Reproduction in Organisms Test - 17

Megaspore mother cell undergoes meiotic division to reduce the number of chromosome to half. Meiotic or reduction division occurs in two steps to produce four haploid megaspores.

Sexually reproducing organisms produce two different kinds of gametes. Generally, male gametes are motile and smaller in size but female gametes are non-motile containing abundant food.

In aquatic organisms fusion of nuclei occurs outside the body of the female. The male and female release their gametes into water and they are brought together by water current. Such Syngamy is called external fertilisation.

Zygote divide mitotically to produce a number of cells. These cells arrange into different layers and specialised into different tissues to form organ by the process of differentiation.

All sexually reproducing organisms develops from single cell called zygote. Zygote is formed by fusion of male and female gametes. Traits from male and female are present in the zygote.

Sexual reproduction is comparatively slower mode of reproduction than asexual reproduction. The formation of gametes, there fusion and embryo formation takes longer duration.

During formation of ovum (oogenesis), meiosis division occurs but unequal division leads to formation of one functional egg after meiosis II division along with three polar bodies.

Self-pollination involve transfer of pollen grain from anther to stigma of same flower. As both gametes have similar genetic makeup, the plant becomes homozygous for its characters due to continued self-pollination.

Pollen grains are produced inside the anther of stamen. Each pollen grain produces two male gametes that lead to double fertilisation. The Anther is generally bilobed structure located at the tips of stamen.

In flowering plants, double fertilisation occurs. Each anther produces two haploid male gametes. One gamete fuse with egg called syngamy and other fuse with polar nuclei called triple fission.