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WorksheetsEvolution Scenarios
Total questions: 10
Worksheet time: 12mins
In most species, scientists have observed that related individuals share about 80% of the same genes. Cheetahs today, however, are known to share 99% of the same genes.
What does this lack of genetic diversity imply about the history of the cheetah population?
Cheetahs never have experienced mutations.
Cheetahs have experienced reproductive isolation and now have a limited number of members with whom to mate.
Cheetahs interbred with other large cat species.
Cheetahs share a common ancestor with other large cat species.
Rabbits were introduced to Australia in the 1800s. They rapidly overpopulated because they had few natural predators in the area. To control their population, scientists introduced a rabbit-specific virus into the population, and their numbers greatly decreased. However, after several generations, the rabbit population began to increase again.
Which statement explains the new increase in the number of rabbits?
The rabbits interbred with native rabbit species.
Some of the rabbits had a natural immunity to the virus.
Some of the rabbits learned to survive even though they were sick.
The rabbits were able to have more offspring by changing their reproductive cycles.
A catastrophic epidemic killed a large proportion of a population of deer in California thereby reducing the gene pool. This is an example of:
directional selection
genetic isolation
the bottleneck effect
the founder principle
The map shows the geographic distribution of salamander subpopulations that descended from the common ancestor E. e. oregonensis. Over millions of years, the salamanders moved south from what is now Oregon and northern California into areas to the east and west of California’s Central Valley.
The salamanders were initially separated by a large lake, and later by the unsuitable habitat of the Central Valley itself. Because of this geographic barrier, gene flow among some of these subpopulations is extremely limited, and in some cases has led to reproductive isolation.
Based on the salamander distribution data shown on the map, choose two salamander subpopulations between which gene flow can occur.
L and M
L and N
N and M
P and L
A researcher conducts an investigation on fiddler crabs to understand the importance of claw size in mating. The male fiddler crabs have one normal-sized claw and one giant claw that they wave to attract female fiddler crabs. The female fiddler crabs have two small, same-sized claws. The researcher places 15 male crabs with different sized claws into an enclosure with conditions similar to those in their natural habitat. The researcher then releases 15 female crabs into the enclosure. The graph shows the percentage of male crabs of different claw size that successfully mated for three successive trials. Select the statement that predict the outcome on the traits of male fiddler crabs in a population over time based on the results of the investigation.
The percentage of males with larger claws will increase in the population.
The percentage of males with smaller claws will increase, as smaller claws are selected for in mating.
The percentage of males with varying claw sizes will remain constant, as both traits are selected for by female crabs.
About 4,500 years ago two cheetah subspecies arose from a common ancestor. The table contains data comparing the two cheetah subspecies. Which subspecies is genetically more closely related to its common ancestor?
A.j. jubatus
A.j. raineyi
Geneticists have determined that the majority of individuals in a small, isolated island population have blood type O. Type A blood is found to be more common in the mainland population from which the island was settled. How could a geneticist best explain the dominance of blood type O in the island population?
Random mutations have occurred in the island population.
Genetic drift has reduced the frequency of type A individuals.
Natural selection has only occurred in the mainland population.
Environmental conditions on the island are less favorable for type O individuals.
A mudslide results in a dramatic reduction in the size of a population. Because the new population does not have the same allele frequencies as the original, this event is referred to as ______.
founder effect
stabilizing effect
diminished effect
bottleneck effect
From an evolutionary perspective, what is the significance of reproductive isolation developing between two populations within a species?
Speciation due to reproductive isolation results in extinction of the ancestral species.
When two populations cannot interbreed, the flow of genetic information between them stops.
Over time, reproductive isolation leads to increasing competition between the populations.
When the size of breeding populations decreases, the mutation rate decreases resulting in greater fitness.
Two subspecies of tufted-ear squirrels have been observed near the Grand Canyon. Scientists believe that these two squirrels evolved from a common population of squirrels that lived in the ponderosa pine forests that once grew in what is now the Grand Canyon. The Kaibab squirrel is found on the north side of the canyon, and the Abert’s squirrel is found on the south side of the canyon. The canyon is too wide for the squirrels one either side to cross.
Similar selection pressures on each side of the canyon caused fur color mutations to occur in the two populations.
As the canyon formed and the ponderosa forests disappeared, the original population was split into two isolated populations that could no longer share genes through mating.
The original population was able to find similar habitats in many small pockets of connected forests remaining around the Grand Canyon.
Natural land bridges connecting the two sides of the canyon allowed gene flow to occur between the populations after the ponderosa forests disappeared.
