Photosynthesis occurs when
a. plants absorb energy from carbon dioxide
b. plants absorb energy from sunlight
c. oxygen concentration in the atmosphere increases
d. all of the above

How many trophic levels are there in the following food chain? phytoplankton - shrimp - perch - pike - osprey

How are the testes and ovaries similar? a. both produce sex cells. b. both connect internal reproductive organs to the exterior. c. both transport sex cells from their site of production. d. both store mature sex cells.

This is an active transport mechanism by which cells pump sodium and potassium ions against the concentration gradient