PCB 4674 Exam 2 Definitions - Questions with
Correct Answers (Verified Update)
62 questions with answers
Topic: PCB 4674 Exam 2 Definitions
1. Natural selection
Answer: Consistent differences in fitness among different classes of biological entities.
2. Fitness
Answer: Relative number of offspring an entity leaves in the next generation (survival is
built into this).
3. Biological entities
Answer: Examples include genes, cell types, individuals, populations, and species.
4. Adaptation
Answer: A trait that enhances the survival or reproduction of entities that bear it relative to
alternative character states.
5. Altruism
Answer: Unselfish behaviors that benefit others' fitness.
6. Kin selection
Answer: (No definition provided - often refers to selection favoring behaviors that increase
the reproductive success of relatives, even at a cost to the individual.)
7. Green beard effect
Answer: (No definition provided - typically describes a genetic mechanism where individuals
recognize and favor others who share a specific trait or "green beard.")
8. Parthenogenesis
Answer: Asexual reproduction where species reproduce clonally without fertilization.
9. 2-fold cost to sex
Answer: Sexual reproduction has double the cost because individuals reproduce at half the
rate of asexual species.
10. Selective interference
Answer: The chance that a particular allele is passed to the next generation depends on its
genetic background.
11. Intrasexual selection
Answer: Selection within a sex where individuals (usually males) compete among
themselves for access to mates, either directly or indirectly.
12. Intersexual selection
Answer: Selection between sexes where one sex (often males) competes for the attention or
choice of the other (often females).
13. Sexual selection
Answer: Differential reproductive success resulting from variation among individuals in
mating success.
Page 1
, 14. Combat
Answer: Direct physical competition between males for access to females.
15. Post-copulatory competition
Answer: Occurs when females mate with multiple males, leading to competition among
sperm from different males.
16. Infanticide
Answer: The killing of another male's offspring to make the female receptive to mating
again sooner.
17. Sexy-son hypothesis
Answer: The idea that females prefer males with attractive ("sexy") traits so their sons will
inherit these traits and have higher reproductive success.
18. Mutation
Answer: Any change in the genetic material that occurs in individuals and creates
differences in DNA sequences.
19. Substitution
Answer: The replacement in a population of one amino acid or nucleotide by another.
20. Polymorphism
Answer: The presence of two or more variants (alleles) at a DNA locus within a population.
21. Silent (synonymous)
Answer: Substitutions or polymorphisms that do not change the amino acid sequence.
22. Replacement (non-synonymous)
Answer: Substitutions or polymorphisms that do change the amino acid sequence.
23. Genetic drift
Answer: Random changes in allele frequency; probability of fixation: P(fixation) = 1 / (2Ne),
where Ne = effective population size.
24. Natural selection
Answer: Non-random changes in allele frequency driven by fitness differences; probability of
fixation: P(fixation) = 2s, where s = selection coefficient.
25. Expected substitution rate
Answer: The observed amino acid differences between groups are an underestimate of the
true rates; K = -ln(1 - p), where p = proportion of differences.
26. Substitution rate against selection
Answer: Given by k = 4Neuas, where Ne = effective population size, u = mutation rate, a =
selection coefficient, and s = selection intensity.
27. Substitution rate for neutral mutation/drift
Answer: k = (2Neu) × (Ne) = u, meaning the substitution rate equals the neutral
mutation rate.
28. Predictions for neutral theory
Answer: Amino acid and nucleotide substitution rates should remain constant as long as the
neutral mutation rate is constant.
Page 2
Correct Answers (Verified Update)
62 questions with answers
Topic: PCB 4674 Exam 2 Definitions
1. Natural selection
Answer: Consistent differences in fitness among different classes of biological entities.
2. Fitness
Answer: Relative number of offspring an entity leaves in the next generation (survival is
built into this).
3. Biological entities
Answer: Examples include genes, cell types, individuals, populations, and species.
4. Adaptation
Answer: A trait that enhances the survival or reproduction of entities that bear it relative to
alternative character states.
5. Altruism
Answer: Unselfish behaviors that benefit others' fitness.
6. Kin selection
Answer: (No definition provided - often refers to selection favoring behaviors that increase
the reproductive success of relatives, even at a cost to the individual.)
7. Green beard effect
Answer: (No definition provided - typically describes a genetic mechanism where individuals
recognize and favor others who share a specific trait or "green beard.")
8. Parthenogenesis
Answer: Asexual reproduction where species reproduce clonally without fertilization.
9. 2-fold cost to sex
Answer: Sexual reproduction has double the cost because individuals reproduce at half the
rate of asexual species.
10. Selective interference
Answer: The chance that a particular allele is passed to the next generation depends on its
genetic background.
11. Intrasexual selection
Answer: Selection within a sex where individuals (usually males) compete among
themselves for access to mates, either directly or indirectly.
12. Intersexual selection
Answer: Selection between sexes where one sex (often males) competes for the attention or
choice of the other (often females).
13. Sexual selection
Answer: Differential reproductive success resulting from variation among individuals in
mating success.
Page 1
, 14. Combat
Answer: Direct physical competition between males for access to females.
15. Post-copulatory competition
Answer: Occurs when females mate with multiple males, leading to competition among
sperm from different males.
16. Infanticide
Answer: The killing of another male's offspring to make the female receptive to mating
again sooner.
17. Sexy-son hypothesis
Answer: The idea that females prefer males with attractive ("sexy") traits so their sons will
inherit these traits and have higher reproductive success.
18. Mutation
Answer: Any change in the genetic material that occurs in individuals and creates
differences in DNA sequences.
19. Substitution
Answer: The replacement in a population of one amino acid or nucleotide by another.
20. Polymorphism
Answer: The presence of two or more variants (alleles) at a DNA locus within a population.
21. Silent (synonymous)
Answer: Substitutions or polymorphisms that do not change the amino acid sequence.
22. Replacement (non-synonymous)
Answer: Substitutions or polymorphisms that do change the amino acid sequence.
23. Genetic drift
Answer: Random changes in allele frequency; probability of fixation: P(fixation) = 1 / (2Ne),
where Ne = effective population size.
24. Natural selection
Answer: Non-random changes in allele frequency driven by fitness differences; probability of
fixation: P(fixation) = 2s, where s = selection coefficient.
25. Expected substitution rate
Answer: The observed amino acid differences between groups are an underestimate of the
true rates; K = -ln(1 - p), where p = proportion of differences.
26. Substitution rate against selection
Answer: Given by k = 4Neuas, where Ne = effective population size, u = mutation rate, a =
selection coefficient, and s = selection intensity.
27. Substitution rate for neutral mutation/drift
Answer: k = (2Neu) × (Ne) = u, meaning the substitution rate equals the neutral
mutation rate.
28. Predictions for neutral theory
Answer: Amino acid and nucleotide substitution rates should remain constant as long as the
neutral mutation rate is constant.
Page 2
