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OpenStax
Biology 2e –
Instructor
Answer Guide
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Unit 1: The Chemistry of Life
Chapter 1: The Study of Life
Visual Connection Questions
1. Apply the scientific method to a toaster problem:
● Observation: My toaster doesn’t toast my bread.
● Question: Why doesn’t my toaster work?
● Hypothesis: There is something wrong with the electrical outlet.
● Prediction: If something is wrong with the outlet, my coffeemaker also won’t work when plugged into
it.
● Experiment: Plug the coffeemaker into the outlet.
● Result: Coffeemaker works.
Conclusion: The hypothesis is incorrect.
Alternative hypotheses: The toaster might be broken or was not turned on.
2. Inductive or deductive reasoning:
1. Inductive
2. Deductive
3. Deductive
4. Inductive
3. False statement:
● b. Communities exist within populations which exist within ecosystems. (Correct hierarchy
is population → community → ecosystem)
Review Questions
4. First forms of life: microorganisms
5. Suggested, testable explanation: hypothesis
6. Not a natural science: computer science
7. Logical thinking from observations to conclusion: inductive reasoning
8. Process ensuring research is original and significant: peer review
9. Plants grow faster with music example: inductive reasoning
10. Smallest unit of life: cell
11. Why viruses aren’t living: not made of cells
12. Membrane-enclosed nucleus characteristic: eukaryotic cells
13. Group of same-species individuals: population
14. Hierarchy of biological organization (largest → smallest): biosphere, ecosystem, community,
population, organism
15. Most recently evolved organism in phylogenetic tree: branch tips
Critical Thinking Questions
16. Scientific method applied to everyday life:
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● Example: Car won’t start → hypothesis: dead battery → experiment: replace or charge battery → check if
car starts.
17. Applied science example: Vaccines preventing diseases like polio, measles, and influenza.
18. Topics inside biology: disease mechanisms, plant responses, environmental impact on species
Topics outside biology: rock formation, planetary orbits
19. Cancer example:
● Basic science: What evolutionary purpose might cancer serve?
● Applied science: What interventions prevent cancer at the cellular level?
20. Two criteria for life and nonliving examples:
● Criteria: organization and regulation
● Nonliving examples: sedimentary rocks, technology
21. Levels of organization (smallest → largest):
Hydrogen atom → water molecule → skin cell → liver → elephant → wolf pack → tropical rainforest →
planet Earth
22. Homeostasis example: Sweating cools body; thirst triggers water intake to maintain hydration.
23. Microscopic to global study:
● Cell → tissue → organ → organism → population → community → ecosystem → biosphere
Chapter 2: The Chemical Foundation of Life
Visual Connection Questions
1. Neutrons in carbon isotopes:
● Carbon-12 → 6 neutrons
● Carbon-13 → 7 neutrons
2. Electron gain/loss for stable configuration:
● Group 1 → lose 1 electron
● Group 14 → gain 4 electrons
● Group 17 → gain 1 electron
3. False statement about enantiomers:
● Must have at least three different groups connected to central carbon (should be four)
Review Questions
4. Xenon neutrons: 108 − 54 = 54
5. Atoms differing in neutron number: isotopes
6. Potassium electron configuration: shells 1–3 full, shell 4 has 1 electron
7. Weak chemical bond: hydrogen bond
8. False statement: water is the most abundant molecule in the atmosphere
9. Acids added → pH decreases
10. Molecule binding H⁺ → base
11. True: acids and bases neutralize each other
12. Carbon can bond with 4 other atoms
13. Not a functional group: sodium
Critical Thinking Questions
14. Ionic vs covalent bonds:
● Ionic: electron transfer, moderate strength
● Covalent: electron sharing, stronger
15. Importance of hydrogen bonds/van der Waals:
● Maintain structure of proteins and DNA for proper function
16. Buffer function:
● Absorb H⁺ or OH⁻, prevent pH swings (e.g., bicarbonate system)
17. Insects walking on water:
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● Surface tension due to cohesion between water molecules
18. Carbon’s importance:
● Forms up to 4 covalent bonds, allows large, complex molecules
19. Saturated vs unsaturated triglycerides:
● Saturated: no double bonds, solid
● Unsaturated: ≥1 double bond, liquid
Chapter 3: Biological Macromolecules
Visual Connection Questions
1. Sugar types:
● Glucose, galactose → aldose
● Fructose → ketose
2. Amino acid distribution:
● Soluble proteins → polar/charged outside, nonpolar inside
● Membrane proteins → nonpolar with lipid tails, polar interacts with aqueous environment
3. Mutation (A replaces C):
● Disrupts base pairing → DNA bulge → repair enzymes may correct
Review Questions
4. Dehydration synthesis forms: water + polymers
5. Polymer breakdown: hydrolysis
6. Reaction forming ethyl ethanoate: condensation
7. Example monosaccharide: glucose
Summary Notes for Students
● Scientific method: Observation → Question → Hypothesis → Prediction → Experiment → Result →
Conclusion
● Reasoning: Inductive = general conclusion from observations; Deductive = prediction from general
principle
● Cell theory: Cells are the smallest unit of life
● Macromolecules: Formed via dehydration synthesis, broken by hydrolysis
● Buffers: Maintain pH homeostasis in cells
● Carbon: Central to life due to tetravalent bonding
● Weak interactions: Hydrogen bonds & van der Waals maintain molecular structure
3/18/2026, 8:31:22 PM
#@&(&$)(&#)($#)(#$)()(*)_#)%#**_%#
OpenStax
Biology 2e –
Instructor
Answer Guide
3/18/2026, 8:31:22 PM
,Page 2
#@&(&$)(&#)($#)(#$)()(*)_#)%#**_%#
Unit 1: The Chemistry of Life
Chapter 1: The Study of Life
Visual Connection Questions
1. Apply the scientific method to a toaster problem:
● Observation: My toaster doesn’t toast my bread.
