Chapter 5: The Genetical Theory of Natural Selection

Historical contingency

Historical contingency

________ is the outcome of evolution that is determined by where the population begins.

Selective sweeps

________ are situations in which a beneficial mutation spreads through a population.

Standing genetic variation

_________ is when an allele that is present in the population is initially not favored, but then suddenly becomes beneficial when conditions change.

beneficial allele

When a(n) ________ spreads by selection, the final outcome is that it becomes fixed (it reaches a frequency of 1).

evolutionary trade-off

When there is a(n) _________, natural selection favors the allele that has the highest fitness overall.

W

{answer is the variable}= (probability that the individual survives to maturity)* (expected number of offspring if the individual does survive)

strength of selection

The ________ is determined by fitness differences.

positive selection

The rate at which ________ causes an allele frequency to evolve depends on dominance.

2

A(n) individual who leaves 2 offspring has a fitness of __[number]____.

positive frequency dependence

When frequency-dependent selection favors the most common allele, this is called ___________.

deleterious alleles

Balancing selection is fundamentally different from the selection on beneficial and ________, which acts to remove genetic variation.

Relative fitnesses

________ play a critical role in determining the speed and outcome of evolution by natural selection.

Multiple niche polymorphism

________ is when different genotypes specialize in different ecological niches.

Genetic correlations

________ occur when two traits tend to be inherited together.

adaptive landscape

The ________ is a plot created by Wright that tells us how the population will evolve.

absolute fitness

A(n) individual's ________ is the number of zygotes (offspring) produced over its lifetime.

dominant

A(n) allele is _____ if it causes the same phenotypic effect when heterozygous as when homozygous.

Deleterious mutations

________ are mutations that decrease fitness.

Fitness components

________ are one of several events in the life cycle of many organisms that contributes to the determination of fitness, such as survival to maturity, mating success, and fecundity.

genetic variance

The increase in mean fitness per generation is equal to the ________ for fitness itself.

Overdominance

________ occurs when the heterozygote has higher fitness than both homozygotes.

Natural selection

________ causes populations to evolve so that they become better adapted to their environment: the average survival and reproduction of individuals increase through time.

Positive selection

________ ultimately eliminates genetic variation, so other evolutionary factors must be responsible for maintaining all the genetic variation in nature.

genetic variation

Balancing selection preserves ________, and in most cases, the population will evolve to the same allele frequency no matter where it begins.

Positive selection

________ is the selection for an allele that increases fitness.