What causes allopatric speciation in nature?

When analyzing tree rings, what do scientists assume a thin ring indicates?

Acommon kind of mechanical weathering is called

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.