Pronunciation: LIF SI-k’l

Etymology: The phrase is derived from two common English words. Life is derived from the Old English word for life or body. Cycle is derived from the Greek for circle (kyklos, σπέρμα).

Life Cycle (also called Life History) is the developmental history of an organism. Often, it refers to the sexual life cycle (gametes to zygote to development of other stages that produce gametes). Many organisms go through sexual life cycles in which generations alternate between haploid and diploid phases. However, many organisms do not experience sexual reproduction, and those that do sometimes have asexual (text with tooltip) As the name implies, asexual reproduction is the formation of offspring without the union of gametes. Usually, asexual reproduction involves the production of specialized cells or multicellular structures that can give rise to new individuals. or vegetative stages.

The life cycle illustrated below is that of a blood fluke. Except for the egg and sperm, the animal is diploid throughout its life and goes through different developmental larval stages in the water (the miracidium) and in the snail (as a metacercaria), which releases an infective cercaria stage that burrows through the skin of the host.

Life cycle of Schistosoma from Barnes, R. D. 1980. Invertebrate Zoology. Saunders College, Philadelphia.

By Jack R. Holt. Last revised: 01/02/2009