Ch 17 - Practice Test

Explain why naming and describing species based only on their appearance can be problematic.

In some cases, individuals that look the same are actually different species. For example, the cordilleran flycatcher and the Pacific slope flycatcher look so similar that birdwatchers have difficulty telling them apart, but they are two different species that do not interbreed. In other cases, individuals that look very different are the same species. For example, the myrtle warbler and Audubon's warbler were once classified as separate species because they have different-colored throat feathers, but they are the same species.

What events can push a species to extinction?

Possible causes of extinction include loss of a food source, hybridization, loss of habitat, and competition with another species for resources.

Modern biologists have identified two main factors that drive speciation. What are these factors?

The factors are isolation and genetic divergence.

Organisms from two separate species can look anatomically similar.

True

In the late 1700s, two populations of minnows became isolated when an earthquake altered the path of a river. Now the populations can no longer successfully breed with each other even when they are both moved to the same pond. These organisms have undergone ________ speciation.

allopatric

The most common cause of extinction is

habitat change

Hybrid inviability is an example of a(n) ________ isolating mechanism.

postmating

Before the modern era of science, organisms were assigned to species on the basis of

similarities in appearance

A European species of marsh grass called Spartina maritima has a diploid number (2n) of 60. A similar species native to North America, S. alterniflora, has 2n = 62. In 1835, the North American species was found growing near the European species in Southampton, England, after being accidentally imported. Occasional sterile hybrids were noted. In 1895 a new species, S. anglica, was first identified at Southampton and subsequently became common. The new species has been identified as a fertile hybrid of the original two species. What is the 2n chromosome number of the hybrids that formed from the original two species S. maritima and S. alterniflora?

61

Researchers believe that at least ________ % of the species that have lived on Earth have become extinct.

99.9

A single species of finch from South America was displaced to a new habitat in the Galápagos Islands and evolved rapidly into several new species as it exploited the new resources. What occurred in these Darwin's finches?

Adaptive radiation

When a species invades a new habitat and evolves rapidly into several new species to better exploit new resources, what has occurred?

Adaptive radiation

From an evolutionary perspective, explain how three species of large, flightless birds (ostriches, rheas, and emus) came to occupy the widely separated landmasses of Africa, South America, and Australia.

All of these birds evolved from a common "ratite" ancestor that lived on the supercontinent called Gondwana. In response to the extreme geographic isolation resulting from continental drift, allopatric speciation occurred and resulted in the three unique ratite species that are now found on the three different continents.

What happens when two populations become geographically separated from each other and then genetic divergence occurs?

Allopatric speciation

What is the best explanation for the origin of the unique species recently found in the Annamite Mountains of Vietnam?

Allopatric speciation

Hybridization of two species in which of the following cases could lead to the extinction of one of the original species?

An endangered species may further decline by producing less-fit hybrid offspring.

In what type of habitat, or under what types of environmental conditions, would you expect adaptive radiation to occur?

Any habitat in which many different types of unexploited food resources and few or no competitors exist is ideal for adaptive radiation. This seems to be the case in Darwin's finches of the Galápagos Islands, the cichlids of Lake Malawi, and other classic examples of adaptive radiation.

Oceanic islands are not the only geographic habitats that can harbor isolated populations of individuals. What are some other examples of isolated "island" populations?

Any habitat that contains a boundary that the organism cannot cross is considered an "island"-for example, a mountaintop, a small pond in the middle of an arid region, or even a living host (for a parasite).

Which statement best describes the reproductive isolation between populations of Rhagoletis flies, one of which is found on apple trees and the other that is found on hawthorn trees?

Apple-liking males are more likely to encounter apple-liking females than hawthorn-liking females.

Which species is least likely to become extinct? A) A fish species found in all five of the Great Lakes B) A mammal species that can live equally well on dry land and in fresh water C) A mammal species that feeds on a rare tropical orchid D) A fish species that feeds on only rare snails found in only one small river E) A fish species that has hybridized with another species to produce infertile offspring

B) A mammal species that can live equally well on dry land and in fresh water

A plant breeder can use plum pollen to hand-fertilize an apricot flower. The fruit contains fertile seed that grows into a hybrid called a plucot. However, in the natural environment, plums and apricots bloom several weeks apart. Why are plums and apricots considered separate species?

Because the flowering occurs at two different times, the plants are temporally isolated. This premating isolation mechanism keeps them reproductively isolated in nature, a characteristic of separate species.

Female blue-footed boobies of the Galápagos Islands will mate only after a specific courtship display on the part of the male. The male high-steps to advertise his bright blue feet. What mechanism describes why the females do not mate with other species of boobies?

