Chapter 9, Problem 2CR

To determine

The key concept for Section 9.1. Define biological extinction? Explain a trophic cascade and give an example. Define mass extinction and the background extinction rate. The way in which estimated current and projected extinction rates compare with it. The percentage of the Earth’s land and percentage of the Earth’s oceans that have been disturbed by human activities. Explain the way in which 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. The 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.