What is it called when changes occur in an ecosystem that already exists? *

a. primary succession
b. secondary succession
c. pollution

Which of the following occurs most often in a population when genetic variation and overproduction are present? some organisms have a lower reproductive success than others. some organisms have a higher reproductive success than others. some organisms have no reproductive success. some organisms do not have genetic variation.

Which prefix mean under less or below

Identify two examples of chemical reactions that you have encountered during the last week. identify an exothermic and endothermic reaction. explain.