Fertilisation

Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, insemination, pollination,[1] fecundation, syngamy and impregnation,[2] is the fusion of gametes to initiate the development of a new individual organism.[3] The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.

In Antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic.[4]

In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frogs.[5] In 1827, von Baer observed a mammalian egg for the first time.[4] Oscar Hertwig (1876), in Germany, described the fusion of nuclei of spermatozoa and of ova from sea urchin.[5]

The evolution of fertilisation is related to the origin of meiosis, as both are part of sexual reproduction, originated in eukaryotes. There are two conflicting theories on how the couple meiosis–fertilisation arose. One is that it evolved from prokaryotic sex (bacterial recombination) as eukaryotes evolved from prokaryotes.[6] The other is that mitosis originated meiosis.[7]

The gametes that participate in fertilisation of plants are the pollen (male), and the egg (female) cell. Various families of plants have differing methods by which the female gametophyte is fertilized. In Bryophyte land plants, fertilisation takes place within the archegonium. In flowering plants a second fertilisation event involves another sperm cell and the central cell which is a second female gamete. In flowering plants there are two sperm from each pollen grain.

In seed plants, after pollination, a pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle. The sperm are transferred from the pollen through the pollen tube to the ovule.

Pollen tube growth

This page was last edited on 11 July 2018, at 08:15 (UTC).
Reference: https://en.wikipedia.org/wiki/Fertilized under CC BY-SA license.

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