MCMASTER BIO 1M03 EXAM 2025
QUESTIONS AND ANSWERS
Why might Pasteur's experiment be inconclusive? - ANS The swan-necked flask broth may
not support cell growth, or the broth was poisoned. Experiment did not confirm hypothesis that
all cells come from pre-existing cells
Why are replicates important in experiments? - ANS To ensure that results were not
achieved by random chance
What is the definition of a replicate? - ANS Unit that shares a common thing (4 mice in one
cage = 1 replicate)
What does the law of succession suggest? - ANS As one species disappears, a similar one
appears. Suggests ancestors and descendants
What is the difference between vestigial traits and transitional features? - ANS vestigial -
useless features similar to useful features in related species (eg, coccyx in humans, tail in
monkeys)
transitional - intermediate feature seen in fossil species, between ancestral and descended
species (eg, aquatic animal fins, tetrapod limbs)
List potential outcomes of the bottleneck effect - ANS - Potential high frequency of
deleterious alleles that were previously at low frequency in source population
- Different allele frequencies from source population, could lead to speciation
- Strong genetic drift due to small population size
1
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, Explain how the tuberculosis bacteria underwent natural selection during and after drug
therapy - ANS Variation: different strains → some resistant to drugs, some died
Heritability: drug-resistant bacteria passed drug-resistant gene to daughter cells
Differential fitness: bacteria that survived produced offspring
Selection: drug-resistant allele had higher chance of survival through drug therapy
Give three types of homologies. Provide an example for each - ANS Genetic: similarity in
RNA, DNA, amino acids (eg, AUG start codon shared with many living organisms)
Developmental: similarities in embryonic form or developmental processes (eg, embryos of
human, chicken, cat)
Structural: similarity in adult features (eg, neck bone structure shared between giraffes and
humans)
What is the difference between acclimatization and adaptation? - ANS Acclimatization:
organism's response to the environment
Adaptation: heritable trait that increases the fitness of an individual. Acclimatization does not
change alleles, therefore it is not heritable.
How are the Galapagos finches an example of directly observed evolution? - ANS Beak
morphology and body size is heritable, and changes due to the environment. Since evolution =
∆ in allele frequencies, selection for deeper beaks kills medium beaks. ∆ in food source selects
for smaller beaks, which changes allele frequencies again.
How does the Galapagos finches exhibit non-Lamarckian evolution? - ANS Lamarckian
evolution says evolution is goal directed. Bidirectional evolution (deeper to smaller) goes
against this; if it was goal, it would've gone in a single direction.
`Provide examples where evolution is not goal-directed - ANS - Parasites lose complex
digestive systems
- Finch beaks get larger, then smaller
2
Page
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, Why can humans not fly? What constraints are in place? - ANS - Historical constraints: since
all traits come from previous traits, if we don't have a prior trait for flying, we won't develop
flight
- Genetic: we lack the necessary genes that would give us wings, flight, etc.
Individuals with genotype XX have same phenotype as genotype XY. Which allele is dominant,
and what are individuals with intermediate phenotypes called? - ANS X is dominant, Y is
recessive. Incompletely dominant.
What is evolution driven by? Of the four, which one introduces new alleles? - ANS Natural
selection, gene flow, genetic drift, mutation. Mutation is the only one that introduces new
alleles into populations (other than gene flow)
For a given population, there is more observed heterozygotes than predicted in HWE. What are
some reasons this might occur? - ANS - 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? - ANS - 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? - ANS 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? - ANS - Facing selection to
develop characteristics that reinforce sexual isolation
3
- Develop traits that provide edge over competing species for resources
Page
@COPYRIGHT FYNDLAY 2025/2026
QUESTIONS AND ANSWERS
Why might Pasteur's experiment be inconclusive? - ANS The swan-necked flask broth may
not support cell growth, or the broth was poisoned. Experiment did not confirm hypothesis that
all cells come from pre-existing cells
Why are replicates important in experiments? - ANS To ensure that results were not
achieved by random chance
What is the definition of a replicate? - ANS Unit that shares a common thing (4 mice in one
cage = 1 replicate)
What does the law of succession suggest? - ANS As one species disappears, a similar one
appears. Suggests ancestors and descendants
What is the difference between vestigial traits and transitional features? - ANS vestigial -
useless features similar to useful features in related species (eg, coccyx in humans, tail in
monkeys)
transitional - intermediate feature seen in fossil species, between ancestral and descended
species (eg, aquatic animal fins, tetrapod limbs)
List potential outcomes of the bottleneck effect - ANS - Potential high frequency of
deleterious alleles that were previously at low frequency in source population
- Different allele frequencies from source population, could lead to speciation
- Strong genetic drift due to small population size
1
Page
@COPYRIGHT FYNDLAY 2025/2026
, Explain how the tuberculosis bacteria underwent natural selection during and after drug
therapy - ANS Variation: different strains → some resistant to drugs, some died
Heritability: drug-resistant bacteria passed drug-resistant gene to daughter cells
Differential fitness: bacteria that survived produced offspring
Selection: drug-resistant allele had higher chance of survival through drug therapy
Give three types of homologies. Provide an example for each - ANS Genetic: similarity in
RNA, DNA, amino acids (eg, AUG start codon shared with many living organisms)
Developmental: similarities in embryonic form or developmental processes (eg, embryos of
human, chicken, cat)
Structural: similarity in adult features (eg, neck bone structure shared between giraffes and
humans)
What is the difference between acclimatization and adaptation? - ANS Acclimatization:
organism's response to the environment
Adaptation: heritable trait that increases the fitness of an individual. Acclimatization does not
change alleles, therefore it is not heritable.
How are the Galapagos finches an example of directly observed evolution? - ANS Beak
morphology and body size is heritable, and changes due to the environment. Since evolution =
∆ in allele frequencies, selection for deeper beaks kills medium beaks. ∆ in food source selects
for smaller beaks, which changes allele frequencies again.
How does the Galapagos finches exhibit non-Lamarckian evolution? - ANS Lamarckian
evolution says evolution is goal directed. Bidirectional evolution (deeper to smaller) goes
against this; if it was goal, it would've gone in a single direction.
`Provide examples where evolution is not goal-directed - ANS - Parasites lose complex
digestive systems
- Finch beaks get larger, then smaller
2
Page
@COPYRIGHT FYNDLAY 2025/2026
, Why can humans not fly? What constraints are in place? - ANS - Historical constraints: since
all traits come from previous traits, if we don't have a prior trait for flying, we won't develop
flight
- Genetic: we lack the necessary genes that would give us wings, flight, etc.
Individuals with genotype XX have same phenotype as genotype XY. Which allele is dominant,
and what are individuals with intermediate phenotypes called? - ANS X is dominant, Y is
recessive. Incompletely dominant.
What is evolution driven by? Of the four, which one introduces new alleles? - ANS Natural
selection, gene flow, genetic drift, mutation. Mutation is the only one that introduces new
alleles into populations (other than gene flow)
For a given population, there is more observed heterozygotes than predicted in HWE. What are
some reasons this might occur? - ANS - 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? - ANS - 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? - ANS 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? - ANS - Facing selection to
develop characteristics that reinforce sexual isolation
3
- Develop traits that provide edge over competing species for resources
Page
@COPYRIGHT FYNDLAY 2025/2026
