Answer Key—Tests

Chapter 1—Test A

Multiple Choice 1. b 2. d 3. b 4. c 5. b 6. b 7. c 8. d 9. b 10. b 11. b 12. a 13. c 14. d 15. b Completion 16. controlled 17. open-minded; skeptical; objective 18. peer review 19. function 20. 3 Short Answer 21. Sample answer: Reviewers must be anonymous and independent so that they are not biased or influenced by the ideas in the papers or the scientists who wrote the papers. 22. Saying “just a theory” implies that the idea is just a hunch. Scientific theories like evolution are much stronger than a hunch—they are well– tested and well–accepted explanations supported by a large body of evidence. 23. A bias is a particular preference or point of view that is personal rather than scientific. 24. Student answers may include any science-based question that affects society but is not a question that involves morals, ethics, or making judgements based on personal opinion. Using Science Skills 25. Reproduction is important to maintaining a group of animals. An individual member of the group can survive without reproduction, but the entire group would die out if none of its members reproduced. 26. Rabbit B is the control. 27. Ice (temperature) is the variable. 28. The fur color of the Himalayan rabbit changes with the temperature. 29. Rabbit B is the control. Without a control, the cause of any observed change cannot be determined. 30. When the body of a Himalayan rabbit is cool, the rabbit’s fur will grow in dark. When the rabbit’s body is warm, the fur will grow in white. Essay 31. One goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions. 32. A theory can change over time. No theory is considered absolute truth. As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation. 33. Anything lacking one or more of the following characteristics of life is nonliving: made up of cells; reproduces; based on a universal genetic code; grows and develops; obtains and uses materials and energy; responds to its environment; maintains a stable internal environment; and, taken as a group, changes over time. 34. The functions of the structures are different. The bird wing and the bat wing allow those animals to fly and the


flipper helps the whale swim through water. The human arm has many functions including grasping things, moving objects, and helping move the human body around. The structures have similar bone arrangements and are located at approximately the same place on each organism’s body. However, the structures are not completely identical. For example, bone lengths are different and joints are located in different places. 35. A population is a group of one type of organisms that live in an area. Examples might include a herd of bison on a prairie; all of the clover plants in a field; all of the aphids on a plant; all of the earthworms in a particular plot of ground. Accept any two answers that correctly identify a population with one type of organism in one location.

Chapter 1 —Test B

Multiple Choice 1. b 2. b 3. d 4. b 5. c 6. c 7. c 8. a 9. b 10. b 11. a 12. d 13. b 14. c 15. d Completion 16. predictions 17. curiosity 18. theory 19. metabolism 20. energy Short Answer 21. Science is always changing and advancing so the facts may change over time. 22. Sample answer: The missing mineral in the diet is needed for the health of the rats. 23. Sample answer: The paper may contain mistakes, unfair influences, or fraud. 24. Saying that an idea is “just a theory” implies that the idea is just a hunch. Scientific theories like evolution are much stronger than a hunch—they are well-tested and well-accepted explanations supported by a large body of evidence. 25. Global ecologists study how humans impact the Earth and the other living things on Earth. Using Science Skills 26. meter, centimeter, millimeter, kilometer 27. Milliliters and cubic centimeter are equal units. 1000 mL = 1 L = 1000 cm3. 28. The boiling point of water in degrees Celsius is 100°C. 29. The prefix kilo- means 1000. 30. 2 L of water is equal to 2000 mL.

