What are some of the sources of generic variations

Food webs - transferring energy and matter from one level to another. here you see four food webs. one or more are incorrect. which food web(s) show the correct sequence of organisms, from start to top level consumer? a) a b) d c) c d) a and d

Which coal field location is related to coal fields in the eastern united states and supports the theory of continental drift? eastern india southern africa western australia northern south america

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.