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!
Please do not write on this form, do not forget to put your name on the scantron, do not talk,
‘exchange ideas’, glance over to your neighbor or use your cellphone at any time. If you are
done, stay quiet and respect those that have not yet finished.
1) The function of the acrosomal complex (acrosome; see Figure 1 below) during fertilization is _____.
A) to block polyspermy
B) to dissolve the coating of the egg
C) to nourish the sperm mitochondria
D) to permit maximum sperm motility
Answer B
2. The precursor of the brain and spinal cord as formed by folding of the ectoderm is called the
__________________.
A) Notochord
B) Blastopore
C) Neural Tube
Answer C
3) Many crustaceans (e.g., lobsters, shrimp, and crayfish) use their tails to swim, but crabs have
reduced tails that curl under their shells and are not used in swimming. This is an example of
_____.
A) an adaptation
B) a homologous structure
C) natural selection
D) a vestigial trait
Answer: D
4) Which of these conditions are always 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 1 and 2
D) Conditions 2 and 3
E) Conditions 1, 2, and 3
Answer: C
5) A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the
triazine works well and almost all the pigweed dies; but after several years, the farmer sees more
and more pigweed. Which of these explanations best describes this observation?
A) The herbicide company lost its triazine formula and started selling poor-quality triazine.
B) Natural selection caused the pigweed to mutate, creating a new triazine-resistant species.
C) Triazine-resistant pigweed has less-efficient photosynthesis metabolism.
D) Only triazine-resistant weeds survived and reproduced, so each year more pigweed was
triazine-resistant.
Answer: D
6) Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body
size is not correlated with risk of hawk predation, although small iguanas can sprint faster than
large iguanas. If predators (e.g., cats) that preferably catch and eat slower iguanas are introduced
to the island, iguana body size is likely to _____ in the absence of other factors; the iguanas
would then be under _____ selection.
A) increase; directional
B) increase; disruptive
C) decrease; directional
D) decrease; disruptive
E) stay the same; stabilizing
Answer: C
7) Which of the following is the most predictable outcome of increased 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
E) increased genetic drift
Answer: D
8) Which of the following does not tend to promote speciation?
A) the founder effect
B) gene flow
C) natural selection
D) polyploidy
E) disruptive selection
Answer: B
9) There is an island in the middle of a large river that houses a large population of ants.
Damming of the river causes the island to flood and only the highest points of the island are now
above water. The ants cannot swim, so are now in multiple isolated populations. Which of the
following best describes this event?
A) isolation by dispersal
B) isolation by vicariance
C) a form of sympatric speciation
D) only a rare development of polyploidy could lead to speciation in this case.
E) speciation will not occur in this case because of gene flow
Answer: B
10) A small number of birds arrive on an island from a neighboring larger island. This small
population begins to adapt to the new food plants available on the island, and their beaks begin to
change. About twice a year, one or two more birds from the neighboring island arrive. What
effect do these new arrivals have?
A) Their arrival speeds the process of speciation.
B) Their arrival tends to promote adaptation to the new food plants.
C) Their arrival tends to slow down adaptation to the new food plants.
D) Their arrival represents a colonizing event.
Answer: C
11) A storm brings two formerly separated populations of beetles together. They look very
similar. Under the biological species concept, which of the following would show that the two
populations are different species?
A) One population breeds in spring, the other in fall.
B) Males of the two populations have slightly different flight patterns in courtship.
C) Males from one population are slightly larger than males from the other population.
D) All of the above are correct.
E) None of the above is correct.
Answer: A
12) There is a population of beetles that typically have black wings. A scientist studying these
beetles knows that their eggs hatch in early spring, the baby insects grow through the late spring
and summer, they lay eggs in the early fall, and die in the early winter. Recently some beetles
have been born with white wings. Early in life the black and white winged beetles seem to be
very similar in number of mating events, eggs laid, and survival rates, but shortly after laying
their eggs the white beetles die and there are only black winged beetles during the late fall.
Which of the following is a true statement about the beetles?
A) White and black winged beetles have equal fitness.
B) Black winged beetles have a higher fitness than white winged beetles.
C) The number of baby white winged beetles will decrease in frequency over time.
D) White wings are an adaptation.
Answer: A
13) Which of the following organisms would be most likely to fossilize?
A) a rare worm
B) a common worm
C) a rare squirrel
D) a common squirrel
Answer: D
14) Some beetles and flies have antler-like structures on their heads, much like male deer do.
Antlers in beetle, fly, and deer species with strong male-male competition is an example of
_____.
A) analogous traits (homoplasy)
B) homology
D) parsimony
Answer: A
15) A ___________ is a trait found in certain groups of organisms that exist in no others.
A) hybridization
B) clade
C) synapomorphy
Ans: C
16) Sexual selection __________ the Hardy-Weinberg Principle and ____________ lead to
changes in allele frequency, and thus evolution, over time.
A) follows, cannot
B) follows, can
C) violates, cannot
D) violates, can
Ans: D
17) Mating between direct relatives, such as brothers or sisters, is called:
A) hybridization
B) inbreeding
Ans: B
18) The following can trigger adaptive radiations:
A) genetic drift and sexual selection
B) genetic drift
C) sexual selection
D) morphological innovation and ecological opportunity
Ans: D
19) Directional selection tends to:
A) increase genetic variation
B) reduce genetic variation
C) keep genetic variation equal/stable
Ans: B
20) Male-male competition is just one form of sexual selection. What is the other one?
A) Sexual dimorphism
B) inbreeding
C) Female Choice
Ans: C
Bonus 1) Are traits acquired through an individual’s life inherited by its offspring?
A) Yes
B) No
Ans: B
Bonus 2) The biggest extinction event ever to take place on earth happened at the end of the
________ era, and is hence called the ___________ extinction.
A) Cambrian, End-Cambrian
B) Jurassic, End-Jurassic
C) Permian, End-Permian
Ans: C