What is Reproduction?
Posted on October 8, 2007
Filed Under Pregnancy | Leave a Comment
The complex, seemingly magical process of fashioning a baby is by now quite well understood. And this process is a far cry from the primordial beginnings of life on this planet. The earliest life was probably a single celled organism that reproduced by division into two similar organisms. And when those two organisms had grown to adult size, each of them divided into two. There were no special sex cells and no separate sexes. Some simple animals such as amoebas and paramecia still adhere to this primitive reproduction pattern.The process of the union of the sex cells, as it occurs in humans and other mammals, did not just happen it evolved through many steps, some of which we can trace. More primitive forms of life such as simple marine animals like the starfish have a very wasteful form of sexual reproduction. There are two sexes, but the sperm and eggs are discharged haphazardly without any physical awareness or even proximity between the two parents. A more advanced stage in the evolution of the union of the sex cells is illustrated by fish. There is a strong physical awareness between male and female during mating, but absence of physical contact. The male swims above the female and as she discharges her eggs he discharges his sperm. In the frog, which has a still more advanced pattern of mating behavior, there is not only sex awareness, but actual physical contact.
The male clasps the back of the female with a specialized clasp organ and as she discharges her eggs, he discharges his sperm upon them. All varieties of external insemination, however, are relatively wasteful and inefficient.
Internal insemination, as practiced by humans, by the other mammals, and by many sub mammalian forms, is far more efficient. In this pattern of reproduction, a special organ of the male, the penis is inserted into a special organ of the female, the vagina. In addition to depositing the semen well on the way to the precise area where it is to function, this method of introducing the male ejaculatory organ deep within the body of the female protects the spermatozoa by releasing them in a highly favorable environment. Such conditions as temperature and moisture within the cervical canal, the uterus, and the fallopian tubes of the female reproductive tract are optimal for the conservation of sperm.
Tags:amoebas, eggs, mammals, marine animals, mating behavior, organisms, Pregnancy, sex cells, sexes, sexual reproduction sperm
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