Unit 7 Learning Catalytics

Which of these conditions are always true of populations evolving due to natural selection?

Condition 1: The population must vary in traits that are heritable.

Condition 2: Some heritable traits must increase reproductive success.

Condition 3: Individuals pass on most traits that they acquire during their lifetime.

1. Condition 2 only

2. Condition 1 only

3. Conditions 1 and 2

4. Conditions 2 and 3

3. Conditions 1 and 2

After the drought of 1977, researchers on the island of Daphne Major hypothesized that medium ground finches that had large, deep beaks, survived better than those with smaller beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. If this hypothesis is correct, what would you expect to observe if a population of these medium ground finches colonizes a nearby island where Tribulus cistoides is the most abundant food for the next 1000 years? Assume that (1) even the survivors of the 1977 drought sometimes had difficulty cracking the tough T. cistoides fruits and would eat other seeds when offered a choice; and (2) food availability is the primary limit on finch fitness on this new island.

1. no change in beak size and shape

2. evolution of yet larger, deeper beaks over time

3. random fluctuations in beak size and shape

4. evolution of smaller, pointier beaks over time

2. evolution of yet larger, deeper beaks over time

Many crustaceans (for example, lobsters, shrimp, and crayfish) use their tails to swim, but crabs have reduced tails that curl under their shells and are not used in swimming. This is an example of _____.

1. vestigial trait

2. homologous structure

3. convergent evolution

4. natural selection

1. vestigial trait

Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?

1. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

2. Natural selection cannot account for losses, but accounts only for new structures and functions.

3. Natural selection accounts for these losses by the principle of use and disuse.

4. The ancestors of these organisms experienced harmful mutations that forced them to lose these structures.

1. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals that are heterozygous for this allele?

1. 0.16

2. 0.04

3. 0.32

4. 0.020

3. 0.32

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer or more than this have reduced fitness. Which of the following terms best describes this situation?

1. disruptive selection

2. stabilizing selection

3. sexual selection

4. directional selection

2. stabilizing selection

You want to study divergence of populations, and you need to maximize the rate of divergence to see results within the period of your grant funding. You will form a new population by taking some individuals from a source population and isolating them so the two populations cannot interbreed. What combination of characteristics would maximize your chance of seeing divergence in this study?

1. Choose a random sample of individuals to form the new population.

2. Choose individuals from one extreme to form the new population.

3. Choose a species to study that produces many offspring.

4. Choose a species to study that produces a few, large offspring.

5. Place the new population in the same type of environment as the source population.

6. Place the new population in a novel environment compared to that of the source population.

2, 3, and 5

2, 3, and 6

1, 4, and 6

1, 3, and 6

2, 3, and 6

Use the following description to answer the question(s) below.

In the ocean, on either side of the Isthmus of Panama, are thirty species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are fifteen species on the Pacific side and fifteen different species on the Atlantic side. The Isthmus of Panama started rising about ten million years ago. The oceans were completely separated by the isthmus about three million years ago.

In the following figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

1. Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting in faster divergence in deepwater shrimp.

2. They have been geographically isolated from each other for a longer time.

3. The rise of the land bridge was accompanied by much volcanic activity. Volcanic ash contains heavy metals, which are known mutagens. Ash fall caused high levels of heavy metals in the ocean sediments underlying the deep water, resulting in accelerated mutation rates and faster divergence in deepwater shrimp.

4. Fresh water entering the ocean from the canal is both less dense and cloudier than seawater. The cloudy fresh water interferes with the ability of shallow-water shrimp to locate mating partners, which reduces the frequency of mating, thereby slowing the introduction of genetic variation.

2. They have been geographically isolated from each other for a longer time.

All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than five hundred million years ago.

Fruit-fly eyes are of the compound type, which is structurally very different from the camera-type eyes of mammals. Even the camera-type eyes of molluscs, such as octopi, are structurally quite different from those of mammals. Yet, fruit flies, octopi, and mammals possess very similar versions of Pax-6. The fact that the same gene helps produce very different types of eyes is most likely due to _____.

1. the few differences in nucleotide sequence among the Pax-6 genes of these organisms

2. differences in the control of Pax-6 expression among these organisms

3. variations in the number of Pax-6 genes among these organisms

4. the independent evolution of this gene at many different times during animal evolution

2. differences in the control of Pax-6 expression among these organisms

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of _____.

1. the influence of environment on development

2. change in a developmental gene or its regulation that altered the spatial organization of body parts

3. heterochrony

4. paedomorphosis

2. change in a developmental gene or its regulation that altered the spatial organization of body parts

Rank the following in order from most general to most specific:
1. gametic isolation
2. reproductive isolating mechanism
3. sperm-egg incompatibility in sea urchins
4. prezygotic isolating mechanism

 

1. 2, 3, 1, 4

2. 2, 4, 1, 3

3. 4, 1, 2, 3

4. 4, 2, 1, 3

2. 2, 4, 1, 3