Which of the following organisms first introduced oxygen into Earth's atmosphere?

A. cyanobacteria

B. methanogens

C. early protozoans

D. plants

E. green algae

Why is it bad to pop your knuckles?

Systems thinking focuses on A. Only the parts of the system not the collective effect B. Exclusively on how ecosystems interact with the environment C. The ways in which systems interact with other systems in the same area D.

In some states, populations of mule deer (Odocoileus hemionus) and white-tail deer (O. virginianus) can occupy the same forest habitat and can be found mixing together in certain areas.

How do economics affects science

Why have only a few people ever seen a total solar eclipse?

Which gas is a source of natural groundwater pollution im thinking its carbon

How many atoms of each element are in the chemical formula p2 O5

Organisms that have groups of specialized cells organized into organs are always

What is a cell how does it effect the body

A farmer crossed a yellow maize plant (Yy) with another yellow maize plant (YY). He planted 200 seeds from this cross. How many of the plants would be yellow?