Bio Chapter 20A
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?
Assortative mating
Why does selection occur?
Because some individuals in a population possess more favorable phenotypes than others.
What is the founder effect?
Changes in allele frequencies that result from the colonization of a new location by a small group of individuals from a larger population
Sexual selection is a type of natural selection in which the evolution of certain traits is driven by which of the following types of competition?
Competition for mates
Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment?
Directional selection
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
What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium?
Evolutionary forces are affecting the population.
Which of the following is true of evolutionary forces in natural populations?
Evolutionary forces can alter allele frequencies in natural populations
The term heterozygote refers to situations in which heterozygotes are more fit then either homozygotes.
Female choice of males based on certain characteristics
Which of the following is a driving force of intersexual selection?
Female choice of males based on certain characteristics
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
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 variation
How does natural selection affect allele frequencies?
It causes beneficial alleles to become more common. It causes detrimental alleles to become less common.
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.
Which of the following statements about the reproductive strategies of males and females is true?
Males and females often have different reproductive strategies.
Which of the following is true about the reproductive strategies of males and females?
Males are selective in choosing a mate much less frequently than females.
Evolutionary change within a population can result from which of the following?
Migration Mutations Natural selection
Select all of the following processes that can cause changes in allele or genotype frequencies in populations.
Mutations Nonrandom Mating Genetic drift Gene flow Natural selection
Which evolutionary mechanism causes beneficial traits that are heritable to become more common in a population?
Natural selection
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
What is genetic drift?
Random changes in the allele frequencies of a population over time
A deer's antlers, a ram's horns and the bright plumage of a male paradise bird are all examples of which of the following?
Secondary sexual characteristics
In many species of animals, males and females look very different as a result of sexual selection. These animal species exhibit which of the following?
Sexual dimorphism
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
Genetic drift has a greater impact on which of the following?
Small populations
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 is gene flow?
The movement of alleles into or out of a population.
What is fitness?
The relative likelihood that a genotype will contribute to the gene pool of the next generation
Select all of the following criteria that must be present for natural selection to occur and cause evolutionary change in a population.
Variation must result in differences in the number of offspring surviving in the next generation. Variation must exist among individuals. Variation must have a genetic basis.
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
in many animals, selection has favored traits that confer greater ability in mate competition; as a result of such selection, one of the sexes —usually males—can look very different. This is known as sexual---
dimorphism
--- selection favors individuals at one extreme of a phenotypic range. Those individuals usually have greater reproductive success in a particular environment
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 a type of natural selection known as --- selection.
directional
Beaks in African black-bellied seedcracker finches are small or large, but not intermediate in size. This is an example of --- selection.
disruptive
True or false: Within the same species, females and males usually employ the same reproductive strategy.
false
In general, ---are more likely to exhibit mate choice than---
females males
In --- - --- selection, the fitness of a phenotype depends on the proportion of individuals in the population that have that phenotype.
frequancy 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
What evolutionary mechanism results in random changes in allele frequencies from one generation to the next?
genetic drift
Random changes in allele frequencies in small populations are known as---, ---
genetic, drift
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
--- selection is a form of sexual selection based on same-sex competition usually involving males, in which the winner "gains" a mating partner.
intersexual
---selection is a type of natural selection in which competition for mates drives the evolution of certain traits.
intersexual
A type of sexual selection in which members of one sex, usually females, choose mates based on particular characteristics such as courtship songs is called --- ---
intersexual selection
Sexual selection influences
mating success. fitness. mate choice.
----- is the ultimate source of genetic variation
mutation
What is the ultimate source of all new alleles?
mutation
Changes in allele frequencies within a population may result from--- , which are changes in the nucleotide sequences of an organism's DNA.
mutations
The process in which beneficial traits that are heritable become more common in successive generations is called
natural selection
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
Features that increase the chance that a male will be chosen by a female (for example, bright plumage in many male birds) are known as--- --- characteristics.
secondary sexual
The theory of natural -----as a mechanism of evolution was proposed by Charles Darwin.
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.
The change in allele frequencies that occur due to the colonization of a new location by a small group of individuals is called
the founder effect.
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.
