Living in the Environment 18th Edition by Tyler Miller,Scott Spoolman

Exercise 22

What is the key concept for this section What is biological extinction Explain what a trophic cascade is and give an example. What is a mass extinction What is the background extinction rate , and how do estimated current and projected extinction rates compare with it What percentage of the earth's land and what percentage of the earth's oceans have been disturbed by human activities Explain how scientists estimate extinction rates and describe three problems they face. Give three reasons why many extinction experts believe that projected extinction rates are probably on the low side. What percentage of the world's species are likely to go extinct, largely as a result of human activities, during this century Distinguish between endangered species and threatened species and give an example of each. List four characteristics that make some species especially vulnerable to extinction.