McMaster Bio 1M03: Exam
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ LATEST 100%
GUARANTEED PASS
For a given population, there is more observed heterozygotes than predicted in HWE. What are
some reasons this might occur? - CORRECT ANSWER-- Non-random mating → subconsciously
prefer heterozygotes
- Natural selection → heterozygotes have an advantage over homozygotes (higher fitness)
In order for HWE to proceed, what assumptions must be made? - CORRECT ANSWER-- random
mating → gametes combine randomly
- no natural selection → parent generation survives and donates gametes
- no genetic drift → population is infinitely large **why does genetic drift affect small
populations?
- no gene flow → no alleles lost by migration
,- no mutation → no new alleles
Why is low genetic variation bad? - CORRECT ANSWER-If pathogen comes and affects those
certain alleles, it can eradicate entire population since no individuals will be able to survive and
reproduce.
How might a population come under directional selection? - CORRECT ANSWER-- Facing
selection to develop characteristics that reinforce sexual isolation
- Develop traits that provide edge over competing species for resources
Obese babies can have trouble breathing, while tiny babies are prone to pneumonia and other
complicating affectations. What type of selection are babies likely under? - CORRECT ANSWER-
Stabilizing selection → selection for intermediate phenotype, elimination of extremes
How can inbreeding lead to accelerated natural selection? - CORRECT ANSWER-Inbreeding
often results in deleterious recessive alleles. Recessive alleles are under purifying selection
What can cause a species living in sympatry to diverge? What must it overcome? - CORRECT
ANSWER-Disruptive selection, gene flow
What might occur if the offspring of two parents with differing phenotypes is shown to have low
fitness? - CORRECT ANSWER-- Selection for less heritability
- Selection for reinforcement (extreme)
Is genetic drift adaptive? - CORRECT ANSWER-Drift can lead to adaptation, but it is not adaptive
(i.e. cause of natural selection). Drift is RANDOM with respect to allele frequency change
Why is genetic drift more prominent in small populations? - CORRECT ANSWER-Alleles can drift
to fixation or deletion in fewer generations. Law of averages only applies to large quantities.
,How can two similar populations display two entirely different phenotypes? - CORRECT
ANSWER-- Founder effect → small group from source colonizes new area, with different allele
frequencies than source population
- genetic drift leads to random increase/decrease in certain alleles (more prominent in small
populations)
How is gene flow an obstacle to speciation? - CORRECT ANSWER-Gene flow makes populations
more similar → less chance for speciation (occurs in sympatry and allopatry)
Which mechanisms of adaption increase diversity, and decrease? - CORRECT ANSWER-Increase
→ gene flow (recipient), mutation
Decrease → genetic drift, natural selection (increase in certain alleles)
What is implied about the alleles A and a if the genotype Aa has higher fitness than
homozygotes? - CORRECT ANSWER-A and a are incompletely dominant
Most mutations are __________________, some are __________________ - CORRECT
ANSWER-Deleterious (purifying selection), beneficial (natural selection)
How does sex affect allele frequency? - CORRECT ANSWER-Sex does not provide new alleles,
but produces new combinations.
Explain the fundamental asymmetry of sex - CORRECT ANSWER-Eggs are expensive, sperm are
cheap
Females invest more time into offspring, males invest more time into mating
How does sexual selection affect males? - CORRECT ANSWER-Males with heritable traits that
enhance their chance of mating are selected for. Selection acts stronger on males, since
females' pickiness of mates makes them desirable to males.
, The development of flashy colours or special dances in males to attract mates is because... -
CORRECT ANSWER-Males experience greater variation in reproductive success, therefore any
traits that maximize their fitness are selected for
Male gorillas are significantly larger than their female counterparts. Chimpanzees have larger
genitals than gorillas. What do these two statements imply? - CORRECT ANSWER-Male gorillas
fight each other for mating rights with a female (greater sexual dimorphism = greater sexual
selection)
Chimpanzees are social, and use their genitals to maximize fitness (mate often)
What is the criteria for the biological species concepts? What are the advantages and
disadvantages of this concept? - CORRECT ANSWER-Populations must be reproductively isolated
(pre or post zygotic isolation). Pre zygotic is favoured, since there is less wasted effort (inviable
offspring)
Disadvantages → cannot apply to extinct, asexual species. Hard to determine closely related
species if separated by distance
What are the advantages and disadvantages of the morphological species concept? - CORRECT
ANSWER-Advantages → fossil species, diverse groups
Disadvantages → convergent or divergent evolution? Polymorphic species (sexual dimorphism)?
Similar groups but inviable hybrids? Cryptic species (Morphologically identical, different traits)?
What type of species is the ecological species concept applied to? - CORRECT ANSWER-Small
things, like archaea, bacteria, asexual eukaryotes.
