EXAM 1 (NATS 104, Spring 2003)
KEY TO EXAM 1(average was 84%)
1. Which of the following was found to be important in the study on widowbirds? (1)
a. male-male competition
b. genetic drift
c. female mating preference
d. infection by parasites
2. Which factor(s) below can cause populations to evolve (circle all that apply)? (1)
a. mutation
b. non-random mating
c. gene flow
d. genetic drift
e. natural selection
f. ALL OF THE ABOVE.
3. Which of the following terms describes the situation in which individuals within a subset
of a population are more likely to mate with each other than with individuals from the
population at large? (1)
a. gene flow
b. genetic drift
c. nonrandom mating
d. random mating
4. This is the original source of all genetic variation. (1)
a. mutation
b. genetic drift
c. gene flow
5. This is the process by which individuals with particular heritable characters survive and
reproduce at a higher rate than other individuals in a population. (1)
a. natural selection
b. adaptation
c. genetic drift
d. gene flow
6. In response to a drought, the beaks of the ground finch on the Galapagos islands: (1)
a. were larger on average in subsequent generations
b. were smaller on average in subsequent generations
c. did not change in size.
7. Which of the following were found to be important in the study on widowbirds? (1)
Everyone got 1 pt for this
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EXAM 1 (NATS 104, Spring 2003)
Name_____________________________
8. How did larval aggregations of the blister beetle fool male bees? (1)
Looked and/or smelled like female bees
9. What kind of selection was occurring in the male widowbirds? Sexual (1)
Natural (.5)
10. Describe one strategy that male animals have evolved to help their sperm compete in
species with high female promiscuity (from Dr. Tatiana). (1)
Plug up females after mating so that they cannot mate again/ Long mating bouts /
chemicals in sperm to kill other sperm / removing the sperm of other males before they
mate with them (using bottlebrush penises, for example in dragonflies) / guarding
females after mating with them to keep other males away.
11. Provide an example of convergent evolution and describe how it is evidence for
evolution. (2)
Dolphins and Sharks shape, fins., countershading (coloration) / aloe and cactus / bird wing
and bat wing and insect wing /
These examples are of organisms that have similar body form and fin form due to
converging on the same body shape in the same environment. They have converged on the
same form independently even though they are distantly related; so their similar form is
due to adaptation to living in the same environment rather than to common ancestry.
12. a ) Provide two examples of adaptations in non-human animals. (2 pts)
camouflage coloration in many animals (white fur in polar bears), thick fur in cats, ability
to lose fur when it is hot and to grow more fur when it is cold in cats, ability to
communicate by song in whales, building a bower (a bowerbird), building a nest, using a
rock to open a clam (otter), etc., red flowers to attract hummingbird pollinators, seeds with
wings to help them disperse, seeds surrounded by fruit to attract animal dispersers.
b) Provide an example of an adaptation in humans (1 pt).
Cultural: Ability to learn a language, to speak a language, to adapt to a new culture by
learning the local customs, ability to play music or sing or dance.
Physical: hair on body for protection, skin color to protect from UV, upright posture,
opposable thumb,
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EXAM 1 (NATS 104, Spring 2003)
13. Provide one example from your readings or lecture on relatively rapid evolution that we
have been able to observe in recent time. Explain how it is evidence for natural selection.
(HINT: possible ones to choose from would be beak size in the finches on Galapagos,
HIV evolving resistance to antiviral drugs, or bacteria evolving resistance to antibiotics)
(3 pts)
Natural Selection is the differential survival and reproduction of individuals because of
heritable traits they possess that help them to outreproduce other individuals in a
particular environment. Those traits are selected and better represented, relative to other
traits, in future generations.
HIV provides evidence for NS in recent time, in a number of ways. First the increase in the
resistant form of HIV was due to exposure to antivirals causing the resistant forms to be
selected over the wild, non-resistant forms. Second, doctors have been using natural
selection to their advantage in the treatment of HIV. They took patients off of the drugs
once they saw that the resistant forms were dominant and no longer affected by drugs. This
allowed the wild type to increase in abundance due to the absence of drugs, and the ability
of the wild type to outcompete the resistant type in the absence of drugs. Once the wild type
was abundant again, the doctors zapped it with the antiviral drugs to which the wild type is
susceptible. Because HIV changes so quickly, with a high mutation rate, lots of genetic
variability exists within a patient for selection to act on. This causes it to evolve resistance
rapidly, but also to evolve back to a novel, non-resistant form rapidly.
Antibiotics are another example since bacteria have become resistant to antibiotics in recent
time in response to the overuse of antibiotics. Under pressure from the drugs, the resistant forms
of the bacteria are selected for (favored) and rise in prominence. Also, when people do not take
the whole course of antibiotics, but stop early, they are farming resistant forms, by exposing
them to drugs but not letting the drug run long enough to kill the resistant forms off.
14. Infanticide in lions happens when a male lion takes over a pride of females and kills the
cubs of those females sired by the previous male. After the cubs are killed, the females go
into estrus (heat) and can be mated by the new male. How would a biologist explain how
infanticidal behavior evolved in lions? (2 pts)
Originally, lions probably did not have infanticide. A male lion that showed that behavior
when he took over a pride and if it was genetically based, would leave more offspring than
a male lion that did not have the behavior and that spent energy on cubs that did not carry
his genes. Because the male lion with infanticidal behavior has more cubs and they have the
gene for infanticidal behavior as well, it evolves in lions, because the gene frequency for
infanticide has increased and evolution is a change in gene frequency.
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