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Thinking Scientifically
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1. A researcher sets up an experiment in which two genetically different populations of fruit fly are placed in two enclosed areas that are connected by a narrow tube, through which the flies can fit. Suggest two scenarios that can occur in the entire set-up, over time.

2. Each island of the Greater Antilles is home to a similar-appearing assortment of anoles (fig 16.12). However, mtDNA analysis showed that the anoles from different islands that resemble each other are not alike genetically. How is this possible?

3. Give three examples from the chapter of events that may not have occurred as we initially thought they did based on the most obvious evidence.

4. Some species today have a background extinction rate of 20 to 200 per million species per year. How extensive an elevation is that compared to the typical estimate of background extinction rate?

5. Investigation of fossilized eggshells from a huge bird (Genyormis newtoni) show that it became extinct about 50,000 years ago in Australia, a time that coincided with human colonization, What types of evidence would support or refute the hypothesis that humans hunted the bird into extinction?


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Additional Questions and Terms

1. At the Charles Darwin Research Station on Santa Cruz Island in the Galapagos hundreds of tortoises are rescued from poachers. Conservation biologists are comparing mtDNA sequences among the tortoises to classify them into their 11 subspecies so that each animal can be returned to its native island.

  • a. How is this use of mtDNA analysis different from others discussed in the chapter?
  • b. What might happen if tortoises are placed at random on the islands?
  • c. How can researchers tell if tortoises from different subspecies might have mated with each other while in captivity?
  • 2. The fossil record indicates that about 65 million years ago, many types of sea urchins vanished from the seas surrounding North America. The species that disappeared had no specialized feeding structures, and got nourishment by eating organic debris on the ocean bottom. Survivors had specialized structures called tube feet to obtain nourishment from a variety of surfaces, and also ate a variety of things. Populations with these adaptations survived, but the animals were much smaller than they had been before the asteroid impact of the time. What is the mechanism of extinction of the doomed sea urchin species?

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