Biology 11A Chapter 20 - Module Questions

In a population of seahorses, red seahorses on average produce 125 offspring and brown seahorses produce 75 offspring. What is the fitness of the brown phenotype?

0.6

The most fit phenotype is assigned a fitness value of ______.

1

Select the observations that would indicate that a population is deviating from Hardy-Weinberg equilibrium.

Allele frequencies are changing between generations. Genotype frequencies do not match those predicated by the Hardy-Weinberg equation based on existing allele frequencies.

Which evolutionary mechanism changes genotype frequencies but does not change allele frequencies?

Assortive mating

Why does selection occur?

Because some individuals in a population possess more favorable phenotypes than others.

Selection against intermediate-sized beaks in African black-bellied seedcracker finches is an example of which of the following?

Disruptive selection

Which type of selection acts to eliminate individuals which are intermediate on a phenotypic range?

Disruptive selection

Which of the following is true of evolutionary forces in natural populations?

Evolutionary forces can alter allele frequencies in natural populations

What term quantifies reproductive success of a phenotype?

Fitness

Which of the following agents of evolutionary change occurs when alleles move from one population to another?

Gene Flow

Select all of the following processes that can cause changes in allele or genotype frequencies in populations.

Gene flow Mutations Natural selection Nonrandom Mating Genetic drift

How does genetic drift affect allele frequencies?

It changes allele frequencies randomly.

By favoring different phenotypes at different times, oscillating selection acts in which way?

It maintains genetic variation in a population.

Evolutionary change within a population can result from which of the following?

Migration Mutations Natural selection

Select the conditions that must be met for a population to be in Hardy-Weinberg equilibrium.

No new mutations occur. The population is very large. Mating is random.

If we find evidence that a population is experiencing changes in allele frequencies from one generation to the next, we say that this population is which of the following?

Not in Hardy-Weinberg equilibrium

In Northeastern South America, which of the following is the main predator in streams found just below waterfalls?

Pike cichlids

What type of selection affects traits that influence an individual's chances to find a mating partner or be chosen as a mating partner?

Sexual selection

Which type of selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes?

Stabilizing selection

The most fit phenotype produces, on average, which of the following?

The greatest number of surviving offspring

What appears to determine variations in the coloration, size and maturation of guppies in northeastern South American streams?

The location of streams relative to waterfalls

What is gene flow?

The movement of alleles into or out of a population.

What can likely happen to uncommon alleles in small, isolated populations as a result of genetic drift?

They are likely to be lost.

Which describes male guppies located below South American waterfalls where predation is high?

They exhibit drab coloration.

In a laboratory experiment, researchers placed guppies in three different types of pools: no predation, low predation, and high predation. Researchers hypothesized that predation is a selective force and that large, brightly colored guppies are more conspicuous to predators. Based on that, what would you predict the guppies will look like in the pool with high predation after 10 generations?

They should be smaller and not very brightly colored

True or false: Genetic drift, mutations, and nonrandom mating are three agents that can act to produce evolutionary changes in a population.

True

Select all of the following criteria that must be present for natural selection to occur and cause evolutionary change in a population.

Variation must have a genetic basis. Variation must exist among individuals. Variation must result in differences in the number of offspring surviving in the next generation.

The term heterozygote _____ refers to situations in which heterozygotes are more fit then either homozygotes.

advantage

Genetic variation in a population results from evolutionary forces that cause changes in

allele frequencies

When researchers raised guppies in laboratory pools with high levels of predation, the guppies in those aquariums

became smaller and drab in coloration as a result of natural selection after about 10 generations.

Suppose that a population of finches migrates to a small island where most of the seeds are large. On the island, birds with large beaks are more likely to survive, and over time, the mean beak size of the population increases. This is an example of a type of natural selection known as _____ selection.

directional

_____ selection favors individuals at one extreme of a phenotypic range. Those individuals usually have greater reproductive success in a particular environment

directional

In natural populations, most genes

exhibit variation.

Sexual selection influences

fitness. mating success. mate choice.

In _____ - _____ selection, the fitness of a phenotype depends on the proportion of individuals in the population that have that phenotype.

frequency dependent

Evolution can result from any process that changes the _____ composition of a population.

genetic

The processes that lead to evolutionary change are mutations, natural selection, _____ drift, gene flow and _____ mating.

genetic nonrandom

Natural populations exhibit significant phenotypic and _____ variation.

genetic or genotypic

Many 19th century scientists believed that natural selection always favored an optimal form, and therefore would tend to reduce or eliminate which of the following?

genetic variaition

Assortative mating changes ______ frequencies but does not change ______ frequencies.

genotype; allele

Consider a gene with two alleles, A1 and A2. If the fitness of A1A2 individuals is higher than the fitness of both A1A1 and A2A2, we are observing

heterozygote advantage.

According to the theory of blending Inheritance, offspring were expected to be phenotypically _____ relative to their parents, which would dilute any new genetic variants.

intermediate

Hardy-Weinberg equilibrium requires that the population size is _____ and that mating is _____

large random

Changes in allele frequencies within a population may result from _____, which are changes in the nucleotide sequences of an organism's DNA.

mutation

What is the ultimate source of all new alleles?

mutation

When a population is in Hardy-Weinberg equilibrium

no natural selection is occurring.

Ground finches with large bills are favored during times of drought, while ground finches with small bills are favored during times when water is abundant. This is an example of

oscillating selection

_____ selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes.

stabilizing

In frequency-dependent selection

the fitness of a phenotype depends on its frequency in the population.

New mutations are not a major factor affecting the allele frequencies in a population because

the rate at which new mutations occur is low

For a population to be in Hardy-Weinberg equilibrium,

there must be no migration into or out of the population.