figures in your calculations. Scientific notation should be used to report very large or very small values. Finally, you should be able to solve problems by substituting values into simple algebraic formulas. You might also use dimensional analysis. Below is an example of a question that assesses your computational skills in a lab activity. In a field investigation, students predicted the population density of birch trees in a
temperate forest. Three groups of students gathered data by counting the number of birch trees in a 1- m2 area. They recorded their data in the table below. Based on the data above, what is the average number of trees that live in a 400 m2
section of the same habitat, and what is the average diameter of the trunk of each tree?
A 2800 trees with an average trunk diameter of 9 cm
B 21 trees with an average trunk diameter of 9 cm
C 21 trees with an average trunk diameter of 27 cm
D 280 trees with an average trunk diameter of 27 cm
Number of Trees 11 3 7
Average diameter of trunk of the birch trees in centimeters
5 14 8
INVESTIGATING LIKE A SCIENTIST
• State the problem – ask a question
• Do background research – gather information
• Form a hypothesis – suggest an answer
• Design an investigation – perform an experiment to test the answer
• Collect data – record the results of the experiment; make a data table if necessary
• Analyze data – interpret the results of the experiment
• Draw conclusions – explain your results
• Identify new questions raised by the conclusions for further investigation
• Communicate results – share your results The correct answer is A. The average number of trees per square meter was multiplied by 400. The average of the measurements for trunk diameter is correctly determined. Option B and Option C are wrong because the trees for the three plots were added. Option C is also wrong because the trunk size was not averaged. Option D is wrong because the trunk diameter was not averaged.
One of the goals of scientists is to communicate scientific investigations and information clearly. With this in mind, you should be able to write clear, logical laboratory reports.
You should also be able to write clear, understandable critiques of current scientific issues, including possible alternative interpretations of scientific data. When presenting
data, you should use it to support scientific arguments and claims during a group discussion.
To understand how science leads to new discoveries, you should be able to analyze how scientific knowledge is developed. In order for science to grow and develop, certain assumptions are required. First, scientists assume that the universe is a vast single system in which basic principles are the same everywhere.
These universal principles are discovered through observation and
experimental confirmation. Science is not exact or perfect. From time to time, scientific explanations may change as new data result in changes in the scientific view of how the world works. Most of the time, small changes to previous models lead to
shifts in scientific knowledge. Major changes in scientific views typically occur when a new phenomenon is observed. These changes also occur when an individual or research group gives an insightful interpretation of existing data. Hypotheses often cause scientists to develop new experiments. These experiments
produce additional data. The results of these experiments are tested and revised. New and old theories may occasionally be rejected. The process of testing and fine-tuning theories
never ends as scientists try to gain new insights into old problems. A question on the test might look something like this:
The development of a useable scientific model may be hindered by errors and mistaken beliefs. The scientific method, however, should eventually lead to better
scientific models because
A contemporary scientists appreciate the scientific method more than ever.
B new computer technology  immediately detects the scientists’ errors.
C more complex scientific models lower the probability of inaccurate results.
D additional scientific research either confirms or replaces flawed theories.
Answer D is the correct answer. Continuing research leads to better explanations of phenomena. This leads to the revision or rejection of present-day theories.
Answer A is incorrect because it is incorrect to assume that scientists today appreciate the scientific method more than previous scientists did. Computers do not eliminate human error so answer B is incorrect. Just because a model is more complex, it does not lessen the likelihood of inaccurate results; it could make inaccurate results more likely. Answer C is therefore incorrect. Finally, you should understand the important characteristics of the process of scientific inquiry. These characteristics include the following: • The conditions of the experiment should be controlled to obtain valuable data,
• The quality of data, including possible sources of bias in hypotheses, observations, data analyses, and interpretations, should be critically examined and tested. • Peer review and publication should be employed to increase the reliability of
scientific activity and reporting. • It should be remembered that the merit of a new theory is judged by how well scientific data are explained by the new theory. • The ultimate goal of science should be to develop an understanding of the natural
universe which is free of human bias. • It should be remembered that scientific disciplines and traditions differ from one
another. These differences include what is being studied, the techniques used, and the outcomes being sought. If you develop a good understanding of all the concepts presented here, then you will be successful answering the questions in this co-requisite domain.

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