Natural Selection and Genetic Variation

The video tutorial covers chapter 17, focusing on evolution and genetic variation within populations. It explains the concept of a gene pool and the sources of genetic variation, such as mutations and gene shuffling. The tutorial discusses natural selection's impact on allele frequencies and evolution, using examples like lizards and giraffes. It also explores polygenic traits and the types of natural selection: directional, stabilizing, and disruptive. The video concludes with a brief mention of genetic drift, to be covered in the next video.

What is a gene pool?

• A set of genes that do not change over time

• A group of individuals of different species

• A pool where genes are stored

• A collection of all the alleles in a species

Which of the following is a source of genetic variation?

• Gene elimination

• Gene deletion

• Gene shuffling

• Gene fixation

What is an example of a single-gene trait?

• Height in humans

• Widow's peak

• Eye color

• Skin color

How does a polygenic trait differ from a single-gene trait?

• It does not affect phenotypes

• It is not influenced by the environment

• It is controlled by multiple genes

• It is controlled by one gene

What can natural selection lead to in a population?

• Stability of all traits

• Elimination of all mutations

• Increased genetic diversity

• Changes in allele frequencies

In the lizard example, why might black lizards become more common?

• They reproduce less

• They are less visible to predators

• They absorb heat faster

• They are more colorful

What is directional selection?

• Selection that shifts the average trait

• Selection that favors extreme traits

• Selection that eliminates all traits

• Selection that favors average traits

Which type of selection favors the average form of a trait?

• Random selection

• Disruptive selection

• Stabilizing selection

• Directional selection

What happens in disruptive selection?

• Only one trait is favored

• The average trait is favored

• The population splits into two extremes

• All traits are eliminated

Why might predators avoid certain caterpillars in disruptive selection?

• They are not visible

• They are too fast to catch

• They mimic poisonous species

• They are too small to eat