Life cycles.

Meaning: This means that living organisms go through a series of stages from birth to death, and then the cycle begins again with new life.

Choice of Words: Life refers to the state of being alive or the existence of living organisms. Cycles means a series of events that happen repeatedly in the same order. Here, 'Life cycles' implies that living organisms go through a series of stages from birth to death, and then the cycle begins again with new life.