If many cells commit apoptosis in any one organ, what may happen to that particular organ?

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

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because