Introduction to sexual reproduction in humans
Reproduction is the process by which humans gives rise to new individuals. Sexual reproduction is the process that involves the fusion of two gametes, sperm (male gamete) and egg (female gamete). In human these gametes are produced in different sexes, the male and female. Reproduction in humans is performed by reproductive systems, the male and female reproductive systems. The main organs of male reproductive system are testis and gonads and of female reproductive system are vagina, ovaries, and uterus. Main events in sexual reproduction of humans are production of sperms and egg, copulation, and fertilization. (Sexual Reproduction in Humans) : Production of Gametes
Sperms are produced in seminiferous tubules present in male reproductive organ testis. This process is known as spermatogenesis. The precursors of the sperm the diploid spermatogonium divides mitotically to produce numerous spermatogonia and differentiate into spermatocytes. Spermatocytes undergo meiotic cell division to produce, 4 haploid spermatids. Spermatids differentiate and develop into sperm. Sperms are single celled male gametes with a head, midpiece, and a tail. Ovum (egg cell), the female gamete is produced in the ovaries of female reproductive system. This process is known as oogenesis. In contrast to males, in females the initial steps in egg production occur prior to their birth. Diploid oogonia and primary oocytes produced in fetus and by the time she is born, females have about 1–2 million oocytes. In oocytes the first meiotic division (meiosis I) will initiated and then stopped. No further development occurs until the girl becomes sexually mature. After maturity the primary oocytes recommence their development, usually one at a time and once a month. The primary oocyte grows further and completes the meiosis I, forming a large secondary oocyte and a small polar body. Only after fertilization meiosis II will be completed. By completion of meiosis II secondary oocyte gets converted into a fertilized egg or zygote. (sexual Reproduction in Humans) :copulation
Sperms produced in males are deposited into vagina through the process called copulation. Copulation in humans occurs through penis. Penis ejaculates semen (a mixture of sperm and accessory fluids) into the vagina. The sperm along with accessory fluids passes through the urethra and reach vagina. Fertilization
After copulation sperm cells swim with help of tail and reached egg cell. When sperm binds to the egg cell fertilization begins and produces zygote (fertilized egg). Zygote divides further to produce embryo which finally gives rise to new individual.
Introduction to modes of reproduction used by single organisms : Reproduction is the process by which new individual organisms (offspring) are produced from their parents. The continuity of life on earth is as the result of reproduction. There are mainly two modes of reproduction, namely: Sexual and Asexual reproduction. Asexual reproduction involves only one parent and produces offspring that are identical to the parent, where as Sexual reproduction typically requires the involvement of two individuals or gametes, one each from opposite type of sex. Asexual Reproduction:
Asexual reproduction is the mode of reproduction used by single organisms. It is the process by which an organism produces a genetically-similar or identical copy of itself without a contribution of genetic material from another individual. Types of asexual reproduction:
Budding, Fragmentation, Binary fission, Parthogenesis, sporogenesis, Vegetative propagation etc are the different modes of reproduction used by single organisms. Budding:
Yeast is a single-celled organism. The small bulb-like projection coming out from the yeast cell is called a bud. The bud gradually grows and gets detached from the parent cell and forms a new yeast cell. The new yeast cell grows, matures and produces more yeast cells. If...
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