Chapter 2 —Test A

Multiple Choice 1. c 2. b 3. d 4. b 5. d 6. b 7. a 8. c 9. a 10. b 11. d 12. c 13. a 14. d 15. b Completion 16. electrons 17. electrons 18. monomers 19. reactants Short Answer 20. activation energy 21. No. The properties of a compound are usually

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Answer Key—Tests • Chapter 2

different from the properties of the elements that make up the compound. 22. The sodium atom loses an electron and becomes positively charged. The chlorine atom gains an electron and becomes negatively charged. The two charged ions then form an ionic bond. 23. The atoms in H2 gas and O2 gas are rearranged into water molecules. Covalent bonds are formed between the H and O atoms. 24. The ability of water to form multiple hydrogen bonds accounts for water’s properties of adhesion and cohesion. 25. A mixture is a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. Using Science Skills 26. enzyme Y 27. about 45°C 28. Enzyme X’s optimum temperature is 40ºC and enzyme Y’s optimum temperature is about 80ºC. 29. enzyme X 30. enzyme Y Essay 31. Isotopes of an element have the same number of protons but different numbers of neutrons. Because the mass number is the sum of the atomic number (number of protons) and the number of neutrons, isotopes of the same element have different mass numbers. 32. The pH of pure water is 7, or neutral. Tomato juice, with a pH of 4, contains higher concentrations of H+ ions than pure water and is an acidic solution. Soap, with a pH of 10, contains lower concentrations of H+ ions than pure water and is a basic solution. 33. First, organic compounds contain carbon atoms, each of which has four valence electrons. Each electron can join with an electron from another atom to form a covalent bond. Carbon can bond with many elements, including hydrogen, oxygen, phosphorus, and nitrogen. Second, a carbon atom can bond to other carbon atoms, which gives carbon the ability to form chains that are of great length. These carbon–carbon bonds can be single, double, or triple bonds. Chains of carbon atoms can even close upon themselves to form rings and loops. Carbon thus has the ability to form millions of different large and complex structures. 34. Carbohydrates, nucleic acids, and proteins are polymers because each is made up of different monomers. Simple sugars (monosaccharides), nucleotides, and amino acids are the monomers that make up those polymers. Some lipids are made up of a glycerol molecule and three fatty acids. These are not polymers because they are not made up of monomers. 35. During a chemical reaction, chemical bonds in the reactants are broken and chemical bonds are formed to make the products. Energy is released or absorbed whenever bonds are broken or formed.

Chapter 2 —Test B

Multiple Choice 1. d 2. b 3. c 4. a 5. b 6. a 7. d 8. b 9. a 10. c 11. a 12. b 13. c 14. b 15. d Modified True/False 16. T 17. T 18. T Completion 19. chemical Short Answer 20. ionic 21. The sodium atom loses an electron and becomes positively charged. The chlorine atom gains that electron and becomes negatively charged. The two charged ions then form an ionic bond. 22. Add some salt—the solute—to a container of water—the solvent—to produce a salt solution. 23. Atoms have equal numbers of negative electrons and positive protons. 24. The energy comes from chemical reactions that release energy stored in food. 25. Answer should include two of the following: regulating chemical pathways, making materials that cells need, releasing energy, and transferring information. Using Science Skills 26. hydrochloric acid 27. 6.2 28. 13.0 29. The H+ ion concentration of sea water is lower than the H+ ion concentration of pure water. 30. Yes. According to Figure 2–2, some foods such as tomatoes are acidic, yet are safe to eat.

Unit 1 —Test A

Multiple Choice 1. c 2. b 3. c 4. a 5. d 6. a 7. b 8. a 9. a 10. c 11. b 12. b 13. d 14. b 15. c Completion 16. independent or manipulated 17. compound 18. enzyme 19. hypothesis 20. asexual Short Answer 21. Students should list five of these eight characteristics: made up of units called cells, ability to reproduce, based on a universal genetic code, ability to grow and develop, ability to obtain and use materials and energy, ability to respond to the environment, ability to maintain a stable internal environment, and tendency as a group to change over time. 22. Isotopes of an element all have the same chemical properties because they have the same number of electrons. 23. An acidic solution contains a higher concentration of H+ ions than pure water and has a pH value above 7. A basic solution contains a lower concentration of H+ ions than pure water and has a pH value above 7. 24. A chemical reaction is a process that changes one set of chemicals into another set of chemicals. 25. Cell cultures can be used to test cell responses under controlled conditions, to study interactions between cells, and to select specific cells for further study.

