Exam 24: The Origin of Species

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. -Which type of reproductive isolation operates to keep the mosquitofish isolated, even when fish from different ponds are reunited in the same body of water?

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 analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept is most applicable in this example?

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

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: Fossil evidence suggests that polar bears, Ursus maritimus, arose from grizzly bears, Ursus arctos. On average, polar bears are slightly larger than grizzly bears in size and weight. The morphological features/adaptations of polar bears make them well suited to survival in a marine environment. Interbreeding and production of fertile offspring between the two species has been recorded in captivity, and more recently in the wild. -The biological species concept emphasized the absence of gene flow. Which alternative species concept(s)is(are)applicable to explaining the hybridization between grizzly and polar bears?

When male horses (stallions)and female donkeys (jennets)mate, they produce a sterile hybrid called a hinny. Hinnies occur much less frequently than do mules, but are just as healthy and robust as mules. Logically, which of the following best accounts for the relative rarity of hinnies, and what kind of prezygotic isolating mechanism is at work here?

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

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

The largest unit within which gene flow can readily occur is a

Dogs (Canis lupus familiaris)and gray wolves (Canis lupus)can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time)and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species?

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