5 Steps to a 5 AP Biology, 2014-2015 Edition
AP Biology Practice Exam 1 ❮ 283
- Mentioning, as an example of postzygotic
barriers, any of the following (1 ⁄ 2 point
each, up to 1 point total for postzygotic
barrier examples): (a) hybrid breakdown—
sometimes the first generation of hybrids
produced are able to reproducewith each
other, but after that the wheels come off and
the next generation is infertile; (b) reduced
hybrid viability—the two different species
are able to mate physically and the hybrid
zygote is formed, but problems arise during
the development of the hybrid that lead to
prenatal death of the individual; (c) reduced
hybrid fertility—the two different species are
able to mate physically and produce a viable
offspring, but the offspring is infertile.
- Life on Earth is made possible because of certain
unique characteristics of water. (maximum
4 points for entire question)
A. Properties of water (maximum 2 points)
- Mentioning that hydrogen bonding holds
water molecules together (cohesion).
(1 point)
- Mentioning that water has high specific
heat (water changes its temperature less
than most substances when it absorbs or
loses a certain amount of heat). (1 point)
- Mentioning that the solid form of water is
less dense than its liquid form. (1 point)
- Mentioning water acts as a solvent for so
many substances. (1 point)
B. Effects on living organisms (maximum 2
points)
- Mentioning that hydrogen bonding
allows for flow of water through plants
(xylem). (1 point)
- Mentioning that water’s high specific heat
means large bodies of water store heat and
leads to milder climates in coastal areas.
(1 point)
- Noting that water’s unusual density
means ice floats. If it sank, all bodies of
water would freeze solid from the bottom
up, and sustainable life on Earth would
not be possible. (1 point)
- Mentioning that water’s ability as a sol-
vent allows for many reactions to occur in
the cell. (1 point)
- Evolution is the change in allele frequencies in a
population over time. (maximum 4 points for
entire question)
A. Definition and examples (maximum 2 points)
- Defining natural selection. (maximum
1 point)
a. Mentioning it is the process by which cer-
tain alleles increase in frequency in a pop-
ulation because of the survival or
reproduction benefit they give to those
individuals who possess them. (1/2 point)
b. Possible example: sickle cell allele per-
sists in populations where malaria is
present (having sickle-shaped red
blood cells makes you less likely to
contract malaria). (1/2 point)
c. Defining genetic drift. (maximum
1 point)
d. Describing how random processes can
change allele frequencies. (1/2 point)
e. Possible example: allele frequencies in
a new population are dependent on
which alleles are present in the
founders of that population (founder
effect). (1/2 point)
- Defining mutation.
a. Mentioning that changes in DNA
create genetic variation and new alleles.
(1/2 point)
b. Mentioning that evolution by “neutral
mutations” can occur even if the new
alleles are not acted on by natural selec-
tion. (1/2 point)
c. Possible example: eye color gene mutates
to a different color without any change
in vision or behavior as a result of the
mutation. (1/2 point)
B. Explanation of data (maximum 2 points)
- Mentioning the changes could not be the
gradual process of natural selection
because they occurred rapidly between
two censuses. (1 point)
- Indicating that the changes could be
caused by genetic drift. (1 point)
- Indicating that the changes could be caused
by some environmental event (flood, fire)
that randomly killed many dark-coated
mice. (1 point)
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