Exam 14: The Origin of Species

After reading the paragraphs below, answer the questions that follow. 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. -If H. floresiensis were reunited with H. erectus at a much later date, but the two populations could no longer interbreed, it would be correct to conclude that

Which of the following types of reproductive barriers separates a pair of species that could interbreed but for the fact that one mates at dusk and the other at dawn?

Under the biological species concept, a species is a group of organisms that

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

The biological species concept is

In bowerbirds, the divergence illustrated in the figure is based on

After reading the paragraphs below, answer the questions that follow. 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

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 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?

Diane Dodd raised different fruit fly populations on different food sources. She found that after about 40 generations the evolution of reproductive isolation was under way. The mechanism of evolution responsible for this was

Sympatric speciation commonly occurs through ________ in plants but is more likely to occur through ________ in animals.

Diane Dodd's experiments using fruit flies demonstrated that

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

The Monterey pine and the Bishop's pine inhabit some of the same areas of central California. The Monterey pine releases pollen in February, while the Bishop's pine does so in April. This is an example of ________ isolation.

After reading the paragraph below, answer the questions that follow. 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. -One of the finest available sequences of fossils shows how horses have changed slowly and by subtle steps from small shrub-browsing ancestors to the large, grass-grazing modern horse. A large number of fossil species have been named, and it is often difficult to decide on the identity of a fossil horse because transitional forms are common. The species concept most applicable to these organisms would be

Which of the following types of reproductive barriers separates a pair of moth species that could interbreed but for the fact that the females' mating pheromones are not attractive to the males of the other species?

Speciation, or the formation of new species, is

Which of the following statements about plant speciation and hybridization is false?