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Evolution Review Questions
SBI 3U1
Thinking and Investigation Questions
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Explain why extinct species are not equally represented in the fossil record. What might improve an
organism’s chances of leaving fossil evidence?
Explain why the evolutionary cost of failing to mate is extreme.
What role does stabilizing selection have on a population when the environment is not changing? Explain
in terms of the selective pressure on mutations that might occur.
Relate, with an example, how random chance can have a greater effect on small populations than on
larger populations.
Describe some of the many reproductive isolating mechanisms that might prevent Canada geese from
successfully reproducing with penguins on the Galapagos Islands.
Provide three examples for each of the following:
(a) directional selection
(b) stabilizing selection
(c) disruptive selection
(d) sexual selection
Examine the figure on the right. Add relevant labels. Write a
description of the effect this diagram illustrates.
Identify the type of selection (disruptive, stabilizing, directional,
sexual, runaway, or cumulative) operating in these examples:
(a) diversity among honey creepers
(b) a peacock’s tail
(c) the central nervous system
(d) egg size in robins
(e) body size in the blue whale
(f) the courtship dance of the blue-footed booby
Would you expect bacteria occurring in wildlife, or in domesticated animals, to show signs of antibiotic
resistance? Explain your answer.
Define evolution in terms of gene frequencies.
A small population of pygmy mammoth measuring only 2 m in height once lived on a small island off the
coast of California. Biologists believe this is an example of a population that descended from a few large
mammoth that reached the island more than 50 000 years ago. Explain how the small founding
population, remote location, and natural selection on this island might have each contributed to the
formation of this unusual species.
In a population of 40 000 bats, you have identified two distinct phenotypes that result from two alleles at
a single gene locus. One allele (C) produces dark brown hair and the other (c) produces cinnamoncoloured hair. If only 16 bats are cinnamon-coloured, estimate the allele frequencies in the population.
Assume the population is in Hardy–Weinberg equilibrium. Approximately how many bats would you
expect to be heterozygous for this hair colour trait?
Compare and contrast allopatric speciation when two populations are isolated from each other on
separate large and ecologically distinct islands, and on separate large and ecologically similar islands.
Regarding extinction in the geologic record:
(a) What evidence exists that Earth’s history has included a number of mass extinction events? What
evidence offers clues to the cause(s) of these extinctions?
(b) Mass extinction events are followed almost immediately by periods of very rapid speciation.
Explain this observation.
15. In courtship, male scorpion flies (Panorpa latipennis) offer females gifts of dead prey. Females feed on
these gifts during mating and copulate longer with those males that offer the largest gifts. How might the
size of the gift indicate to females that the male is a better mate?
16. What are considered to be the most significant adaptations that distinguish humans from chimpanzees?
17. Look at the hominoid phylogeny below. Mark locations that correspond to:
(a) the most recent common ancestor that present-day humans share with Australopithecus boisei;
(b) the most recent common ancestor of both humans and chimpanzees;
(c) a possible position at which a species began to use relatively complex tools;
(d) a possible position at which the fusion mutation that resulted in the creation of human
chromosome 2 might have occurred.
18. If the multiregional hypothesis regarding human origins were correct,
(a) what fossil evidence might one expect to find outside Africa?
(b) why would geneticists expect to see greater genetic diversity in non-African populations than
they have so far?
Application Questions
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In what way do cosmetics and clothing companies take advantage of evolutionary mechanisms to market
and sell their products?
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In many zoos, artificial insemination of female tigers is becoming common practice. Semen may be
collected from male tigers in various zoos around the world, frozen in liquid nitrogen, and shipped to zoos
where it is used to inseminate female tigers in estrus.
(a) Why do you think this is being done?
(b) How might this affect the gene pool of tiger populations?
(c) Do you think these efforts are enough to prevent a genetic bottleneck from occurring? Explain.
(d) What conditions do you think are necessary to ensure the genetic diversity of zoo populations?
3.
The majority of the Afrikaner population in South Africa is descended from a single shipload of Dutch
immigrants in 1652. Compared to the Dutch population, these descendants have a much higher incidence
of such rare genes as the ones that cause Huntington’s disease and the enzyme defect called variegate
porphyria. What is the most likely explanation for this observation?
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Consider the cladogram on the right. It was developed
based on DNA sequence data for the gene encoding a
milk protein.
(a) What is an outgroup? Suggest an example of
an outgroup for this cladogram.
(b) Which group is more closely related to the
pig: cows or whales? Explain.
(c) If the cow and whale share a common
mutation in the gene for this milk protein,
which other group(s) must also have the
same mutation? Explain.
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Although evidence shows a very close evolutionary relationship between humans and chimpanzees,
humans do exhibit marked differences in mental and physical attributes. How might bipedalism have
influenced the success of humans as toolmakers? How might this same trait be related to the long period
of infant dependency unique to humans?
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As the rapid pace of fossil discoveries continues, new members are being added to the human family tree.
In 2001, palaeontologists reported the discovery of what they believe to be a new species of early
hominid. The species, named Kenyanthropus platyops, is 3.5 million years old. In 2003, paleontologists
reported the discovery of a new member of the genus Homo. The species, Homo floresiensis was
discovered on the island of Flores in Indonesia. Find out more about these fossil forms and revise the
hominoid family tree (on the previous page) based on the latest reported fossil evidence.