Chapter 24 Study Questions

True or False: The following example populations meet the basic requirements of Hardy-Weinberg equilibrium.

A small, isolated population of seals living in a stable environment with no genetic mutations.-False A large population of fish where females mate with males based on size.-False A population of birds with no genetic mutations that often mate with members of neighboring bird populations-False A large, isolated population of squirrels that lives in a stable environment, has no genetic mutations, and mates randomly.-True A large population of spiders that experiences immigration from a second nearby population.-False

A gene pool consists of

All alleles for genes in a population.

Why are the terms 'natural selection' and 'evolution' not synonymous?

Because evolution can only change genotype frequencies and natural selection can only change allele frequencies. Because evolution operates on a genetic level and natural selection acts upon phenotypic traits.

A wildfire dramatically reduces a population of oak trees. Several months later, high winds blow several acorns from the surviving oak trees to a meadow several hundred miles away. The acorns germinate and establish a new population of oaks in the meadow. The surviving oaks in the original population will likely experience a ____________ effect, while the oaks in the new population will likely experience a _____________ effect.

Bottleneck; Founder

In a population of 100 four o'clock plants, there are 50 red-flowered plants with genotype CRCR, 30 pink-flowered plants with genotype CRCW, and 20 white-flowered plants with genotype CWCW. Match the correct frequencies for the following alleles and genotypes.

C^RC^R= 0.5 C^RC^W= 0.3 C^WC^W= 0.2 C^R=0.65 C^W=0.35

Identify whether the following evolutionary mechanisms result in changes in allele and genotype frequencies or result in changes in the balance of genotypes.

Changes allele and genotype frequencies: Gene flow & Genetic drift Changes the balance of genotype: Assortative mating & Inbreeding

What advantage do frog eggs that were laid in trees have over frog eggs that were laid in jungle pools?

Decreased predation

Place each phenotype in the category describing the type of selection that will occur.

Directional Selection: Dark Fur& Light fur Diversifying Selection: Dark fur on one island and light fur on another island. & Dark fur in forest and light fur in fields. Stabilizing Selection: Grey fur

Under what conditions do catfish exhibit this walking behavior?

During drought conditions

If the frequency of an allele reaches 1.0, the allele is said to be

Fixed

How might natural selection have resulted in frogs that prefer to lay their eggs on an overhanging leaf rather than in the water?

Frogs that laid their eggs on overhanging leaves had higher reproductive success than frogs that laid their eggs in the water, and this trait spread through the population.

The figure above depicts two deer populations that occasionally interbreed. What evolutionary mechanism is shown and what statement best describes its consequences?

Gene flow - Due to interbreeding between the two populations, the genetic diversity in both will increase over time.

Habitat fragmentation is a big concern to conservation biologists. How will habitat fragmentation affect evolution by genetic drift?

Habitat fragmentation will increase the effect of genetic drift, and lead to a decrease in variation.

Label the allele and genotype frequencies for a population of four o'clock plants in Hardy-Weinberg equilibrium.

If the allele frequency of CR (p) is 0.7, then the allele frequency of CW (q) is 1 - p = 0.3. Likewise, If the allele frequency of CW (q) is 0.3, then the allele frequency of CW (p) is 1 - q = 0.7. If p = 0.7, then the frequency of the CRCR genotype (p2) = (0.7)2 = 0.49. If q = 0.3, then the frequency of the CWCWgenotype (q2) = (0.3)2 = 0.09. If p = 0.7 and q = 0.3, then the frequency of CRCW (2pq) = 2(0.7)(0.3) = 0.42.

How does inbreeding depression decrease a population's fitness?

Inbreeding can increase the frequency of homozygotes for harmful recessive alleles.

All individuals in a population of birds are tagged and measured. The beaks of the birds vary in size from small to large. These data provide evidence for which requirement of natural selection?

Individual variation; Inheritance; Overproduction; Differential reproductive success;

Sexual selection results in nonrandom mating. Indicate which type of sexual selection is being exhibited in these examples.

Intrasexual: Antler, large claws, & large size. Intersexual: nest building, long feathers, & mating calls.

Rank the following mice from greatest reproductive success to least reproductive success over the course of their lifetime.

Mouse B: 1 Mouse A: 5

View the animation below, then complete the quiz to test your knowledge of the concept.

Reduces genetic variation in a population

Fitness is a measure of the _______ of a particular genotype in a population.

Reproductive success

The effect of genetic drift is much more significant in ________ populations.

Small

How might natural selection have resulted in the two-headed snake species commonly having a tail with behavior and color patterns that resemble a head?

Snakes that exhibited these color and behavior patterns were able to avoid predators and reproduce better than those that did not.

Identify whether the following factors that govern microevolution are sources of new genetic variation or mechanisms that alter existing genetic variation.

Source of new genetic variation: Mutations, Gene duplications, Exon shuffling, and Horizontal gene transfer. Mechanism that alters existing genetic variation: Natural selection, genetic drift, migration, and nonrandom mating

A ship was caught in a storm and driven to a small island in the middle of the South Pacific. For generations, no one encountered this small colony, who despite the odds made a thriving settlement on their island. After many years, what characteristics would be unique about this population?

The people on the island would all look very similar to each other, and they may exhibit abnormally high occurrences of traits that are rare in the general human population.

Complete the sentences with the correct terms.

The random change in allele frequencies is called-Genetic Drift Genetic drift can lead to the fixation of an _allele_ and occurs rapidly in _small_ populations. When populations are reduced following a major disaster the resulting random change in allele frequencies is called the _bottleneck effect_ . If the population returns to its pre-disturbance size, genetic variation is generally _lower_ than in the original population. When a few individuals colonize a new location, the subsequent random change in allele frequencies is called the _founder effect_ .

Consider a population of birds with three color morphs, each with a different genotype. Red birds leave 10 offspring in the next generation, orange birds leave 8 offspring, and yellow birds leave 2 offspring. Based on this information, indicate whether the following statements are true or false.

The relative fitness of red birds is 0.5.-False The relative fitness of yellow birds is 0.2.-True The difference in fitness between red and orange birds is 0.1-False The difference in fitness between orange birds and yellow birds is 0.6-True Natural selection would favor red birds over yellow-True

Two species of catfish live in the same river and behave and feed in relatively the same way. One species of catfish exhibits the walking behavior while the other does not. What can be said about the catfish that exhibits the walking behavior as opposed to the one that does not?

The walking catfish will be more likely to reproduce during dry years than the catfish that does not walk.

Which finches survived to reproduce?

Those able to eat the larger seeds

Sexual selection can increase the prevalence of phenotypes that have a relatively lower chance of survival.

True