Chapter 22 Mastering Biology

The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species. How many distinct species, both living and extinct, are depicted in this tree? a. five b. six c. nine d. eleven

11

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.

Conditions 1 and 2

Starting from the wild mustard Brassica oleracea, breeders have created the strains known as Brussels sprouts, broccoli, kale, and cabbage. Therefore, which of the following statements is correct? a. In this wild mustard, there is enough heritable variation to permit these different varieties. b. In wild mustard, most of the variation is due to differences in soil or other aspects of the environment. c. Heritable variation is low in wild mustard-otherwise this wild strain would have different characteristics. d. Natural selection is rare in wild populations of wild mustard.

In this wild mustard, there is enough heritable variation to permit these different varieties

What must be true of any organ described as vestigial? a. It must be homologous to some feature in an ancestor. b. It must be both homologous and analogous to some feature in an ancestor. c. It need be neither homologous nor analogous to some feature in an ancestor. d. It must be analogous to some feature in an ancestor.

It must be homologous to some feature in an ancestor

Which of the following observations led to Darwin's major inferences? a. Members of a population vary in their heritable traits. b. Body parts that are not used deteriorate over time. c. Organisms only go extinct when catastrophes occur. d. Although organisms can produce huge numbers of offspring, many of these offspring do not survive. e. The first and fourth answers are correct.

Members of a population vary in their heritable traits. Although organisms can produce huge numbers of offspring, many of these offspring do not survive.

A group of small fish live in a lake with a uniformly light-brown sandy bottom. Most of the fish are light brown, but about 10% are mottled. This fish species is often prey for large birds that live on the shore. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which of these statements presents the most accurate prediction of what will happen to this fish population? a. There is no way to predict the result. b. In two generations, all the fish will be mottled. c. The ratios will not change. d. The proportion of mottled fish will increase over time. e. As the mottled fish are eaten, more will be produced to fill the gap.

The proportion of mottled fish will increase over time

Members of two different species possess a similar-looking structure that they use in a similar way to perform about the same function. Which of the following would suggest that the relationship more likely represents homology instead of convergent evolution? a. Both species are well adapted to their particular environments. b. The two species live at great distance from each other. c. The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical. d. The structures in adult members of both species are similar in size.

The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, what would happen in environments that lack antibiotics? a. These bacteria would try to make the cost worthwhile by locating and migrating to microenvironments where traces of antibiotics are present. b. These bacteria would be outcompeted and replaced by bacteria that have lost these genes. c. The number of genes conveying antibiotic resistance would increase in these bacteria. d. These genes would be maintained in case the antibiotics appear.

These bacteria would be outcompeted and replaced by bacteria that have lost these genes.

A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations best explains what happened? a. Triazine-resistant weeds were more likely to survive and reproduce. b. Triazine-resistant pigweed has less-efficient photosynthesis metabolism. c. The herbicide company lost its triazine formula and started selling poor-quality triazine. d. Natural selection caused the pigweed to mutate, creating a new triazine-resistant species.

Triazine-resistant weeds were more likely to survive and reproduce

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? a. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. b. The ancestors of these organisms experienced harmful mutations that forced them to lose these structures. c. Natural selection cannot account for losses, but accounts only for new structures and functions. d. Natural selection accounts for these losses by the principle of use and disuse.

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

An adaptation is _____. a. a trait that gives rise to a new species b. the cause of natural selection c. a trait that gives an organism a reproductive advantage in the current environment d. an individual's attempt to conform to its environment e. all of the above

a trait that gives an organism a reproductive advantage in the current environment

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 _____. a. a homologous structure b. convergent evolution c. a vestigial trait d. natural selection

a vestigial trait

Varieties of Staphylococcus aureus that are resistant to the drug methicillin _____. a. developed in response to the use of methicillin b. already existed in the population before methicillin was developed c. always have an advantage in every environment d. were strongly selected for as methicillin became widely used to treat bacterial infections e. The second and fourth answers are correct.

already existed in the population before methicillin was developed AND were strongly selected for as methicillin became widely used to treat bacterial infections

A challenge to traditional (pre-1860) ideas about species came from embryology, when it was discovered that _____. a. embryos of dissimilar organisms, such as sharks and humans, resemble each other b. all animals develop similar embryonic gills c. the more advanced the animal, the more slowly it develops d. mutations have a far more dramatic effect on embryos than on adult organisms e. the embryological development of many plants and animals is almost identical

embryos of dissimilar organisms, such as sharks and humans, resemble each other

After the drought of 1977, researchers hypothesized that on the Galápagos island Daphne Major, medium ground finches with large, deep beaks survived better than those with smaller beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. A tourist company sets up reliable feeding stations with a variety of bird seeds (different types and sizes) so that tourists can get a better look at the finches. Which of these events is now most likely to occur to finch beaks on this island? a. evolution of smaller, pointier beaks over time, until all birds have relatively small, pointy beaks b. increased variation in beak size and shape over time c. evolution of yet larger, deeper beaks over time, until all birds have relatively large, deep beaks d. no change in beak size and shape over time

increased variation in beak size and shape over time

Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms _____. a. use essentially the same genetic code b. show heritable variation c. reproduce d. require energy

use essentially the same genetic code