10.3 Gene Pools and Speciation

A hunter tends to kill the bigger individuals of a population for their meat or for large ornamental trophies. Therefore, the population tends to have more individuals who are smaller. What is this an example of?

• A. Directional selection

• B. Disruptive selection

• C. Natural selection

• D. Stabilizing selection

Natural selection can operate in different ways. What is the effect of disruptive selection?

• A. It eliminates individuals with intermediate forms of a characteristic.

• B. It eliminates individuals at random regardless of their characteristics.

• C. It favours individuals with intermediate forms of a characteristic.

• D. It favours individuals at one extreme of the range of variation in a characteristic.

The cheetah (Acinonyx jubatus) is a large cat found in Africa. It has been discovered that organs could be transferred between any two individuals without rejection of the organ.

What is the probable reason for this?

• A. Cheetahs have poor reproductive success.

• B. Cheetahs have high heterozygosity

• C. Cheetahs have a large gene pool.

• D. Cheetahs have a small gene pool.

Which example shows disruptive selection?

• A. Giraffe necks have become longer over time.

• B. Medium-sized beaks in hummingbirds have decreased in frequency over time.

• C. The peppered moth became less common in polluted environments.

• D. Human babies with a very high or a very low birth mass have a higher mortality rate.

What can lead to reproductive isolation after just one generation?

• A. Polyploidy

• B. Increased mutation rate

• C. Changed allele frequencies

• D. Independent assortment of chromosomes

The graph shows variations in beak size for the bird Geospiza fortis on an island in the Galápagos archipelago.

What evidence from the graph indicates that disruptive selection is occurring?

• A. An intermediate beak size is less common.

• B. Median beak size is the most common.

• C. Smaller beaks are favoured.

• D. Larger beaks are favoured.

Fossil records show that black bears increased in size during the Ice Age and decreased in size with warmer temperatures. What type of selection do these changes in size represent?

• A. Allopatric

• B. Directional

• C. Disruptive

• D. Stabilizing