Exam 24: The Origin of Species

The next few questions refer to the following description. 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 320 kilometres away.At higher elevations,and only on Sao Tomé,is found the very closely related Drosophila santomea.The two species can hybridize,though male hybrids are sterile.A hybrid zone exists at middle elevations,though hybrids there 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?

Suppose that a group of male pied flycatchers migrated from a region where there were no collared flycatchers to a region where both species were present.Assuming events like this are very rare,which of the following scenarios is least likely?

The next few questions refer to the following description. On the Bahamian island of Andros,mosquitofish populations live in various,now-isolated,freshwater ponds that were once united.Currently,some predator-rich ponds have mosquitofish that can swim in short,fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time.When placed together in the same body of water,the two kinds of female mosquitofish exhibit exclusive breeding preferences. -The predatory fish rely on visual cues and speed to capture mosquitofish.Mosquitofish rely on speed and visual cues to avoid the predatory fish.Which adaptation(s)might help the predators survive in ponds that are home to faster mosquitofish? 1)directional selection for increased speed 2)stabilizing selection for speed that matches that of the mosquitofish 3)change in hunting behaviour that replaces reliance on visual cues with reliance on tactile cues,which can be used to hunt at night 4)change in hunting behaviour that eliminates speed in favour of better camouflage,which permits an ambush strategy

If the low number of hybrid flies in the hybrid zone,relative to the number of D.santomea flies there,is due to the fact that hybrids are poorly adapted to conditions in the hybrid zone,and if fewer hybrid flies are produced with the passage of time,these conditions will most likely lead to

Use the following information to answer the question(s)below. A female fly,full of fertilized eggs,is swept by high winds to an island far out to sea.She is the first fly to arrive on this island and the only fly to arrive in this way.Thousands of years later,her numerous offspring occupy the island,but none of them resembles her.There are,instead,several species,each of which eats only a certain type of food.None of the species can fly and their balancing organs (halteres)are now used in courtship displays.The male members of each species bear modified halteres that are unique in appearance to their species.Females bear vestigial halteres.The ranges of all of the daughter species overlap -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?

A hybrid zone is properly defined as

Which of the following statements about speciation is correct?

Rocky Mountain juniper (Juniperus scopulorum)and one-seeded juniper (J.monosperma)have overlapping ranges.If 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,then which of these terms are applicable? 1)sympatric species 2)prezygotic isolation 3)postzygotic isolation 4)allopatric species 5)habitat isolation 6)reduced hybrid fertility

Use the following information to answer the question(s)below. Two populations of birds with somewhat different colouration live on opposite sides of an island.The habitat between the populations is not suitable for these birds.When birds from the two populations are brought together,they produce young whose appearance is intermediate between the two parents.These offspring will breed with each other or with birds from either parent population,and all offspring of these pairings appear intermediate to various degrees. -What keeps the two populations separate?

The next few questions refer to the following description. In the ocean,on either side of the Isthmus of Panama,are 30 species of snapping shrimp; some are shallow-water species,others are adapted to deep water.There are 15 species on the Pacific side and 15 different species on the Atlantic side.The Isthmus of Panama started rising about 10 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 sea water on either side of the isthmus is separated into five depth habitats (1-5),with 1 being the shallowest. -In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4?

Among known plant species,which of these have been the two most commonly occurring phenomena that have led to the origin of new species? 1)allopatric speciation 2)sympatric speciation 3)sexual selection 4)polyploidy

Prezygotic barriers include all of the following,except for

In a hypothetical situation,the National Park Service,which administers Grand Canyon National Park in Arizona,builds a footbridge over the Colorado River at the bottom of the canyon.The footbridge permits interspersal of two closely related antelope squirrels.Previously,one type of squirrel had been restricted to the terrain south of the river,and the other type had been restricted to terrain on the north side of the river.Immediately before and ten years after the bridge's completion,researchers collected ten antelope squirrels from both sides of the river,took blood samples,and collected frequencies of alleles unique to the two types of antelope squirrels (see the following graphs). -The data in the previous graphs indicate that

Which of these should decline in hybrid zones where reinforcement is occurring?

Allopatric speciation is most likely to be observed among which species?

Two closely related populations of mice have been separated for many generations by a river.Climatic change causes the river to dry up,thereby bringing the mice populations back into contact in a zone of overlap.Which of the following is not a possible outcome when they meet?

The next few questions refer to the following description. 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 320 kilometres away.At higher elevations,and only on Sao Tomé,is found the very closely related Drosophila santomea.The two species can hybridize,though male hybrids are sterile.A hybrid zone exists at middle elevations,though hybrids there 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. -Using only the information provided in the description,which of the following is the best initial hypothesis for how D.santomea descended from D.yakuba?

The next few questions refer to the following evolutionary tree,whose horizontal axis represents time (present time is on the far right)and whose vertical axis represents morphological change. -Which conclusion can be drawn from this evolutionary tree?

A narrow hybrid zone separates the toad species Bombina bombina and Bombina variegata.What is true of those alleles that are unique to the parental species?

The difference between geographic isolation and habitat differentiation is the