Download Genetic drift

Honors Biology: Chapter 15 Review
1.
If evolution is the change in allelic frequencies of a population over time, what causes it to happen? (There are
five things!) natural selection, mutation, gene flow, genetic drift (as a result of a small population) and
nonrandom mating
2. What are two causes of genetic drift? Population bottleneck and founder effect
3.
Draw a picture showing a population before and after recovering from a bottleneck. Your picture should clearly
show how this affects genetic diversity.
Initial Population
Bottleneck
Population After Recovery
ABCDEF
GHIJKLM
ABEFAB
ABEF
ABEFEF
4. Draw a picture showing the founder effect. Show the parent population the founders and the founding
population many generations later. Be sure to how this affects genetic diversity.
Parent Population
ABCDEF
GHIJKLM
Founders
AB
B
Founding Population Later
ABABAB
ABABAB
5. Why is genetic diversity important in populations?
Increase the chance that some individuals will have the variations necessary to survive as environmental
conditions change. Increase fitness of population. Decrease risk of extinction. Lower chance of having to
inbreed and the negative effects associated with it.
6. What type of selection is occurring in each of the following examples:
a. Large lizards are easily seen and captured by birds. Small lizards cannot escape predation by snakes.
Stabilizing
b. Male/Male competition and female choice direct this form of selection. Sexual
c. Ducks with short bills are able to obtain food floating on the pond surface. Ducks with long bills can obtain
food on the bottom of the pond. Disruptive
d. Only the thickest bills are able to crack the nuts, the only available food source. Directional
e. The most colorful male fish have the most success attracting a mate. Sexual
7. True or False. If the statement is false explain why.
Most natural populations are in equilibrium. False; most are evolving
Mutations arise in response to changes in the environment. False, mutations arise by random chance
Genetic drift has a larger impact on small populations.True
Natural selection acts on individual genotypes. False, individual phenotypes
Populations evolve, not individuals. True
Competition between members of the same species results in coevolution. False coevolution occurs between
different species (different species evolve in response to one another)
Components of the abiotic environment that act as agents of natural selection are predation and competition.
False these are components of the biotic environment
Low genetic diversity in elephant seals and cheetahs are the result of the founder effect. False, population
bottleneck
Sum total of all the alleles in a Term that describes when a
population
population is not evolving
Gene Pool
Genetic equilibrium
Form of selection that acts on
traits that allow an individual
to acquire a mate.
Sexual
Changes in allelic frequencies
due to random chance events
Changes in the DNA that
result in new variations in a
population
mutation
The movement of genes
between populations
Genetic drift
Gene flow
Form of selection that favors
the average for of a trait and
selects against the extreme
forms.
Stabilizing
Traits or characteristics that
help an individual survive and
reproduce.
Adaptation
A group of individuals
belonging to the same species
living in the same geographic
area. population
When two species evolve in
response to one another
coevolution
Form of selection that favors
one extreme form of a trait
and selects against the
average and other extreme.
When two or more
phenotypes are maintained in
a population due to selective
advantage of the
directional
When both extreme forms of
a trait are favored and the
average is selected against.
disruptive
Measured by the number of
offspring an individual leaves
behind
fitness
heterozygote.
Balanced polymorphism
Individuals with favorable
variations have the greatest
reproductive success
Natural selection