Chapter 21 - Microevolution

Question 0

What is phenotypic variation?

Answer 0

Differences in appearance or function between individual organisms.

Question 1

What is microevolution?

Answer 1

It is the small-scale genetic changes that populations undergo, oftenn in response to shifting environmental circumstances.

Question 2

What is quantitative variation?

Answer 2

Variation that is measured on a continuum (such as height) rather than in discrete units or categories.

Question 3

What is qualitative variation?

Answer 3

Variation that exists in two or more discrete states, with intermediate forms often being absent.

Question 4

What is polymorphism?

Answer 4

The existence of discrete variants of a character among individuals in a population.

Question 5

What are genotype frequencies?

Answer 5

The percentage of individuals in a population possessing a particular genotype.

Question 6

What are allele frequencies?

Answer 6

The abundance of one allele relative to others at the same gene locus in individuals of a population.

Question 7

What is the Hardy-Weinberg principle?

Answer 7

An evolutionary rule of thumb that specifies the conditions under which a population of diploid organisms achieves genetic equilibrium.

Question 8

What is genetic equilibrium?

Answer 8

The point at which neither the allele frequencies nor the genotype frequencies in a population change in succeeding generations. It also identifies the conditions under which evolution will not occur.

Question 9

What is mutation?

Answer 9

Heritable change in DNA. It introduces new genetic variation into the populations and doesn’t change allele frequencies quickly.

Question 10

What is gene flow?

Answer 10

Change in allele frequencies as individuals join a population and reproduce. May introduce genetic variation from another population.

Question 11

What is genetic drift?

Answer 11

Random changes in allele frequencies caused by chance events. Reduces genetic variation, especially in small populations. Can eliminate rare alleles.

Question 12

What is natural selection?

Answer 12

Differential survivorship or reproduction of individuals with different genotypes. One allele can then replace another or allelic variation can be preserved.

Question 13

What is nonrandom mating?

Answer 13

Choice of mates based on their phenotypes and genotypes. Doesn’t directly affect allele frequencies, but usually prevents genetic equilibrium.

Question 14

What is population bottleneck?

Answer 14

An evolutionary event that occurs when a stressful factor reduces population size greatly and eliminates some alleles from a population. It greatly reduces genetic variation.

Question 15

What is the founder effect?

Answer 15

An evolutionary phenomenon in which a population that was established by just a few colonizing individuals has only a fraction of the genetic diversity seen in the population from which it was derived. Rare alleles occur in higher frequencies.

Question 16

What is relative fitness?

Answer 16

The number of surviving offspring that an individual produces compared with the number left by others in the population. Thus, a particular allele will increase in frequency in the next generation if individuals carrying that allele leave more offspring than individuals carrying other alleles.

Question 17

What is directional selection?

Answer 17

A type of selection in which individuals near one end of the phenotypic spectrum have the highest relative fitness. The extremes are favored, which means the mean value becomes higher or lower. Variability may be reduced.

Question 18

What is stabilizing selection?

Answer 18

A type of natural selection in which individuals expressing intermediate phenotypes have the highest relative fitness. The extremes are eliminated, which reduces genetic and phenotypic variation.

Question 19

What is disruptive selection?

Answer 19

A type of natural selection in which extreme phenotypes have higher relative fitness than intermediate phenotypes. As a result, polymorphism is promoted.

Question 20

What is balanced polymorphism?

Answer 20

The maintenance of two or more phenotypes in fairly stable proportions over many generations.

Question 21

What is heterozygote advantage?

Answer 21

Individuals that are heterozygous have higher relative fitness than either homozygote. This maintains balanced polymorphism.

Question 22

What is frequency-dependent selection?

Answer 22

A form of natural selection in which rare phenotypes have a selective advantage simply because they’re rare.

Question 23

What is the neutral variation hypothesis?

Answer 23

Some variation at gene loci coding for enzymes and other soluble proteins is neither favored nor eliminated for natural selection. It explains why there are different levels of genetic variation in different populations.

Question 24

What is an adaptive trait?

Answer 24

Any product of natural selection that increases the relative fitness of an organism in its environment.

Question 25

What is adaptation?

Answer 25

The accumulation of adaptive traits over time.