Chapter 3 of 3

Life Together: Evolution and Ecosystems

A population is a group of organisms of the same species in an area; a species is commonly introduced as organisms that can reproduce together and produce fertile offspring, though this definition has limits. Explore evolution, changes in inherited characteristics of populations over generations, and natural selection, the process through which inherited differences affect survival and reproduction. Then study ecosystems, living communities together with their nonliving surroundings, tracing energy through food webs—networks of feeding relationships—and matter through cycles, like materials repeatedly reused in a community.