Biology Chapter 23 Review

Gene Flow

-a result of the movement of fertile individuals or their gametes -can introduce new alleles into a population's gene pool

Genetic Drift

-can result from the bottleneck effect and the founder effect -causes allele frequencies to fluctuate randomly

Natural Selection

-consistently causes a population to become better adapted to its environment -a result of differential success in reproduction -cannot cause a harmful allele to become more common

Which of the following are causes of evolutionary change?

-genetic drift -gene flow -natural selection -mutation

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

0.4

If gene flow into a population introduces a ___, fitness will ___; but if gene flow introduces a ___, fitness will ___.

1. beneficial allele 2. go up 3. deleterious allele 4. go down

Marrying close relatives is a form of ___ that would have increased the ___ of ___ alleles.

1. inbreeding 2. homozygosity 3. recessive

If ___ palm seeds have higher fitness than ___ palm seeds (in the presence of toucans), then the fitness of palms will ___ over time in the absence of toucans because large seeds ___ be dispersed and will have ___ chance of survival.

1. larger 2. smaller 3. decrease 4. will no longer 5. a lower

Which mode of natural selection is most likely to contribute to speciation?

Disruptive selection

Which type of selection tends to increase genetic variation?

Disruptive selection

Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population. (T/F)

False

Suppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

For the species in which the males never help raise offspring, the fundamental asymmetry of sex is pronounced and sexual dimorphism should be higher than for species in which males always help raise offspring.

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

Frequencies of 2 alleles in a gene pool before and after many random matings

Select the correct statement about gene flow

Gene flow makes allele frequencies more similar between populations.

Predict the change of allele frequencies in a small population of sea turtles over time due to inbreeding alone versus inbreeding plus natural selection. Assume the gene that causes albinism has the starting allele frequencies A = 0.99 and a = 0.01, where only aa individuals are white.

If inbreeding alone occurs, the genotype frequencies would change (AA and aa would become more common, Aa less common) but the allele frequencies would remain A = 0.99 and a = 0.01. However, if inbreeding plus natural selection occurs, then the frequency of the a allele likely will decrease in the population (and the frequency of A will increase), since the white sea turtles are easier for predators to find.

Select the example of intersexual selection.

Male zebra finches with more brightly colored beaks have greater reproductive success.

Which evolutionary mechanism increases genetic variation in a population?

Mutation

Which of the following evolutionary forces could create new genetic information in a population?

Mutation

Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.

Mutations do not occur because an organism wants or needs them. They just happen randomly and can be beneficial, neutral, or deleterious.

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

Selection

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?

Stabilizing selection

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?

Stabilizing selection

How do stabilizing and disruptive selection differ?

Stabilizing selection reduces the amount of variation in a trait. Disruptive selection increases the amount of variation in a trait.

Which statement about genetic drift is correct?

The direction of evolutionary change due to genetic drift is random

Which of the following statements is NOT a part of the Hardy-Weinberg principle?

The genotype frequencies in the offspring generation must add up to two

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?

Disruptive selection

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?

Directional selection

Which statement about inbreeding is correct?

Inbreeding increases the rate of purifying selection.

Why is genetic drift aptly named?

It causes allele frequencies to drift up or down randomly

Why ins't inbreeding considered an evolutionary process?

It does not change allele frequencies

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?

The frequency of the A1 allele is 0.3

Which assumption must be met for a population to be in Hardy-Weinberg equilibrium for a specific gene?

No genetic drift can affect allele frequencies for the gene.

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene?

The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively.

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?

The value of a particular characteristic; characteristics of an organism can include such traits as size and color.

Gene flow can either increase or decrease the average fitness of a population (T/F)

True

The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating. (T/F)

True

Which statement about balancing selection is correct?

When balancing selection occurs, no single phenotype has a distinct advantage over others in terms of fitness.

Genetic drift ___ genetic variation

decreases

Generation-to-generation change in the allele frequencies in a population is ___.

microevolution

Mutation ___ genetic variation

increases

Gene flow ___ the genetic variation between two populations.

may increase or decrease

Selection ___ genetic variation

may increase, decrease or maintain

Which evolutionary mechanism results in adaption?

natural selection