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Chapter 21

30 November, 2015 - 14:23
  1. Figure 21.6 The ground is permanently frozen so the seeds will keep, even if the electricity fails.
  2. C
  3. B
  4. C
  5. B
  6. C
  7. C
  8. C
  9. D
  10. Crop plants are derived from wild plants, and genes from wild relatives are frequently brought into crop varieties by plant breeders to add valued characteristics to the crops. If the wild species are lost, then this genetic variation would no longer be available.
  11. Secondary plant compounds are toxins produced by plants to kill predators trying to eat them; some of these compounds can be used as drugs. Animal toxins, such as snake venom, can be used as medicine. (Alternate answer: antibiotics are compounds produced by bacteria and fungi which can be used to kill bacteria.)
  12. Human population growth leads to unsustainable resource use, which causes habitat destruction to build new human settlements, create agricultural fields, and so on. Larger human populations have also led to unsustainable fishing and hunting of wild animal populations. Excessive use of fossil fuels also leads to global warming.
  13. The frog is at risk from global warming shifting its preferred habitat up the mountain. In addition, it will be at risk from exotic species, either as a new predator or through the impact of transmitted diseases such as chytridiomycosis. It is also possible that habitat destruction will threaten the species.
  15. Many species will disappear from the ecosystem when a keystone species is removed.