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Answer Key—Tests • Chapter 3

26. Adhesion is the attraction between molecules of different substances, whereas cohesion is the attraction between molecules of the same substance. 27. Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. Using Science Skills 28. milligram, gram, kilogram, metric ton 29. 0°C 30. one hundredth 31. 5000 32. Because metric units are scaled on multiples of 10, converting meters to centimeters entails multiplying by 1000, a multiple of 10. Converting yards to inches, however, would entail multiplying the number of yards by 36, which is the number of inches in each yard. Essay 33. A hypothesis is a proposed scientific explanation for a set of observations. A particular hypothesis may become so well supported that scientists consider it a theory. A theory applies to a well-tested explanation that unifies a broad range of observations. 34. An ionic bond is formed when one or more electrons are transferred from one atom to another. A covalent bond forms when electrons are shared between atoms. 35. In an enzyme-catalyzed reaction, the substrates bind to the site on the enzyme called the active site. The active site and the substrates have complementary shapes. The enzyme and the substrates form an enzyme-substrate complex, and they remain bound until the reaction is done.

Unit 1 —Test B

Multiple Choice 1. b 2. b 3. c 4. a 5. c 6. d 7. a 8. d 9. c 10. c 11. b 12. a 13. d 14. b 15. d Completion 16. sexual 17. enzyme 18. asexual 19. protons 20. carbohydrates Short Answer 21. An acidic solution contains a higher concentration of H+ ions than pure water and has a pH value above 7. A basic solution contains a lower concentration of H+ ions than pure water and has a pH value above 7. 22. A chemical reaction is a process that changes one set of chemicals into another set of chemicals. 23. Adhesion is the attraction between molecules of different substances, whereas cohesion is the attraction between molecules of the same substance. 24. In a saltwater solution, the sodium and chloride ions that make up the salt gradually become dispersed in the water, becoming evenly distributed throughout the solution. 25. An enzyme speeds up a chemical reaction by lowering the activation energy. Using Science Skills 26. coffee 27. 12.0 28. Blood is a base. 29. Lemon juice has more H+ ions than OH– ions. 30. 200 times

Chapter 3—Test A

Multiple Choice 1. c 2. b 3. c 4. a 5. c 6. d 7. d 8. b 9. c 10. d 11. d 12. b 13. a 14. a 15. d Modified True/False 16. F; oxygen 17. T 18. T 19. T Completion 20. decomposers 21. 50 22. biotic Short Answer 23. Organisms interact with each other and their environments. These interactions produce a web of interdependence among individual organisms, species, populations, communities, and the environments in which they live at every level of organization in the biosphere. 24. The two producers are alike because they both produce carbohydrates and oxygen and are essential to the flow of energy through the biosphere. They are different because they get their energy from different sources. 25. Sometimes consumers are much less massive than the organisms they feed upon. For example, thousands of insects may graze on a single tree. The tree has a lot of biomass, but it is only one organism. So the “base” of the pyramid will be small and the next level up will be wider. Using Science Skills 26. Figure 3–8 is an example of a model. 27. The deer is on the second trophic level, so it is two steps away from the sun. You can tell because there is only one arrow between it and a producer that relies on the sun. 28. An ecosystem is a collection of all the organisms that live in a particular place, together with their nonliving, or physical, environment. A food web shows only the living parts of an ecosystem. It does not show the nonliving parts of the ecosystem. 29. There is one first-level consumer for corn, three for carrots, four for flowering shrubs, and one for trees. 30. The mouse population would be the most directly affected. The mice are the only consumers who eat corn. Essay 31. Ecologists use observation, experimentation, and modeling. Observation involves asking questions and using senses to gather information. Experimentation is used to test hypotheses. Ecologists might set up artificial environments or carefully change parts of natural ecosystems to do experiments. Ecologists use modeling to understand phenomena that are difficult to study directly. Some models are mathematical models based on data gathered through observation and experimentation. 32. Students’ answers will vary. All answers should describe at least one biotic factor affecting more than one abiotic factor. Sample answer: Trees around a pond can shade the pond, thereby reducing the amount of sunlight