Crossing over is a method of (blank)?

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

Acceleration is a direct result of a.) balanced forces b.) unbalanced forces c.) gravity d.) velocity hurry!

Which of these is true for bacteria because they are prokaryotic cells? a. they can engulf body cells in order to make memory cells. b. they must invade viruses in order to reproduce. c. they are much larger than eukaryotic body cells. d. they can reproduce on their own outside of other cells.