Behavioral isolation

Which of the following is the most prevalent immediate cause of extinction? A) Competition B) Specialization C) Environmental change D) Predation E) Disease

C) Environmental change

Which species is most likely to become extinct? A) The white tiger beetle, found throughout several mid-Atlantic U.S. states B) The northeastern pygmy shrew, found throughout New Jersey and Pennsylvania C) Kirtland's warbler, which breeds in only a small area of Michigan D) The jack-in-the-pulpit, found throughout the eastern United States and Canada E) Carp, found throughout Europe, the United States, and Canada

C) Kirtland's warbler, which breeds in only a small area of Michigan

Which of these definitions of species best matches the biological species concept? A) Members of the same species look almost exactly alike. B) Members of the same species are all morphologically similar. C) Members of the same species are all genetically identical. D) Members of the same species can mate and produce fertile offspring. E) Members of the same species are whatever an expert says they are.

D) Members of the same species can mate and produce fertile offspring.

Einkorn (Triticum boeoticum) is an ancient grain with a diploid number of 14 (2n = 14). Durum (Triticum turgidum) appeared later. Durum grains are larger and the plant is hardier. It has twice the genetic material of Einkorn (2n = 28) but contains basically the same chromosomes. Can you propose a hypothesis on how durum evolved?

Durum could possibly be a polyploidy of einkorn. Polyploid plants are common and may become new species.

Which statement best describes how overspecialization can affect a species? A)Highly specialized adaptations enable a species to live anywhere on Earth. B) Highly specialized adaptations are rare in species that occupy a very limited geographic range. C) New adaptations will never occur in a highly specialized species. D) If the habitat around a specialized species changes, the species always evolves new specialized adaptations. E) Highly specialized adaptations in a species increase the likelihood of extinction if the environment changes.

E) Highly specialized adaptations in a species increase the likelihood of extinction if the environment changes.

Where would a researcher most likely find examples of allopatric speciation? A) On the surface of a large lake B) In a desert lacking sand dunes or rock formations C) At the bottom of a sandy, slowly flowing river D) In a large, flat prairie lacking any significant water E) On a mountain range with many steep valleys and turbulent rivers

E) On a mountain range with many steep valleys and turbulent rivers

Two species of garter snakes live in the same geographic area. One lives mainly in water and the other mainly on land; therefore, they rarely encounter each other and do not interbreed. What type of isolation is this?

Ecological

Hybrid inviability occurs when two species mate and produce fertile offspring.

False

Polyploidy is an important mechanism of speciation in animals.

False

Two species of plants that both use honeybees as pollinators but reproduce at different times of the year-one spring, the other midsummer-demonstrate geographic isolation.

False

Horses and donkeys can mate successfully to produce mules, which are always sterile. Which genetic isolating mechanism prevents horses and donkeys from becoming a single species?

Hybrid infertility

Fruit fly species all look similar to one another. If you have a male and a female fruit fly, how can you prove that they are the same species, according to the biological species concept?

If they mate successfully and their offspring are fertile, they are the same species.

A horse has a diploid number (2n) of 64 and a donkey has 2n = 62. The hybrid of these two species, mules, have 2n = 63 and are sterile. Why are mules sterile?

One chromosome is unpaired and fails to divide properly during meiosis

All members of the golden hamster species known today are descendants of a single litter collected in Syria in 1939. Its diploid chromosome number is 44. Two other species of hamster, each with a diploid number of 22, overlap geographically in Syria. The golden hamster is thought to be a new species from the mating of a male and female of the two other hamster species. What mechanism might explain this recent event of speciation?

Polyploidy

How do premating isolation mechanisms differ from postmating isolation mechanisms?

Premating isolation mechanisms prevent mating from ever occurring, whereas postmating isolation mechanisms occur after mating and prevent the hybrid offspring from passing on its genes.

The parasitic Rhagoletis flies show such a preference for either hawthorn or apple trees that they are no longer interbreeding populations. What type of speciation does this scenario illustrate?

Sympatric

Two species of pines, Pinus radiata and Pinus muricota, live in the same regions of California and are capable of forming hybrids under laboratory conditions. However, they do not interbreed because one releases pollen in February and the other in April. What genetic isolating mechanism is involved?

Temporal

What are the five premating isolating mechanisms that keep different species from successfully mating?

The mechanisms are geographic isolation, ecological isolation, temporal isolation, behavioral isolation, and mechanical incompatibility.

Polyploidy is an important mechanism of speciation in plants.

True

Premating isolation mechanisms occur when two species have different and incompatible mating behaviors.

True

Gametic incompatibility is an example of

a postmating isolating mechanism

Temporal isolation is an example of

a premating isolating mechanism

The introduction of a new species into an area that has several different habitats and very rich resources, but no predators will likely lead to

adaptive radiation

The origins of 300 or more species of cichlid fish in Lake Malawi can best be explained by

adaptive radiation

The series of events depicted in the figure demonstrates

allopatric speciation

There are currently many similar-looking but different species on either side of the Isthmus of Panama. They most likely resulted from

allopatric speciation

Two species of squirrels live on either side of the Grand Canyon. It is believed that a long time ago, before being separated by the canyon, they were the same species. This is an example of

allopatric speciation.

