Life cycle means how a living thing is born, grows up, gets older, reproduces and dies.
In some cases the process is slow, and the changes are gradual. Humans have stages[disambiguation needed] in the life cycle, such as zygote, embryo, child and adult. The transition from child to adult is slow and continuous. In many societies it is marked by ceremonies at puberty.
In most insects the transition is sharp and well-defined: egg > larva > pupa > imago (adult). In many parasites different stages may take place in different hosts: egg > snail > mammal is a common life history for many parasites of herbivorous mammals.