reproduction

reproduction Process by which living organisms create new organisms similar to themselves. Reproduction may be sexual or asexual, the first being the fusion of two special reproductive cells from different parents, and the second being the generation of new organisms from a single organism. Asexual reproduction is the more limited, found mainly in protozoan, some invertebrates, and in many plants. By contrast, almost all living organisms have the capacity for sexual reproduction. In the majority of cases, the species has two kinds of individuals – male and female – with different sex functions. Male and female sex cells (in animals, sperm and egg) fuse to produce a new cell, the zygote, which contains genetic information from both parents, and from which a new individual develops. Advances in human reproduction include artificial in vitro fertilization (IVF) in which a woman's ovaries are fertilized in the laboratory and then inserted into her uterus. A controversial reproduction method for animals has produced clones from a single original parent. Some organisms are hermaphrodites, each individual of the species having male and female functions, so that when two of them mate each individual fertilizes the other's eggs. Sexually reproducing plants (or generations) are called gametophyte; ones which reproduce asexually, sporophyte. See also alternation of generations; pollen