Why are some ecosystems more productive then others?
a. some ecosystems work harder than others
b. certain ecosystems receive from humans
c. some ecosystems have more nutrients available than others

Which statement is true about the cell theory? a) it is well-supported by evidence. b) it is unchangeable and permanent.

The transport tubes from food came down the plant are called?

Land conservation is a worldwide priority. there are several methods to prevent the loss of land due to a variety of reasons. which method is not a way to conserve land? a) sea walls b) rainwater harvesting c) limits on clear cuts of forests d) cut and burn methods of clearing land