1. In natural selection, fitness refers to an organism's ability to
A.
live forever
B.
survive and reproduce successfully
C.
grow larger than all other organisms
D.
avoid all environmental changes
Correct Answer:
survive and reproduce successfully
Explanation:
Biological fitness is the ability of an organism to survive and produce offspring that can also reproduce.
2. Which organism has the greatest biological fitness in a population?
A.
An organism that produces no offspring
B.
An organism that survives briefly but cannot reproduce
C.
An organism that survives and produces many fertile offspring
D.
An organism that is the largest in body size
Correct Answer:
An organism that survives and produces many fertile offspring
Explanation:
Fitness depends mainly on successful reproduction, along with survival long enough to reproduce.
3. Natural selection increases the frequency of traits that
A.
reduce survival and reproduction
B.
improve survival and reproductive success
C.
are always the most common traits
D.
make every organism identical
Correct Answer:
improve survival and reproductive success
Explanation:
Traits that help organisms survive and reproduce are more likely to be passed to the next generation.
4. In directional selection, individuals with which trait usually have higher fitness?
A.
An extreme trait in one direction
B.
Only the average form of a trait
C.
Both extreme forms equally
D.
A trait unrelated to survival
Correct Answer:
An extreme trait in one direction
Explanation:
Directional selection favors one extreme phenotype, giving its individuals greater survival or reproductive success.
5. Stabilising selection generally gives the highest fitness to individuals with
A.
a very small value of a trait
B.
an average value of a trait
C.
the largest possible value of a trait
D.
a completely new trait
Correct Answer:
an average value of a trait
Explanation:
Stabilising selection favors intermediate phenotypes and reduces the reproductive success of both extremes.
6. Disruptive selection favors
A.
only individuals with intermediate traits
B.
individuals with both extreme traits
C.
only the smallest individuals
D.
all individuals equally
Correct Answer:
individuals with both extreme traits
Explanation:
In disruptive selection, both extreme phenotypes have greater fitness than the intermediate phenotype.
7. If dark-colored insects survive better on dark tree bark, natural selection will most likely increase the frequency of
A.
dark coloration
B.
all colors equally
C.
light coloration only
D.
colorless bodies only
Correct Answer:
dark coloration
Explanation:
Dark insects have higher fitness in this environment because they are better camouflaged and more likely to survive and reproduce.
8. A bird with a medium-sized beak obtains food more successfully than birds with very small or very large beaks. This is an example of
A.
directional selection
B.
stabilising selection
C.
disruptive selection
D.
artificial selection
Correct Answer:
stabilising selection
Explanation:
The intermediate beak size provides the greatest fitness, while both extreme sizes are less successful.
9. If individuals with either very small or very large body size reproduce more successfully than medium-sized individuals, the selection is
A.
directional selection
B.
stabilising selection
C.
disruptive selection
D.
random selection
Correct Answer:
disruptive selection
Explanation:
Disruptive selection favors both extremes because they have greater reproductive success than the intermediate form.
10. The result of natural selection is most directly seen as a change in the
A.
frequency of advantageous inherited traits in a population
B.
age of every organism in a population
C.
number of traits in one individual during its lifetime
D.
size of the environment
Correct Answer:
frequency of advantageous inherited traits in a population
Explanation:
Natural selection changes populations over generations by increasing inherited traits associated with higher fitness.
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