Chapter 23 Mastering Biology Flashcards

What is true of microevolution?

It is evolution that involves only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype.

It is evolution that influences only a small subset of the populations that comprise a species.

It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations.

It is evolution that is restricted to individual organisms.

It is evolution that results in the origin of small numbers of new species.

One of the following is NOT a source of genetic variation.

genetic drift
mutation
sexual reproduction
alteration of gene number or position
rapid reproduction

The original source of all genetic variation is _____.

natural selection
independent assortment
sexual reproduction
mutation
recombination

Microevolutions occur when ________.

changes in allele frequencies in a population occur over generations
gene flow evenly transfers alleles between populations
a bird has a beak of a particular size that does not grow larger during a drought
individuals within all species vary in their phenotypic traits

Which statement about variation is true?

All genetic variation produces phenotypic variation.
All new alleles are the result of nucleotide variability.
All phenotypic variation is the result of genotypic variation.
All nucleotide variability results in neutral variation.

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

Each bird evolved a deeper, stronger beak as the drought persisted.
The frequency of the strong-beak alleles increased in each bird as the drought persisted.
Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation.
Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.

Genetic variation ________.

is created by the direct action of natural selection
must be present in a population before natural selection can act upon the population
arises in response to changes in the environment
tends to be reduced when diploid organisms produce gametes

Which of the following are basic components of the Hardy–Weinberg model?

Allele frequencies, number of individuals in the population
Allele frequencies in a subset of the population
Allele frequencies, phenotype frequencies
Frequencies of two alleles in a gene pool before and after many random matings

Which of the following evolutionary forces consistently results in adaptive changes in allele frequencies?

Inbreeding
Mutation
Selection
There is no evolutionary force that results in adaptive changes in allele frequencies.

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.

sexual reproduction
genetic drift
sexual selection
immigration
mutation

Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg equilibrium for this gene, what percentage of the population must be heterozygous for this trait?

40%
48%
32%
16%

Which Hardy-Weinberg condition is affected by population size?

selection
gene flow
no mutation
genetic drift

Which one of the following conditions would allow gene frequencies to change by chance?

gene flow
small populations
mutation
large population

The higher the proportion of loci that are "fixed" in a population, the lower are that population's ________.

nucleotide variability and average heterozygosity
average heterozygosity
chromosome number
nucleotide variability

In the formula for determining a populations genotype frequencies, the "pq" in the term 2pq is necessary because _____.

heterozygotes can come about in two ways
heterozygotes have two alleles
the population is diploid
the population is doubling in number

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

0.36
0.64
0.75
0.80

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.

What is the estimated frequency of allele A in the gene pool?

0.125
0.50
0.25
0.75

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

mutation
nucleotide variability
gene flow
founder effect
bottleneck effect

Soon after the island of Hawaii rose above the sea surface (somewhat less than one million years ago), the evolution of life on this new island should have been most strongly influenced by ________.

habitat differentiation
a genetic bottleneck
sexual selection
the founder effect

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population?

population bottleneck and Hardy-Weinberg equilibrium
founder effect and genetic drift
heterozygote advantage and stabilizing selection
mutation and natural selection

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident?

Mutation caused genetic drift and decreased fitness.
Mutation caused the fixation of new alleles.
Mutation led to increased genetic variation.
Mutations caused major changes in rodent physiology over time.

What is the only evolutionary mechanism that consistently leads to adaptive evolution? See Concept 23.4 (Page 495)

neutral variation
genetic drift
the bottleneck effect
gene flow
natural selection

How does diploidy help to preserve genetic variation?

It fosters the exchange of genes between different populations.
It restricts the gene pool by chance events such as floods or other catastrophic events.
It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes.
It allows the frequency of a recessive allele in a population to be predicted under certain conditions.
It helps individual organisms make a greater contribution to the gene pool of the next generation.

Arrange the following in order from most general to most specific.
1 natural selection
2. microevolution
3. intrasexual selection
4. evolution
5. sexual selection

4, 2, 1, 5, 3
1, 4, 2, 5, 3
4, 1, 2, 3, 5
4, 2, 1, 3, 5