Definition - What does Fertilization mean?

Fertilization involves the fusion of sex cells or gametes to initiate the development of a newly fertilized egg.

In animals, the mature male sperm combines with the female egg to form a new organism known as a zygote. Conversely, fertilization in plants is led by pollination, through which a mature pollen grain (male gamete) is transported (usually by wind, insects, or birds) and comes into contact with the microspore (female gamete).

MaximumYield explains Fertilization

Fertilization involves three main steps that confirm species-specificity. The three phases are:

  • Chemotaxis - The movement of an organism in response to a chemical stimulus
  • Acrosomal reaction - The reaction that takes place in the acrosome of the sperm as it gets into the egg
  • Sperm adhesion - The adaptation tactics developed by the gametes

In animals, fertilization can either be external or internal depending on the method of conception. The animals whose fertilization is internal are called viviparous, while the ones with external fertilization are known as oviparous animals.

Fertilization in both plants and animals trigger a series of reactions in the egg.

In animals the egg membrane changes to prevent both attachment and penetration of more than a single sperm in the ovum. However, some species may experience polyspermy (having more than one spermatozoon attaching and penetrating the egg); whereby in such a situation the egg nucleus only fuses with a single spermatozoal nucleus.

Plants also require the sperm and the egg cell for fertilization to occur. Flowering plants undergoes two propagation processes whereby the second process involves the fusion of another female sex cell (the inner cell), and another mature male gamete. Each pollen grain in flowering plants contains two sperms. On the contrary, seed plants undergo a different process. After pollination, there is the germination of a pollen grain followed by the growth of a pollen tube that penetrates into the ovule through a microscopic pore known as a micropyle. The male gametes are transported from the pollen past the pollen tube.

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