Chapter 24; Origin of Species

Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?

A) a behavioural reproductive isolating mechanism

According to the concept of punctuated equilibrium, ________.

A) a new species accumulates most of its unique features as it comes into existence

Speciation ________.

A) can involve changes to a single gene

Other than predation by introduced Nile perch, the most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is ________.

A) fusion

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species. These two juniper species are kept separate by ________.

A) gametic isolation

Most causes of speciation are relatively slow, in that they may take many generations to see changes, with the exception of ________.

A) polyploidy

A small number of birds arrive on an island from a neighbouring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighbouring island arrive. These new arrivals ________.

A) tend to retard adaptation to the new food plants

Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be ________.

B) 28

The difference between geographic isolation and habitat differentiation (isolation) is the ________.

D) relative locations of two populations as speciation occurs

The western rosella (Platycercus icterotis) is a medium-sized parrot whose range is confined to the south-west portion of Western Australia. Imagine that a few individuals were taken to Brisbane, Queensland and were released. Subsequently, these individuals established a breeding population and gradually expanded their range westwards. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. If the two forms were unable to interbreed when their expanding ranges met, it would be an example of ________.

B) allopatric speciation

How are two different species most likely to evolve from one ancestral species?

B) allopatrically, after the ancestral species has split into two populations

Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?

B) biological

What does the biological species concept use as the primary criterion for determining species boundaries?

B) gene flow

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

B) genetic isolation, genetic drift, divergence

You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use?

B) morphological

Two hypothetical species of Australian tree frogs which live sympatrically in northeastern Victoria differ in ploidy: Species A is diploid, and Species B is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which difference most likely evolved first?

B) polyploidy

Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. These two frog species separate by ________.

B) reduced hybrid viability

In a hypothetical situation, a certain species of flea feeds only on water buffalo. In the Northern Territory, water buffalo and domestic cattle often associate with one another in the same habitat. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of ________.

B) sympatric speciation and habitat isolation

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South Australia. If reinforcement is occurring, what would you expect if you compare the calls of the two species in zones of sympatry versus zones of allopatry?

C) Calls would be more different in areas of sympatry.

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 they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

C) Postzygotic isolation exists between the two frog species.

A hybrid zone is properly defined as ________.

C) an area where mating occurs between members of two closely related species, producing viable offspring

According to the biological species concept, for speciation to occur, ________.

C) at least one gene, affecting at least one phenotypic trait, must change

Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?

C) habitat isolation

Reinforcement is most likely to occur when ________.

C) hybrids have lower fitness than either parent population

The production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) is an example of ________.

C) reduced hybrid fertility

Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in autumn. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

D) Their winter habitat has no bearing on their degree of reproductive isolation.

The largest unit within which gene flow can readily occur is ________.

D) a species

The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and ________.

D) an increasing number of viable, fertile hybrids is produced over the course of the next one hundred generations