Biology 2 Exam 1

Which of the following describes the most likely order of events in allopatric speciation?

genetic isolation, genetic drift, and divergence

Which statement about genetic drift is correct?

The direction of evolutionary change due to genetic drift is random.

A computer simulation shows how genetic drift affects the frequency of allele A over 100 generations. One of the eight replicates is colored blue and another is colored red to ease comparison. Describe how the graph for a population size of 400 would be different for a population size of 4000.

The fluctuations of allele frequencies would be less dramatic over 100 generations for a population of 4000 than it is for a population of 400.

In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy-Weinberg equilibrium?

The frequency of allele a is 0.1. Babies with cystic fibrosis are genotype aa (q2 in the Hardy-Weinberg equation). So, 0.1 × 0.1 × 2500 = 25.

Which species concept would be most useful to a team of biology students conducting a biodiversity survey on their campus?

The morphospecies concept

A post-zygotic barrier will happen:

After fertilization

"Two populations of organisms are separated by a geographical barrier." This is:

Allopatric speciation

What is an allele?

Alternative forms of the same gene

"If these populations are capable of interbreeding, they are the same species." This is:

Biological Species concept

A prezygotic barrier will happen

Before fertilization

Predict how prickles ("thorns") originated in roses.

By chance, a mutation occurred in some roses that resulted in sharp bumps on the stems. Individuals with these early prickles survived herbivore attacks and produced more offspring than roses without the mutation, increasing the frequency of the prickled roses in the population over time.

Why does natural selection not produce populations that are perfectly adapted to their environment?

Changing environments may change the nature of adaptive traits in a population.

This type of selection favors one extreme, changes the mean, and reduces variation.

Directional selection

This type of selection favors both extremes and increases genetic variation.

Disruptive selection

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

Disruptive selection

"The movement of alleles into or out of a population," This is:

Gene flow

Select the correct statement about gene flow.

Gene flow makes allele frequencies more similar between populations.

The founder effect and genetic bottleneck are examples of:

Genetic drift

Predict how the allele frequencies of a sea turtle population are likely to change if 50 percent of the population starts with normal pigmentation (AA and Aa) and 50 percent are albino (aa). Assume albino turtles are more visible to predators.

If the population were under Hardy-Weinberg equilibrium then the allele frequencies would be q = 0.7 (the square root of q2 = 0.5) and p = 0.3 (because p + q = 1), and these allele frequencies would not change over time. However, directional selection is likely to occur because albino sea turtles are more visible and thus more vulnerable to predators than sea turtles with normal pigmentation. The frequency of the A allele is likely to increase and the frequency of the a allele is likely to decrease over time.

The fossil record resembles the living species in the same geographic area. How does this pattern support the theory of evolution by natural selection?

It is evidence that species can change over time.

Select the example of intersexual selection.

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

How did the 1977 drought on Daphne Major cause evolutionary change in the medium ground finch population?

Medium ground finches with large and deep beaks had higher survival rates during the drought.

"If these populations look similar or the same, they are the same species." This is:

Morphological species concept

The random change in allele frequency that produces new alleles

Mutation

Which evolutionary mechanism increases genetic variation in a population?

Mutation

The change in allele frequencies due to differential reproduction and survival

Natural Selection

Which evolutionary mechanism results in adaptation?

Natural selection

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.

A population at Time 1 consists of 20 AA, 5 Aa, and 2 aa individuals. After a genetic bottleneck, at Time 2, there is 1 AA, 1 Aa, and 1 aa. Compare the frequencies of the a allele at Time 1 and Time 2.

Original population at Time 1: freq(a) = q = (5 + 2 + 2)/54 = 0.17; new population at Time 2: freq(a) = q = (1 + 1 + 1)/6 = 0.50. The frequency of a has increased dramatically due to genetic drift from the bottleneck.

"If these populations are descended from a common ancestor, they are the same species." This is:

Phylogenetic species concept

Which is the first step in allopatric speciation?

Physical isolation of two populations

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when the hybrids mate with other hybrids or with adults of either species, they are rarely successful in producing offspring. What can you infer from this information?

Postzygotic isolation exists between the two frog species.

Why do related species share homologous traits?

Related species inherited homologous traits from a common ancestor.

Evaluate this statement: Mutations are bad.

Some mutations are deleterious, but others can be beneficial or neutral.

This type of selection favors the mean, reduces the extremes, and reduces variation. This is:

Stabilizing selection

"two populations live in the same area but are separated by a reproductive barrier". This is:

Sympatric speciation

Evaluate this statement: Gene flow increases the genetic divergence of populations.

This statement is false. Gene flow reduces the divergence of populations.

Which is an example of a structural homology?

Vertebrate forelimbs generally have the same number and a similar arrangement of bones.

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

When antibiotics are overused, susceptible bacteria are constantly being killed off, even when an infection is not present. However, any individual bacteria that are resistant to these antibiotics will survive and multiply, reducing the likelihood that antibiotic treatment will be effective in the future.

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?

behavioral isolation

A researcher notices that in a certain moth species, some females prefer to feed and lay eggs on domesticated solanaceous plants like potatoes and tomatoes. Other females prefer to feed and lay eggs on wild solanaceous plants such as Datura. Both male and female moths primarily use scent to find these plants from afar. Females tend to mate where they feed, and the researcher finds a genetic basis for scent preference in these moths. Based on the above information, what might be occurring in this moth species?

divergence in sympatry

The change in allele frequencies over time

evolution

Use the following description to answer the question(s) below.On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island's lowlands, and is also found on the African mainland, located about 200 miles away. The very closely related species Drosophila santomea is found at higher elevations and only on Sao Tomé. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, where hybrids are greatly outnumbered by D. santomea. Studies of the two species' nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago.Which of the following reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?

hybrid sterility

Which of the following groups could be identified using the biological species concept?

sunflower & lizard species living today