Question

explain how the male germ gametes reaches the female germ cell for fertilisation ​

Answer 1

Sexual reproduction refers to the sexual germ cells (gametes) produced by the parents, through the combination of bisexual germ cells (such as sperm and egg cells), become the fertilized egg, and then the fertilized egg develops into a new individual, called sexuality reproduction. Extensive variation in gene combinations in sexual reproduction can increase the ability of offspring to adapt to natural selection. Randomly combined genes in offspring of sexual reproduction may or may not be beneficial to the species, but at least increase the chances of a few individuals surviving in an unpredictable and ever-changing environment, thereby benefiting the species. Sexual reproduction can also promote the spread of favorable mutations in the population. If two individuals in a species have favorable mutations at different sites, in the asexual reproduction population, the two mutants will compete until one elimination, it is impossible to retain both favorable mutations at the same time. However, in sexual reproduction populations, through mating and recombination, these two favorable mutations can simultaneously enter the genome of the same individual and simultaneously spread in the population. For the above reasons, sexual reproduction accelerates the process of evolution. In the more than 3 billion years of biological evolution on Earth, the first two billion years of life have remained in the asexual reproduction stage, and the evolution has been slow, and the evolution rate has accelerated significantly since the last 1 billion years. In addition to changes in the earth's environment (such as the emergence of the oxygen-containing atmosphere, etc.), the occurrence and development of sexual reproduction is also a major cause.

Answer 2

$\large{\underline{\underline{\mathfrak{ Fertilization \colon}}}}$

The process of fusion of the male gamete and female gamete is termed as Fertilization.

$\underline{\underline{\sf Fertilization \ in \ Humans \colon}}$

• The ejaculation of the spermatozoa (male gamete) into vagina is termed as Insemination.

• Further,the sperms descend into the uterus wherein they get capacitated. Capacitation is the process of entry of calcium ions and removal of cholesterol ions leading to the whiplash moment of sperms.

• Meanwhile,the ovum descends from the ovaries into the ampulla.

The events during the fusion of sperm and ova can be categorised as :

Acrosomal Reactions

• Sperm releases certain lysins which degenerate the layers of ovum.

• Corona radiata is degenerated due to the action of Corona Penetrating Enzyme.

• Acrosin digests Zona Pellucida

Cortical and Zona Reactions

• When the sperm reaches the ova,sodium ions make the ovum wall incompatible to fuse with other sperms.

• Release of Cortical Granules constitutes the Cortical Reactions

• While zona reaction is the inability of z.pellucida to fuse with more sperms.

The ovum and sperm finally fuse giving rise to a diploid zygote which further undergoes successive mitotic divisions to form Morula, Gastrula and so on leading to a multi cellular fetus.