Exam 24: The Origin of Species

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

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 hybridise, 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 paragraph, which of the following is the best initial hypothesis for how D. santomea descended from D. yakuba?

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 ________.

House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. 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 ________.

How do hybrid zones slow reproductive isolation?

In the oceans 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. The oceans were completely separated by the isthmus about 3 million years ago. In the 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. -The Panama Canal was completed in 1914, and its depth is about 15 metres. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal? The Panama Canal was completed in 1914, and its depth is about 15 metres. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal?

In the oceans 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. The oceans were completely separated by the isthmus about 3 million years ago. In the 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? Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

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

A hybrid zone is properly defined as ________.

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

Two species of tree frogs that live sympatrically differ in ploidy: Hyla chrysoscelis is diploid, and Hyla versicolour 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?

The question refers to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right), and the vertical axis represents morphological change. Which conclusion can be drawn from this evolutionary tree?

According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that ________.

There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans or into a separate species of their own. Most DNA sequence data analysed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept describing species relationship between modern humans and Neanderthals is most applicable in these observations?

Beetle pollinators of a particular plant are attracted to its flowers' bright orange colour. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it?

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns and cattle often associate with one another in the same open rangeland. 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 ________.

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 ________.

Plant species A has a diploid chromosome 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

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