Exam 14: The Origin of Species

The emergence of a new plant species over a brief period of time followed by a long period of little change is consistent with which of the following theories?

Speciation without geographic isolation is called ________ speciation.

In a hybrid zone, ________ can occur if the reproductive barrier between two species is weak, as seen among cichlids in the murky waters of modern Lake Victoria.

The biological species concept is

When plants undergo allopatric speciation, an initial reproductive barrier is often

Which of the following types of reproductive barriers separates two species of sea cucumbers whose sperm and eggs often bump into each other but do not cross-fertilize because of incompatible proteins on their surfaces?

Two bird species overlap in a hybrid zone. They are isolated by a slight difference in the male songs and by the females' tendency to select males with the "correct" song. Hybrid offspring tend to have reduced fertility compared to either of the parent species. What effect might natural selection have in this situation?

Two species that sometimes mate and produce vigorous but sterile offspring are affected by

In the North Pacific Ocean, two groups of the same species of killer whales (Orcinus orca) appear to be forming two different species based on what they eat. One group eats fish and the other eats mammals such as seals. Scientists can tell what they eat based on their teeth, because whales that feed on fish have significantly different wear patterns. -Which of the following would be the least useful procedure to perform in determining whether or not this speciation has occurred?

Frequently, a group of related species will each have a unique courtship ritual that must be performed correctly for both partners to be willing to mate. Such a ritual constitutes a ________ and ________ reproductive barrier.

In 2004, scientists announced the discovery of the fossil remains of some extremely short early humans on the Indonesian island of Flores. The new species has been named Homo floresiensis. One hypothesis is that H. floresiensis evolved from Homo erectus, another early human species. How did a population of H. erectus become isolated on this remote island? Early humans constructed boats and rafts, so perhaps they were blown far off course by strong winds during a storm. H. erectus averaged almost 6 feet in height, but the remains show that adults of H. floresiensis were only about 3 feet tall. It is hypothesized that limited resources on this hot and humid island (only 31 square miles) exerted selection pressure, and succeeding generations began to shrink in size. Small bodies require less food, use less energy, and are easier to cool than larger bodies. Evolution of small size in similar circumstances has been observed in many other species but never before in humans. This find demonstrates that evolutionary forces operate on humans in the same way as on all other organisms. -The evolution of H. floresiensis is an example of

Speciation, or the formation of new species, is

Which of these is the best hypothesis about what led to the change seen in the data?

The fossil record shows that for many plant and animal groups, the time between speciation events

Most polyploid species arise from

In a population of plants with a diploid number of 12, a new individual appeared with a chromosome number of 24. If this organism could self-fertilize, forming offspring with the same number of chromosomes (24), scientists would consider this an example of

Two populations of organisms belong to the same biological species when they

Speciation often occurs when a habitat becomes more heterogeneous. In Lake Victoria different species of cichlids are found in different areas of the lake. The best explanation for this speciation is that

In the North Pacific Ocean, two groups of the same species of killer whales (Orcinus orca) appear to be forming two different species based on what they eat. One group eats fish and the other eats mammals such as seals. Scientists can tell what they eat based on their teeth, because whales that feed on fish have significantly different wear patterns. -Another difference between the two groups is in how they hunt. Whales that hunt fish tend to travel in large pods (groups of whales) and vocalize often. Whales that hunt seals, however, tend to travel in very small groups and vocalize very little, likely because of the excellent hearing ability of seals. If these differences brought about speciation, the separation would be considered