Biology Ch. 16

Remember that color is an inherited trait in beetles. Which of the following is an example of natural selection?

Green beetles leave more offspring than brown beetles because they are better at finding food.

The evolution of populations due to chance is

genetic drift

In a population with brown and green alleles for color, genetic drift

has more effect on the evolution of a small population

What process helps gene flow happen in animal populations?

migration

A patient has an infection of Streptococcus bacteria. She takes azithromycin, which kills off 99% of a bacterial population. All surviving bacteria are resistant to azithromycin. What has occurred in this bacterial population?

natural selection

Approximately 65 million years ago, a mass extinction occurred on planet Earth. Layers of soil dating back to this time contain large amounts of the radioactive element iridium. This indicates that a large asteroid or comet struck Earth, throwing up huge clouds of debris, which would block much of the sunlight. Food became very scarce. Half of the marine species and nearly all of the dinosaur species went extinct during this time. Soon after the cloud settled, the surviving species of mammals rapidly diversified and filled the niches left empty by the dinosaurs. What evolutionary event was driven by this asteroid collision and the resulting cloud?

natural selection

A biologist studying evolution starts with a single cell of E. coli and grows a population of one billion bacteria from it. Which rule of Hardy-Weinberg must be broken first before evolution will occur in this population?

no new mutations

Which term from the Hardy-Weinberg equilibrium represents the frequency of the homozygous dominant genotype?

p^2

On which of the following is natural selection based?

phenotype

Which of the following is the smallest group that can evolve?

population

Males of a species are usually more brightly colored and/or have ornaments or special abilities. This is an example of what type of selection?

sexual selection

What is meant by directional selection?

Directional selection favors an extreme version of a trait.

In a species of snail, dark-shelled individuals are better hidden from bird predators in the shady forest, while light-shelled individuals are better hidden in well-lit brushy edge areas. If there were no areas of intermediate brightness in this habitat, which type of selection would act on shell color in these snails?

Disruptive selection

Which of the following alleles is most likely to decrease in frequency in a population?

an allele causing infertility

Which of the following is represented by a wolf that hunts rabbits?

biotic predator

A forest fire kills off 90% of a rabbit population. What has occurred in this population?

bottleneck

Which of the following is a result of nonrandom mating within a population?

inbreeding

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

microevolution

Color is an inherited trait in beetles. If brown beetles move into a population from a nearby island, which of the following statements is correct?

Gene flow causes the frequency of the brown allele to increase.

What causes two different populations of the same species to have many of the same alleles, even if the alleles first arose after the populations had split?

Gene flow occurs between populations.

A dam is built on a river upstream of a population of trout. The trout experience a dramatic reduction in their habitat. What evolutionary event has likely occurred to this population?

reduction in diversity due to a bottleneck

Which of the following is true about natural selection?

Natural selection acts on individuals.

You see a dog with completely black fur. What can you say about fur color genetics in this dog?

Nothing. Only that the phenotype of the dog is black.

When the common phrase "survival of the fittest" is used to describe evolution in a population, what determines how fit an individual is?

reproductive success

Small lizards have difficulty defending their territory, but large lizards are more likely to be preyed upon by owls. Which type of selection would act on body size in these lizards under these conditions?

Stabilizing selection

Why are elephant tusks unlikely to get much longer, even though the tusks have obvious advantages?

Stabilizing selection will keep the trait at its current average length.

If color is an inherited trait in beetles, and birds are more likely to eat brown beetles than green beetles,

the frequency of the green allele will increase.

How often will a new, heritable mutation of a human gene appear?

The mutation will appear in one out of 80 million children.

In a certain population of mice, the frequency of the brown fur allele is 0.4, and the frequency of the black fur allele is 0.6. In the next generation, the frequency of the brown fur allele drops to 0.3. What has happened in this population?

The population has evolved.

Which of the following is a correctly stated condition that must be true for a population to be in Hardy-Weinberg equilibrium?

The population must be large.

What condition is necessary for genetic drift to have a significant effect on a population?

The population needs to be small.

In a population of 100 hamsters, there are 30 total alleles for black fur. What is the frequency of the black fur allele?

0.15

If q in a population is 0.3, what is p?

0.7

Which of the following are causes of evolutionary change?

1) genetic drift 2) mutation 3) gene flow 4) natural selection

Can you match these biology terms with their definitions?

1. A(n) mutation is a change in the base sequence of an organism's DNA. 2. A population is said to be in equilibrium if its allele frequencies remain constant from one generation to the next. 3. A(n) adaptation is a trait that increases an individual's ability to survive and reproduce in a specific environment, and may modify a population over generations. 4. An organism's traits--including its outward appearance, behavior, and other observable or measurable features--is known as its phenotype. 5. Selection can influence populations in three ways: directional selection favors one extreme in a range of phenotypes; disruptive selection favors both extremes in a range of phenotypes; and stabilizing selection favors the average phenotype in a population. 6. A(n) population consists of all the members of a species that live together in a specific geographic region. 7. An organism's genetic makeup--its actual combination of alleles--is known as its genotype.

True or False. In the example described in the tutorial, the red amoebas survived the catastrophic event, and all future generations of amoebas were red because the red amoebas had a higher reproductive rate than the blue ones.

False

Which of the following would be a situation similar to genetic drift?

Flip a coin twice, and write down the results. Do this four times. The coin comes up heads each time.

How do founder effect, genetic drift, and a bottleneck relate to each other?

Founder effect and bottleneck are types of genetic drift.

In humans, the allele for Huntington's disease is dominant. What does this mean?

Huntington's disease will occur in someone with both a healthy allele and a Huntington allele.

Why is natural selection based entirely on reproductive success?

If more offspring expressing a particular phenotype are born, the frequency of the allele responsible for that phenotype increases.

Which of the following events could NOT be caused by a population bottleneck?

Increased population size

Which of the following statements about the amoeba population described at the end of the tutorial is true?

It is more vulnerable to extinction due to lack of genetic variation.

There are several types of bacteria that are resistant to most, if not all, currently available antibiotics. Which of the following best explains the mechanism of this resistance?

One or a few bacteria have a mutation that makes them resistant to the antibiotic. The resistant bacteria survive and reproduce in the presence of the antibiotic.

The Hardy-Weinberg principle relies on which concept?

Populations evolve only when specific conditions occur.

Why do most mutations occur?

Random errors in DNA replication cause mutation.