ZT-Biology: Polar bear evolution

生物学
Polar bear evolution


1. What is the main purpose of the lecture?

  • A To compare the behaviors of three different bear species 
  • B To examine changes to the habitat in which polar bears live 
  • C To discuss recent insights into polar bear evolution 
  • D To illustrate a new method of DNA analysis used in climate studies

2. Why did  the professor mentions use mitochondrial DNA for testing instead of nuclear DNA?
[CHOOSE 2 ANSWERS]

  • A Mitochondrial DNA has a more stable structure than nuclear DNA has.
  • B Mitochondrial DNA has a shape that is more easily identifiable than that of nuclear DNA.
  • C Mitochondrial DNA is present in larger quantities in cells than nuclear DNA.
  • D Mitochondrial DNA analysis is a better-understood research tool than nuclear DNA analysis

3. What point does the professor make about brown bears?

  • A They now compare with polar bears for food- and territory.
  • B They are the ancestors of polar bears.
  • C They face the same environmental threat as polar bears.
  • D Their jawbones can be easily distinguished from those of polar bears.

4. According to the professor, what do researchers believe about the Svalbard islands?

  • A Polar bears first came into existence as a species on the islands.
  • B The separate islands were once joined together in a single large landmass.
  • C  Interbreeding between polar bears and a species of brown bear occurred on the islands. 
  • D The islands provided a refuge for polar bears during an ancient warming period.

5. What does the professor imply when she discusses the current warming period?

  • A The consequences of the current warming period will not be as serious as most scientists believe. 
  • B The current warming period is progressing more slowly than previous warming periods.
  • C Arctic temperatures today are similar to temperatures during previous warming periods.
  • D The fast pace of the current warming period will threaten polar bears’ long-term survival.

6. Why does the professor imply when she says this: 【音频缺失】

  • A The size of the grizzly bear population will soon stabilize.
  • B The future of the polar bear as a distinct species might be at risk.
  • C Hybridization has already diminished the polar bear population within a short period of time.
  • D Hybrid species do not adapt well to sudden changes in the environment.

答案:C AC B D D B

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