Overspecialized adaptations

are the result of natural selection.

In many species of fireflies, males flash light from their abdomens to attract females. Each species has a different flashing pattern. This is an example of

behavioral isolation

Interbreeding two different species of lovebirds produces offspring that are unable to build a nest after they mature because they lack the appropriate nest-building behavior needed to build a nest. This limits genetic mixing between the species due to

behavioral isolation

Strong courtship displays like the one in the figure below can lead to

behavioral isolation

The elaborate courtship rituals of many bird species help to preserve their genetic isolation through

behavioral isolation

Eastern and Western meadowlarks look almost identical and sometimes inhabit the same areas of prairies. These birds recognize members of their own species by distinctive songs and thus do not breed with each other. This is an example of

behavioral isolation.

Two populations of plants look identical but their flowers are fertilized by different pollinators-one by a night-flying hummingbird moth, the other by honeybees. These two populations of flowers are examples of

different species

One species of fish feeds in the muddy bottom of a lake. A second species eats insects that land on the water surface. This is an example of

ecological isolation

The immediate cause of most extinctions is

environmental change.

The biological species concept cannot be applied to

extinct organisms

In northern Minnesota, the lynx (Lynx canadensis) habitat overlaps the bobcat (Lynx rufus) habitat. The two can breed and produce healthy, fertile offspring, which could lead to

extinction of one or both species.

The introduction of a few individuals into a new habitat that is unoccupied by other members of the species is a(n)

founder event

When the pollen of one plant species will not germinate on the flower of another species, it is an example of

gametic incompatibility

One method of maintaining the genetic isolation of a population is the inability of sperm to fertilize eggs of a different species. This is called

gametic incompatibility.

For new species to develop, there must be ________ in the population.

genetic divergence

Two organisms that live on different islands are experiencing ________ isolation.

geographic

The Kaibab squirrel lives on the north side of the Grand Canyon, and the Abert squirrel lives on the south side. Even though these two populations are only miles apart, their gene pools are kept isolated by

geographic isolation

Crossing a zebra with a horse produces sterile offspring. This is an example of

hybrid infertility

If a hybrid is unable to produce sperm because meiosis does not proceed correctly, gene flow between the species is restricted by

hybrid infertility

Lions and tigers can interbreed and produce offspring called tiglons or ligers, which have normal life spans but are sterile. Lions and tigers remain isolated genetically because of

hybrid infertility

When hybrid offspring are created between species but are unable to breed successfully, it is referred to as ________.

hybrid infertility

When offspring are infertile after breeding occurs between individuals of different species, the genetic identities of the two populations are protected by

hybrid infertility

A pet store puts both Norway rats (Rattus norvegicus) and black rats (Rattus rattus) in the same cage. If mating occurs, the pregnancy will not succeed because the embryos fail to develop properly. This is an example of

hybrid inviability

Store-bought hybrid tomatoes are very popular with consumers. Suppose you buy a tomato from the grocery store, collect seeds from it, and plant the seeds. If the seeds do not germinate, the seedlings fail to thrive, or the plants die quickly after sprouting, what reproductive isolating mechanism might be responsible?

hybrid inviability

When some hybrid organisms do not live long, it is an example of

hybrid inviability

Populations that were once considered separate species are sometimes reassigned to the same species because

it was discovered that they can produce viable and fertile offspring.

The Great Dane and the Chihuahua are both domestic dogs (the same species), but mating between them is limited because of

mechanical incompatibility

Two species of snails are physically unable to mate. This is an example of

mechanical incompatibility

The biological concept of species requires that

organisms reproduce sexually

The organisms most likely to undergo sympatric speciation by polyploidy are

plants

A flower has four copies of each chromosome. This is an example of ________.

polyploidy

Mechanisms that prevent mating between species are called ________ isolating mechanisms.

premating

The biological species concept is based on the idea that individuals in one group are be unable to breed with individuals outside their group. This phenomenon is referred to as ________.

reproductive isolation

Since the Pleistocene ice age, deserts have been gradually forming in the southwestern United States. As the original lakes and rivers of this area shrank into isolated streams, ponds, and springs, the fishes living in them developed a strong potential for

speciation

A group of an interbreeding natural population that is reproductively isolated from other such groups is called a

species

One species of moss in upstate New York produces gametes in May, and another species of moss in the same region produces gametes in June. This is an example of a(n) ________ isolating mechanism.

temporal

Two different species of pine release their pollen at different times of the year. This is an example of

temporal isolation

Two populations of plants found in the same meadow look identical but are fertilized by different pollinators-one by a night-flying hummingbird moth, the other by honeybees that fly by day. This is an example of

temporal isolation

When two organisms reach sexual maturity at different times, it is an example of

temporal isolation

Two fossils may be assigned to different species if

they are anatomically different.