MasteringBiology Questions

Which type of selection tends to increase genetic variation?

Disruptive selection eliminates phenotypes near the ____ and favors the _____ phenotypes, resulting in ____ in a population

In a bell-shaped curve, the x-axis of the graph represents which of the following?

Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?

Directional selection drives the average of the population _____

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?

Stabilizing selection causes _____; ____ phenotypes become less common

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?

Disruptive selection causes ____ to be favored over the intermediate phenotypes

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?

Allele frequencies measure _____

By looking at how allele frequencies change over time, ____

Consistently causes a population to become better adapted to its environment

Cannot cause a harmful allele to become more common

A result of differential success in reproduction

Responsible for the founder effect

Causes allele frequencies to fluctuate randomly

Responsible for the bottleneck effect

A result of the movement of fertile individuals or their gametes

Can introduce new alleles into a population's gene pool

Natural selection is the result of ____

Natural selection is the only mechanism of evolution that ____

Genetic drift describes evolution due to _____ and causes _____ fluctuations in allele frequencies.

Genetic drift can have a _____ effect in a small population

Gene flow results when _____.

Gene flow can bring new alleles that are ____, ____, or ___ into a population

During an extreme heat wave, plants with white flowers survive better. Mechanism? Effect on allele frequencies?

A person uproots the five closest plants, which all happen to have white flowers. Mechanism? Effect on allele frequencies?

A storm kills many plants at random. Mechanism? Effect on allele frequencies?

Plants with purple flowers attract more insects, which pollinate the plants. Mechanism? Effect on allele frequencies?

Workers from a nearby greenhouse accidentally introduce white flower seeds into this population's habitat. Mechanism? Effect on allele frequencies?

Different events and conditions result in _____, _____, and ____

Natural selection, genetic drift, and gene flow cause _____ in different ways

_____, which results from differential survival and reproduction, is the only mechanism of evolution that consistently causes a population to become better adapted to its environment.

_____ and _____ cause alleles to increase in frequency regardless of whether they are harmful, neutral, or beneficial, _____ causes only beneficial alleles to become more common in a population