population genetics

Blank 1: oscillating Blank 2: genetic

A type of natural selection called _____ selection favors different phenotypes at different times and maintains ______ variation in populations.

studies of the guppy Poecilia reticulata.

An example of recent experiments of evolution that have been conducted both in the lab and in the field are

Mating success Individual survival Production of viable, numerous offspring

Choose all the components of fitness from the list below:

Its frequency will remain unchanged

Consider a gene with two alleles, one dominant, and the other recessive. If this population is in Hardy-Weinberg equilibrium with respect to this gene, what would happen to the dominant allele from generation to generation?

gene flow opposing natural selection.

Consider two populations of the same plant species - population A and population B and the gene Xx. Researchers discover that there is constant flow of the x allele from population B into population A. This allele happens to be detrimental to individuals in population A because of the local soil conditions. This is an example of

acts to eliminate one extreme from a range of phenotypes.

Directional selection

Gene flow can spread a beneficial allele or an inferior allele from one population to other populations.

Gene flow can sometimes promote evolutionary change, but at other times it can constrain evolutionary change. How is that possible?

reduce evolutionary change. remove alleles from a population. introduce new alleles to a population. promote evolutionary change.

Gene flow may

Conduct controlled experiments

How could scientists determine conclusively if natural selection versus genetic drift, the environment, or some other cause was responsible for the differences seen in guppies above and below South American waterfalls?

0.48

If the frequency of heterozygotes in a population of mice is 0.48 for a particular gene, what would be the frequency of heterozygotes in future generations if the population is in Hardy-Weinberg equilibrium?

Not in Hardy-Weinberg equilibrium

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?

exhibit variation.

In natural populations, most genes

not high enough

In nature, mutation rates are usually ______ to maintain alleles that are not favored in a population by natural selection.

even if the alleles are not favored by natural selection.

In theory, if mutation rates were high enough, alleles could be maintained in a population

Genetic variation

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?

more than one gene.

Most phenotypes in nature are affected by

genes

Multiple _____are usually responsible for most traits.

at a very slow pace Reason: Darwin thought that evolution always occurred very slowly. Recently, many examples of very rapid evolution have been described.

Recent evolutionary studies have shown that Darwin was mistaken in his belief that evolution occurred ____.

interactions between genes pleiotropy lack of genetic variation

Select all of the following factors that limit what selection can accomplish.

Natural selection Nonrandom Mating Mutations Gene flow Genetic drift

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

Evolutionary forces can act together to change allele frequencies. Evolutionary forces can work in opposition to change allele frequencies.

Select all of the following that are true about maintaining genetic variation in populations.

Natural selection The founder effect Differences in nutrition

Select all of the following that could account for the morphological differences observed in male guppy populations above and below waterfalls in South America.

Scientists thought that selection should always favor an optimal form. Genetic variants were expected to be diluted to the point of disappearing in future generations. Segregation of alleles among progeny of hybrids was not understood.

Select reasons why genetic variation within natural populations was a puzzle to Darwin and other scientists in the 19th century.

Genetically similar individuals preferentially mate with each other.

Select the statement that describes nonrandom mating.

directional

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 _______ selection.

evolution.

The accumulation of differences in species that causes new species to arise from existing ones is a process called

significant.

The amount of genetic variation present in naturally occurring populations is

natural selection.

The guppy, which lives in streams above and below waterfalls in northeastern South America, has been the subject of recent lab and field studies demonstrating

The greatest number of surviving offspring

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

natural selection

The process in which beneficial traits that are heritable become more common in successive generations is called ____

selection

The theory of natural________ as a mechanism of evolution was proposed by Charles Darwin.

evolution

The word ______ is used to refer to how an entity, such as a species, changes over time.

true Reason: There are five agents (they match the five assumptions of HWE) that can bring about evolution in populations - mutations, gene flow, genetic drift, non-random mating and natural selection.

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

b. Evolutionary forces are affecting the population.

What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium? a. Allele frequencies are stable from one generation to the next. b. Evolutionary forces are affecting the population. c. The population is isolated from other populations of the same species. d. Genotype frequencies but not phenotype frequencies are the same from one generation to the next.

Genetic drift

What evolutionary mechanism results in random changes in allele frequencies from one generation to the next?

Nonrandom mating

What evolutionary process is occurring if individuals with certain genotypes mate with each other more commonly than would be expected on a random basis?

The relative likelihood that a phenotype will produce the most offspring

What is fitness?

The movement of alleles into or out of a population.

What is gene flow?

Random changes in the allele frequencies of a population over time

What is genetic drift?

Mutation

What is the ultimate source of all new alleles?

it has higher fitness than either homozygote

When heterozygous advantage exists, how would you describe the fitness of the heterozygous genotype?

Heterozygote advantage

Which term describes a situation in which organisms with two different alleles at a particular loci are favored and maintained within a population?

Directional selection

Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment?

Stabilizing selection

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

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

Why does selection occur?

mutation

________is the ultimate source of genetic variation.

Stabilizing

_____selection acts to prevent change away from an already common intermediate phenotype.

It maintains genetic variation in a population.

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