Unit 7 Evolution

Birth weight averages between 6 to 8 pounds. Which type of selection describes birth weight of humans?

• Directional

• Disruptive

• Sexual

• Stabilizing

Answer explanation

The frequency of birth weights have maintained between 6 to 8 pounds. Since the weight has stabilized to the intermediate phenotype, this is STABILIZING selection.

If looking for a recent ancestor of the fish, look at

• V

• X

• Y

• Z

Answer explanation

The fish is in layer W. The V would be a descendant while the X, Y, & Z would be ancestors. The most recent would be the one right before layer W which is X.

Peppered moths are an example of artificial selection.

• True

• False

Answer explanation

Peppered moths are an example used in many classrooms. During the industrial revolution, humans caused the increase of smog and soot in the air which darkened the trees of the peppered moths’ habitat. Over many generations, it was observed that the moths underwent directional selection to a darker moth phenotype.

Although humans caused the selective pressure which led to the directional selection, nature still determined reproductive fitness of the phenotypes.

Extremely large population attempts to avoid

• Gene flow

• Genetic drift

• Mutations

Answer explanation

Genetic drift involves the change of allele frequencies due to random chance.

For Hardy-Weinberg, condition for gene flow?

• No gene flow

• Yes gene flow

Answer explanation

Hardy-Weinberg states that a population is not evolving if the allele frequencies stay the same. When the individuals immigrate or emigrate, alleles are added or removed from the population, which changes the allele frequency. The five conditions for Hardy-Weinberg are LARGE population size, RANDOM mating, NO mutations, NO gene flow, and NO natural selection.

What is genotype frequency?

• The number of individuals with each genotype in the population

• The number of individuals with each phenotype in the population

• The percent of individuals with each genotype

• The percent of individuals with each phenotype

Answer explanation

Frequencies refer to percents, so the genotypic frequency is the percent of the genotype in the population. It is calculated as p², 2pq, or q² in the Hardy-Weinberg equilibrium formula. It can be calculated as number of genotype divided by the total individuals.

Which of the following evolves?

• Individuals

• Populations

Answer explanation

Individuals are selected for or against based on their phenotypic characters. That selection causes certain phenotypes to be more likely to survive and thus the frequency of the trait in the population will change. This means that the population has evolved not the individuals.

What does it mean if the population remains in Hardy Weinberg equilibrium?

• Population is not evolving

• Population is genetically diverse

• Population is undergoing gradual equilibrium

• Population is undergoing punctuated equilibrium

Answer explanation

Hardy-Weinberg equilibrium states the conditions that must be met so the genetic frequencies remain the same and the population is not evolving.

Which population is better to overcome genetic drift?

(as in for genetic drift to not have an affect on the allele frequency)

• Small

• Large

Answer explanation

Genetic drift involves random event changes in the allele frequency. If the population is larger, a random event like a flood will not change the allele frequency as much.

An individual evolves to better match its environment.

• True

• False

Answer explanation

Individuals DO NOT evolve.

Populations evolve.

The individuals are selected for or against, but the population will change due to those selections.