Natural Selection

A population of small fish lives in a lake with a sandy bottom. Large shore birds prey on these fish. Although most of the fish are the same light brown color as the sandy lake bottom, about 10% are mottled. A construction company begins dumping loads of gravel in the bottom of the lake, giving it a mottled appearance. Which outcome would you predict?

The proportion of mottled fish in this population will increase over time.

Small lizards have difficulty defending their territory, but large lizards are more likely to be preyed upon by owls. Which type of selection would act on body size in these lizards under these conditions?

Stabilizing selection

Why do dark-colored rock pocket mice on dark lava flows have white bellies?

There is no selection for dark bellies by visual predators.

Why did dark-colored rock pocket mice first appear in a population of light-colored rock pocket mice?

They have a genetic mutation that affects their fur color

Natural selection can be defined as ________.

a process in which organisms with certain inherited traits are more likely to survive and reproduce than individuals with other traits

In the Hardy-Weinberg formula, what does 2pq represent?

frequency of heterozygotes

The total collection of alleles in a population at any one time makes up that population's ________.

gene pool

A change in the gene pool due to chance results in ________.

genetic drift

In sexual selection, individuals with certain inherited characteristics are more likely to obtain mates than other individuals. This often results in __________, differences between the sexes in size, appearance, and behavior.

sexual dimorphism

Which situation is most likely to decrease genetic variation?

stabilizing selection

The population of American bison used to number in the millions. Hunting and other problems greatly decreased the number of bison to about 1,000. Today, the numbers are recovering to estimates of more than 200,000 bison. This crash in the population of bison and recent recovery is an example of __________.

the bottleneck effect

selective pressure

when the environment pushes an individual or population to adapt or evolve

________ believed that species are fixed forms that do not change over time while ________ believed that evolution is the refinement of traits that equip organisms to perform successfully in their environments.

Aristotle; Lamarck

In a species of snail, dark-shelled individuals are better hidden from bird predators in the shady forest, while light-shelled individuals are better hidden in well-lit brushy edge areas. If there were no areas of intermediate brightness in this habitat,which type of selection would act on shell color in these snails?

Disruptive selection

In the lab, Nachman examined dark mice from two different populations living hundreds of miles apart. The mice looked nearly identical. Their dark color was caused by two different genes. What does this tell you?

Two completely different mutations in two separate genes can generate the same phenotype. Dark fur color evolved independently on each lava flow. There are at least two genes involved in creating dark mouse fur. Under very similar conditions, natural selection can favor very similar adaptations.

Disruptive selection

_______ favors phenotypes at both ends of a range over intermediate phenotypes. This type of selection may occur when the habitat is varied.

Directional selection

_________ favors phenotypes at one end of a range and is common in periods of environmental change.

Mutations are always __________.

a change in an individual's DNA

Natural selection generally results in ________.

a population that is adapted to its current environment

Homology is evidence of ________.

common ancestry

The wing of a bat is homologous to the _____ of a whale.

flipper

The founder effect differs from a population bottleneck in that the founder effect ________.

involves the isolation of a small colony of individuals from a larger population

In a type of sexual selection often called _______, individuals of one sex (usually females) are choosy in selecting their mates. This choice is often based on the showy appearance or behavior of the male.

mate choice

The original source of genetic variation that serves as the raw material for evolution is ________.

mutation

genetic drift

random change in allele frequencies that occurs in small populations

What does evolutionary fitness measure?

relative reproductive success

Which statement about the voyage of the Beagle is TRUE?

It turned into a tremendous opportunity for Darwin to collect fossils, plants, and animals.

gene flow

Movement of alleles into or out of a population due to the migration of individuals to or from the population

The common house mouse species, Mus musculus, has the following taxonomic classification: Mus, Muridae, Rodentia, Mammalia, Chordata, Animalia, Eukarya. Which part of the name is the Family?

Muridae

What does Dr. Carroll mean when he says, "while mutation is random, natural selection is not"?

Natural selection favors some mutations. Natural selection acts on traits. Mutations for advantageous traits are more likely to be passed on to the next generation.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Which statement is TRUE?

Natural selection works on variation already present in a population.

_________favors intermediate phenotypes, selecting against phenotypes at both ends of a range and reducing variation.

Stabilizing selection

Which phenomenon (or lack of) will prevent significant genetic drift?

The population size is large.

After surviving a bottleneck, a population recovers to the point where it consists of as many individuals as it did prior to the bottleneck. Which statement is most likely to apply to this population?

The post-bottleneck population exhibits less genetic variation than the pre-bottleneck population.

Part complete When dark-colored fur gives mice a 1% competitive advantage and 1% of the population begins with dark fur, in about 1000 years, 95% of the population will have dark fur. Which of the following statements is true?

If dark-colored rock pocket mice had a competitive advantage of 0.1%, it would take longer for 95% of the population to have dark fur.

Which of the following events could NOT be caused by a population bottleneck?

Increased population size

Which of the following statements about the amoeba population described at the end of the tutorial is true?

It is more vulnerable to extinction due to lack of genetic variation.

Which situation is an example of sexual selection?

Peahens choose to mate with peacocks that have the brightest tails.

According to current evolutionary theory, which of the following is true?

Populations are the units of evolution.