BIO 180 – Instructor: Yntze van der Hoek
Class test II, 20 MC questions, each worth 5 points, to a total of 100 points. At the end, you will
find two bonus questions. These are both worth 5 points, giving you the opportunity to score a
whopping 110 points on this exam! Go for it!
1) What happens during gastrulation?
A) The neural tube forms.
B) The three embryonic tissue germ layers form.
Answer: B
2) Why was Darwin and Wallace's theory of evolution by natural selection revolutionary?
A) It was the first theory to refute the ideas of special creation.
B) It proved that individuals acclimated to their environment over time.
C) It dismissed the idea that species are constant and emphasized the importance of variation and
change in populations.
D) It was the first time a biologist had proposed that species changed through time.
Answer: C
3) Which of these conditions is/are not true of populations evolving due to natural selection?
Condition 1: The population must vary in traits that are heritable.
Condition 2: Some heritable traits must increase reproductive success.
Condition 3: Individuals pass on all traits they acquire during their lifetime.
A) Condition 1 only
B) Condition 2 only
C) Conditions 3 only
D) Conditions 2 and 3
E) Conditions 1, 2, and 3
Answer: C
4) Which of the following is the best modern definition of evolution?
A) descent without modification
B) change in allele frequencies in a population over time
C) inheritance of acquired characters
Answer: B
5) Claytonia virginica is a woodland spring herb with flowers that vary from white to pale pink
to bright pink. This plant is primarily pollinated by a bee that prefers pink flowers to white
flowers. Claytonia with pink flowers have greater relative fruit set (i.e. they reproduce more)
than Claytonia with white flowers. Nevertheless, the percentage of different flower colors
remains stable in the study population from year to year. Which of these statements might
explain this observation?
A) Reproductive success does not affect evolution in this species.
B) Flower color is not heritable but is instead environmentally determined.
C) The white flowers have evolved pollinator resistance.
Ans: B
6) What it mean when an allele is ‘fixed’ (i.e. reaches ‘fixation’)?
A) it means that the allele is the dominant allele
B) it means that the allele is eliminated from the population
C) it means that the allele has a frequency of 1.0 (i.e. it is the only allele in the population)
Answer: C
7) Two researchers found that large marine iguanas (found on the Galapagos Islands) had higher
reproductive success than smaller iguanas did. However, the large iguanas were generally in
poor body condition because they could not eat enough. Interestingly, the efficiency of foraging
improves at higher temperatures, allowing iguanas to eat more. Thus, knowing that global
warming leads to a gradual increase in air and water temperatures in the Galápagos Islands, the
researchers hypothesized that iguana size will _____ over the next decades/centuries .
A) increase
B) decrease
C) stabilize around the mean body size
Answer: A
8) A biologist doing a long-term study on a wild spider population observes that variation in silk
thickness is increasing generation after generation. Which of the following could the spider
population be experiencing?
A) directional selection on silk thickness
B) stabilizing selection on silk thickness
C) disruptive selection on silk thickness
Answer: C
9) Which of the following is the most predictable outcome of decreased gene flow between two
populations?
A) lower average fitness in both populations
B) higher average fitness in both populations
C) increased genetic difference between the two populations
D) decreased genetic difference between the two populations
Answer: C
Figure 1
10) Refer to Figure 1. Male reproductive success, measured as the number of offspring surviving
to adulthood, is found for two closely related beetle species and graphed above. Which of these
statements would you expect to be true of sexual dimorphism in the two species?
A) Species A should have greater sexual dimorphism than species B.
B) Species B should have greater sexual dimorphism than species A.
C) Species A and B should have about equal amounts of sexual dimorphism.
D) Neither species should show any sexual dimorphism.
Answer: A
Figure 2
11) Refer to Figure 26.1. Which of the following forms a monophyletic group?
A) A, B, C
B) C and D
C) B and C
D) D, E, G,
E) all of the above
Answer: A
12) With the term ‘double fertilization’ we simply mean that an organism will give birth to
twins.
A) True
B) False
Ans B
13) Which of the following does not tend to promote speciation?
A) gene flow
B) natural selection
C) polyploidy
Answer: A
14) Natural selection for traits that keep distinct populations from reproducing with each other is
called reinforcement. When is reinforcement beneficial?
A) when the environment is changing
B) when hybrids have lower fitness than either parent population
C) when gene flow is low
D) Reinforcement is beneficial under all of the above conditions.
Answer: B
15) Bird embryos receive their nutrients through the placenta, which forms:
A) one to two weeks after fertilization
B) directly after gastrulation
C) never. Are you kidding me with this question? Birds do not have a placenta, they lay eggs
with yolk as a source of nutrients.
Ans C
16) Which of the following organisms would be least likely to fossilize?
A) a rare worm
B) a common/abundant worm
C) a rare squirrel
D) a common/abundant squirrel
Answer: A
17) The following are examples of prezygotic isolation except for:
A) Habitat isolation
B) Temporal isolation
C) Hybrid sterility
D) Behavioral isolation
Ans C
18) The geographical area where interbreeding occurs and hybrid offspring are common is
called:
A) habitat
B) ecosystem
C) hybrid zone
Ans: C
19) Female choice is a form of:
A) genetic drift
B) prezygotic isolation
C) inbreeding
D) sexual selection
Ans D
20) Which of the Hardy-Weinberg assumptions is violated by sexual selection:
A) No gene flow
B) No mutation
C) No genetic drift
D) Random mating
Ans D
Bonus questions:
21) Analogous traits are similarities that exist among species that have inherited that trait
from a common ancestor:
A) True
B) False
B
22) The blocks of cell tissue found near (left and right of) the neural tube in an embryo that
undergoes organogenesis, and that will be at the start of cell determination and
specialization, are called:
A) Notochords
B) Somites
C) Blastocoels
Ans: B