Explain the relationship between genetic isolation and genetic divergence - CORRECT ANSWER-
Lack of gene flow leads to genetic isolation. Isolation allows for genetic divergence, which
reinforces for genetic isolation (pre-zygotic mechanisms, reinforcement)
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ LATEST 100%
GUARANTEED PASS
For a given population, there is more observed heterozygotes than predicted in HWE. What are
some reasons this might occur? - CORRECT ANSWER-- Non-random mating → subconsciously
prefer heterozygotes
- Natural selection → heterozygotes have an advantage over homozygotes (higher fitness)
In order for HWE to proceed, what assumptions must be made? - CORRECT ANSWER-- random
mating → gametes combine randomly
- no natural selection → parent generation survives and donates gametes
- no genetic drift → population is infinitely large **why does genetic drift affect small
populations?
- no gene flow → no alleles lost by migration
,- no mutation → no new alleles
Why is low genetic variation bad? - CORRECT ANSWER-If pathogen comes and affects those
certain alleles, it can eradicate entire population since no individuals will be able to survive and
reproduce.
How might a population come under directional selection? - CORRECT ANSWER-- Facing
selection to develop characteristics that reinforce sexual isolation
- Develop traits that provide edge over competing species for resources
Obese babies can have trouble breathing, while tiny babies are prone to pneumonia and other
complicating affectations. What type of selection are babies likely under? - CORRECT ANSWER-
Stabilizing selection → selection for intermediate phenotype, elimination of extremes
How can inbreeding lead to accelerated natural selection? - CORRECT ANSWER-Inbreeding
often results in deleterious recessive alleles. Recessive alleles are under purifying selection
What can cause a species living in sympatry to diverge? What must it overcome? - CORRECT
ANSWER-Disruptive selection, gene flow
What might occur if the offspring of two parents with differing phenotypes is shown to have low
fitness? - CORRECT ANSWER-- Selection for less heritability
- Selection for reinforcement (extreme)
Is genetic drift adaptive? - CORRECT ANSWER-Drift can lead to adaptation, but it is not adaptive
(i.e. cause of natural selection). Drift is RANDOM with respect to allele frequency change
Why is genetic drift more prominent in small populations? - CORRECT ANSWER-Alleles can drift
to fixation or deletion in fewer generations. Law of averages only applies to large quantities.
,How can two similar populations display two entirely different phenotypes? - CORRECT
ANSWER-- Founder effect → small group from source colonizes new area, with different allele
frequencies than source population
- genetic drift leads to random increase/decrease in certain alleles (more prominent in small
populations)
How is gene flow an obstacle to speciation? - CORRECT ANSWER-Gene flow makes populations
more similar → less chance for speciation (occurs in sympatry and allopatry)
Which mechanisms of adaption increase diversity, and decrease? - CORRECT ANSWER-Increase
→ gene flow (recipient), mutation
Decrease → genetic drift, natural selection (increase in certain alleles)
What is implied about the alleles A and a if the genotype Aa has higher fitness than
homozygotes? - CORRECT ANSWER-A and a are incompletely dominant
Most mutations are __________________, some are __________________ - CORRECT
ANSWER-Deleterious (purifying selection), beneficial (natural selection)
How does sex affect allele frequency? - CORRECT ANSWER-Sex does not provide new alleles,
but produces new combinations.
Explain the fundamental asymmetry of sex - CORRECT ANSWER-Eggs are expensive, sperm are
cheap
Females invest more time into offspring, males invest more time into mating
How does sexual selection affect males? - CORRECT ANSWER-Males with heritable traits that
enhance their chance of mating are selected for. Selection acts stronger on males, since
females' pickiness of mates makes them desirable to males.
, The development of flashy colours or special dances in males to attract mates is because... -
CORRECT ANSWER-Males experience greater variation in reproductive success, therefore any
traits that maximize their fitness are selected for
Male gorillas are significantly larger than their female counterparts. Chimpanzees have larger
genitals than gorillas. What do these two statements imply? - CORRECT ANSWER-Male gorillas
fight each other for mating rights with a female (greater sexual dimorphism = greater sexual
selection)
Chimpanzees are social, and use their genitals to maximize fitness (mate often)
What is the criteria for the biological species concepts? What are the advantages and
disadvantages of this concept? - CORRECT ANSWER-Populations must be reproductively isolated
(pre or post zygotic isolation). Pre zygotic is favoured, since there is less wasted effort (inviable
offspring)
Disadvantages → cannot apply to extinct, asexual species. Hard to determine closely related
species if separated by distance
What are the advantages and disadvantages of the morphological species concept? - CORRECT
ANSWER-Advantages → fossil species, diverse groups
Disadvantages → convergent or divergent evolution? Polymorphic species (sexual dimorphism)?
Similar groups but inviable hybrids? Cryptic species (Morphologically identical, different traits)?
What type of species is the ecological species concept applied to? - CORRECT ANSWER-Small
things, like archaea, bacteria, asexual eukaryotes.
Explain the relationship between genetic isolation and genetic divergence - CORRECT ANSWER-
Lack of gene flow leads to genetic isolation. Isolation allows for genetic divergence, which
reinforces for genetic isolation (pre-zygotic mechanisms, reinforcement)