● Question: Why doesn’t my toaster work?
● Hypothesis: There is something wrong with the electrical outlet.
● Prediction: If something is wrong with the outlet, my coffeemaker also won’t work when plugged into
it.
● Experiment: Plug the coffeemaker into the outlet.
● Result: Coffeemaker works.
Conclusion: The hypothesis is incorrect.
Alternative hypotheses: The toaster might be broken or was not turned on.
2. Inductive or deductive reasoning:
1. Inductive
2. Deductive
3. Deductive
4. Inductive
3. False statement:
● b. Communities exist within populations which exist within ecosystems. (Correct hierarchy
is population → community → ecosystem)
Review Questions
4. First forms of life: microorganisms
5. Suggested, testable explanation: hypothesis
6. Not a natural science: computer science
7. Logical thinking from observations to conclusion: inductive reasoning
8. Process ensuring research is original and significant: peer review
9. Plants grow faster with music example: inductive reasoning
10. Smallest unit of life: cell
11. Why viruses aren’t living: not made of cells
12. Membrane-enclosed nucleus characteristic: eukaryotic cells
13. Group of same-species individuals: population
14. Hierarchy of biological organization (largest → smallest): biosphere, ecosystem, community,
population, organism
15. Most recently evolved organism in phylogenetic tree: branch tips
Critical Thinking Questions
16. Scientific method applied to everyday life:
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● Example: Car won’t start → hypothesis: dead battery → experiment: replace or charge battery → check if
car starts.
17. Applied science example: Vaccines preventing diseases like polio, measles, and influenza.
18. Topics inside biology: disease mechanisms, plant responses, environmental impact on species
Topics outside biology: rock formation, planetary orbits
19. Cancer example:
● Basic science: What evolutionary purpose might cancer serve?
● Applied science: What interventions prevent cancer at the cellular level?
20. Two criteria for life and nonliving examples:
● Criteria: organization and regulation
● Nonliving examples: sedimentary rocks, technology
21. Levels of organization (smallest → largest):
Hydrogen atom → water molecule → skin cell → liver → elephant → wolf pack → tropical rainforest →
planet Earth
22. Homeostasis example: Sweating cools body; thirst triggers water intake to maintain hydration.
23. Microscopic to global study:
● Cell → tissue → organ → organism → population → community → ecosystem → biosphere
Chapter 2: The Chemical Foundation of Life
Visual Connection Questions
1. Neutrons in carbon isotopes:
● Carbon-12 → 6 neutrons
● Carbon-13 → 7 neutrons
2. Electron gain/loss for stable configuration:
● Group 1 → lose 1 electron
● Group 14 → gain 4 electrons
● Group 17 → gain 1 electron
3. False statement about enantiomers:
● Must have at least three different groups connected to central carbon (should be four)
Review Questions
4. Xenon neutrons: 108 − 54 = 54
5. Atoms differing in neutron number: isotopes
6. Potassium electron configuration: shells 1–3 full, shell 4 has 1 electron
7. Weak chemical bond: hydrogen bond
8. False statement: water is the most abundant molecule in the atmosphere
9. Acids added → pH decreases
10. Molecule binding H⁺ → base
11. True: acids and bases neutralize each other
12. Carbon can bond with 4 other atoms
13. Not a functional group: sodium
Critical Thinking Questions
14. Ionic vs covalent bonds:
● Ionic: electron transfer, moderate strength
● Covalent: electron sharing, stronger
15. Importance of hydrogen bonds/van der Waals:
● Maintain structure of proteins and DNA for proper function
16. Buffer function:
● Absorb H⁺ or OH⁻, prevent pH swings (e.g., bicarbonate system)
17. Insects walking on water:
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● Surface tension due to cohesion between water molecules
18. Carbon’s importance:
● Forms up to 4 covalent bonds, allows large, complex molecules
19. Saturated vs unsaturated triglycerides:
● Saturated: no double bonds, solid
● Unsaturated: ≥1 double bond, liquid
Chapter 3: Biological Macromolecules
Visual Connection Questions
1. Sugar types:
● Glucose, galactose → aldose
● Fructose → ketose
2. Amino acid distribution:
● Soluble proteins → polar/charged outside, nonpolar inside
● Membrane proteins → nonpolar with lipid tails, polar interacts with aqueous environment
3. Mutation (A replaces C):
● Disrupts base pairing → DNA bulge → repair enzymes may correct
Review Questions
4. Dehydration synthesis forms: water + polymers
5. Polymer breakdown: hydrolysis
6. Reaction forming ethyl ethanoate: condensation
7. Example monosaccharide: glucose
Summary Notes for Students
● Scientific method: Observation → Question → Hypothesis → Prediction → Experiment → Result →
Conclusion
● Reasoning: Inductive = general conclusion from observations; Deductive = prediction from general
principle
● Cell theory: Cells are the smallest unit of life
● Macromolecules: Formed via dehydration synthesis, broken by hydrolysis
● Buffers: Maintain pH homeostasis in cells
● Carbon: Central to life due to tetravalent bonding
● Weak interactions: Hydrogen bonds & van der Waals maintain molecular structure
3/18/2026, 8:31:22 PM
