AP Biology Practice Exam 1 ❮ 277
environmental conditions. Commensalism is
when one organism benefits while the other
is unaffected. Mutualism is when both organ-
isms reap benefits from the interaction.
Parasitism is when one organism benefits at the
other’s expense. Competition is the situation in
which organisms fight for some limited resource.
- B
- A—Cholesterol is one of the lipids that serves as the
starting point for the synthesis of sex hormones.
- C
- D—Purines have a double-ring structure; pyrim-
idines, a single-ring one.
- B—The ribosome is the site of protein synthesis.
- C
- A
- B
- D
- D
- A
- E
- C
- B—Testosterone level is an adaptive trait in this
population, one that has been molded by natural
selection (or possibly sexual selection; we cannot
determine this from the question) to aid in repro-
duction. Adaptive radiation is a process by which
many speciation events occur in a newly exploited
environment and does not apply here. This is not
an example of divergent selection because both
breeding and nonbreeding males have low testos-
terone levels during at least one part of the year; if
the two male types always differed in testosterone
level, this population could eventually split into
two populations. Development and sperm pro-
duction may be related to testosterone but are not
addressed in this experiment.
- D—Since testosterone levels are increased only
during the breeding season, we can infer that
testosterone has some role in breeding. Since
reproductive males express higher testosterone
levels only during the breeding season, we
hypothesize that testosterone is beneficial, as
opposed to detrimental, to breeding.
37. A—Since testosterone seems to be linked with
reproduction, we infer from the new data that
the “nonbreeding” males are actually breeding
and therefore have elevated testosterone levels.
Females, population growth, and number of offspring
produced are not considered in this example.
Finally, although testosterone does affect many
physiological processes, none of these are dis-
cussed or illustrated in this example.
38. C—Although several processes can affect the
frequency of a new phenotype or genotype, once
it is in place, the original genetic change must
have been the result of a mutation (probably a
chromosomal aberration).
39. B—No physical barrier separated the two popu-
lations; this is therefore an example of sympatric,
not allopatric speciation. The other answer
choices are not types of speciation.
40. D—Polyploidy is the only answer that can
describe an individual.All the others are processes
or states that describe population events.
Polyploidy is the duplication of whole chromo-
somes that leads to speciation because the new
variety can no longer breed with the original.
41. C—Polyploidy is much more common in plants;
mutations such as the duplication of whole chro-
mosomes are usually lethal to animals.
42. C—Gel electrophoresis separates DNA on the
basis of size. Smaller samples travel a greater
distance down the gel compared to larger
samples.
43. B—His DNA fingerprint seems to exactly match
that of the evidence DNA sample.
44. B—A and C seem to share the exact same restric-
tion fragment cut of their DNA. Perhaps they
are messing with our heads and added the DNA
from the same individual twice.
45. B—100− 45 − 36 =19 percent.
46. C—36 percent of the population is AA. Taking
the square root of 0.36, we find the frequency of
the A allele to be 0.6. This means that the a
allele’s frequency must be 1 −0.6, or 0.4. From
these numbers, we can calculate the expectedHardy-
Weinberg heterozygous frequency is 2pq =
2(A)(a)=2(0.6)(0.4)=48.0 or 48 percent.
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