Reproduction, or reproduction, is a general property live, consisting in ability to reproduce similar to individuals. Reproduction at each look is resulted by continuous generation change and life on Earth does not come to an end.
Instruction
1. Evolutionarily the most ancient form of reproduction on the planet is an asexual reproduction. It represents division of a unicell (or cages of a metaphyte) with formation of the affiliated individuals completely identical to maternal. Such form of a reproduction is most often observed at prokariot, mushrooms, plants, the elementary, meets as well at some animals.
2. Among types of asexual reproduction it is possible to call reproduction division (doubling of a ring chromosome at prokariot, a mitosis at the simplest and monocelled seaweed), a sporoobrazovaniye at mushrooms and plants (the lowest and the highest), vegetative reproduction of the higher plants. Also fragmentation of worms, some seaweed, mold mushrooms, budding of a freshwater hydra and coral polyps belong to asexual reproduction.
3. Asexual reproduction in favorable conditions allows to increase the number of individuals of this look sharply. However all descendants have identical parental the genotype and increases in a genetic variety practically does not occur while the changes acquired during sexual process could be useful to adaptation to the new, changed environmental conditions. For this reason the most part of living organisms constantly or periodically breeds sexually.
4. At sexual reproduction the new individuals appear as a result of merge of two haploid gametes – gametes, and the diploidic zygote from which the germ develops is formed. Gametes are formed in genitals of men's and female individuals. Genetic information of parental individuals unites, increasing a variety and resilience of posterity.
5. In an organism of hermaphrodites – oboyepoly animals – two types of gametes – men's and women's can be formed at the same time. Historically such animals were more ancient. Coelenterates, flat and Annelidas, a number of mollusks treat them. But the diclinous types which appeared later during evolution began to prevail and reached the best development though self-fertilization of hermaphrodites in some cases also has the advantages (for example when the probability to meet the sexual partner is low).
6. Primitive forms of sexual process meet at bacteria and protozoa. So, at paramecium caudata the sexual process is called conjugation during which two infusorians approach and partially exchange with each other hereditary material. At the same time they can have new, useful adaptive properties. But the number of individuals as a result of conjugation at infusorians does not raise therefore it is called sexual process, but not reproduction.
7. One more type of sexual process – copulation. It is observed at a number of unicells: their cages turn into identical gametes and merge, forming a zygote. Only one type of gametes is formed at the most ancient organisms (isogamy), these gametes cannot be distinguished or told whether they are female or men's. At a heterogamy the men's and female gametes (spermatozoa and ova) strongly differ from each other, have the different sizes, the building and functions.