Which of these are true? a) there are many types of ecosystems all over the world.

b) there are only a few types of ecosystems all over the world.

Which of the four major uses is predicted to change the least by 2020?

1. emigration the movement of people from one place to another 2. immigration a situation in which resources are being used up at a faster rate than they can be replenished 3. migration the leaving of one's homeland to settle in a new place 4. overpopulation the movement of people to a new country 5. sustainable development a situation in which the birth rate is not sufficient to replace the existing population 6. underpopulation the ability to meet current needs without reducing the ability to meet future needs 7. unsustainable development the increase in the population of a city 8. urbanization a situation in which the number of people exceeds the available natural resources in an area

How can you tell the difference between rough er from smooth er?