Download Evolution Practice Questions

Evolution Practice Questions
Chapters 17
Part I. Fill in the blank.
1. __Evolution______ is defined as a change in populations over a period of time.
2. __Fitness__________ in an evolutionary sense means that organisms are successful in
passing on their genes to the next generation.
3. ___Natural_____ selection, or “survival of the fittest,” means that those organisms who
have traits that are better suited to their environment are more likely to survive and reproduce
than those with less desirable traits.
4. Natural selection works on an organism’s Phenotype
rather than its genotype
.
5. A(n) gene pool
consists of all the genes, including the alleles for each gene, that are
present in a population.
6. A gene pool typically contains different alleles
for each heritable trait.
7. The number of times that an allele occurs in a gene pool compared with the number of times
other alleles for the same gene occur is called the allele frequency of the population.
8. In the diagram below, use circles to represent the alleles within each segment of the population.
Draw the B alleles as solid circles and the b alleles as outline circles. The total number of
individuals in this population is 25
; the total number of alleles is 50
.
9.
How many alleles for black fur are in the sample population and what percentage of allele
frequency does that represent?
20 (B) for black fur
20/50(total alleles) = 40% frequency for B
10. How many alleles for brown fur are in the sample population and what percentage of allele
frequency does that represent?
30 (b) for brown fur
30/50 (total alleles) = 60% frequency for b
11. Describe how a geneticist might be able to tell that this population is evolving.
The allele frequency within the population is changing
12. Can you determine whether an allele is dominant or recessive on the basis of the ratio of
phenotypes in the population? Explain your answer.
No because the phenotypic ratio depends on the allele frequencies of the dominant and
recessive alleles, and the frequency of alleles has nothing to do with whether the allele is
dominant or recessive
13. Read each description below and identify whether it refers to stabilizing, directional, or
disruptive selection.
a. During the Industrial Revolution in England, the peppered moth population became
darker over time as the trees became darker from pollutants. DIRECTIONAL
b. Poison dart frogs appear as either bright orange or bright blue. DISRUPTIVE
c. Most small anole lizards are between 3 and 6 inches long. STABILIZING
14. Why are zebras and horses considered to be members of two different species if they can
interbreed and produce a zorse? In other words, why is the zorse considered to be a hybrid
organism?
The zorse offspring although possible, is not able to reproduce (the zorse is sterile). Because
the zorse cannot pass on its own genetic information it cannot form a new population and
will not evolve.
15. Explain the difference between genetic drift associated with the bottleneck effect and the
founder effect. How does each type of drift affect variation and allele frequencies within the
resulting populations, when compared to the original populations?
Both bottleneck and the founder effect are types of genetic drift (random and small
populations). The bottleneck results from a sweeping change that eliminates the majority of
individuals in the original population (forest fire, flood, earthquake, landslide etc). The
founder effect involves a few members of a population leaving a population and traveling to
a new territory where it starts a new population that may evolve into a separate species
(finches that left south America and inhabited the Galapagos – became Darwin’s 13 species).
Genetic drift would decrease variation (new populations are now smaller) and the allele
frequency could go up or down depending on the alleles of the founding/surviving
individuals that start the new population.
16. A new bee species, which pollinates a particular flower, arises from a larger bee population
that pollinates a different type of flower. Explain why natural selection would favor the
evolution of isolating mechanisms between the two species?
If bees from the two species mated, their offspring might not be able to pollinate either flower
type very well. Isolation mechanisms prevent bees of both species from producing offspring that
are less able to survive in their environment. These mechanisms ensure that offspring have the
adaptions of their parents and help the parents’ alleles to be passed on to future generations.