A life cycle includes the various stages in the life of a living thing, including its birth, growth, aging and death. For instance, a butterfly's life cycle chart starts with an egg, moves on to a caterpillar, then a cocoon and goes onto an adult before the chart begins again.
Different living things have different life cycles, so each type of organism requires its own life cycle chart. A tree's life cycle chart, for example, begins with a seed or nut which germinates, forming a seedling. The seedling then grows tall, eventually setting its own seed. The tree then dies, and the cycle starts again with a new seedling sprouting from one of the tree's seeds.
Life cycle charts are not only useful for showing how living things develop, they can illustrate virtually any multi-step process, such as the birth and death of a star. The life cycle for a star similar to the sun begins with the gravitational attraction of gases in a nebula, eventually becoming so compressed that nuclear fusion begins. The chart then goes on to show how the star fuses heavier elements until it forms iron, after which it can no longer perform fusion. The last part of the chart shows the growth of the star into a red giant and its decline into a white dwarf.