Environmental biology examines the impact of human activities on ecosystems, one of the many Biology Topics.
What are the procedures involved in sexual reproduction in animals?
Sexual reproduction is the most common method of reproduction in animals. In sexual reproduction in animals, there are two parents : a male and a female. The two parents have sex organs which produce sex cells or gametes. The male parent has sex organs called ‘testes’ which produce male sex cells (or male gametes) called sperms. The female parent has female sex organs called ‘ovaries’ which produce female sex cells (or female gametes) called eggs (or ova).
The whole process of sexual reproduction in animals involves the formation of sperms and eggs, joining together of sperm and egg to form a fertilised egg called ‘zygote’, and growth and development of zygote to form a baby animal. The sexual reproduction in animals takes place in the following steps :
- The male parent produces male gametes called sperms.
- The female parent produces female gametes called eggs (or ova).
- The sperm enters into the egg. The nucleus of sperm fuses with the nucleus of egg cell to form a new cell called zygote (The zygote is a fertilised egg).
- The zygote divides repeatedly to form a hollow ball of hundreds of cells which is called embryo.
- Embryo grows and becomes a foetus (in which all the main body features of the baby animal have formed).
- Foetus grows and develops to form a new baby animal.
Sexual Reproduction In Humans
In human beings, there are special reproductive organs to make sperms and eggs ; to bring together sperms and eggs for fertilisation and make a zygote ; and for the growth and development of a zygote into a baby. We will first describe the reproductive systems of human male (man) and human female (woman), and then discuss how reproduction takes place in human beings.
The Male Reproductive System
The human male reproductive system consists of the following organs: Testes, Scrotal sacs, Epididymis, Sperm ducts, Seminal vesicles and Penis. The human male reproductive system is shown in Figure. Since the human male is called man, so we can also say that it is the reproductive system of man.
Testes are the oval shaped organs which lie outside the abdominal cavity of a man (see Figure). A man has two testes (singular of testes is testis). Testes are the real reproductive organs in man. The male sex cells (or male gametes) called ‘sperms’ are made in testes. Thus, testes make male gametes called sperms. Millions of sperms are produced in the testes. The testes are enclosed in two small bags of skin called scrotal sacs (see Figure). The testes work more efficiently at a temperature slightly below the body temperature, so they are held outside the body in the scrotal sacs.
The sperms formed in testes come out and go into a coiled tube called epididymis (see Figure). The sperms get stored temporarily in epididymis. From epididymis, the sperms are carried by a long tube called sperm duct into organs called seminal vesicles (see Figure). The sperms get stored in seminal vesicles. The seminal vesicles join to another tube called urethra coming from the bladder (see Figure). Urethra carries the sperms to an organ called penis which opens outside the body (These sperms are carried in a liquid called semen). The penis is an organ for introducing sperms into the woman. The penis passes the sperms from the mans body to the woman’s body for the purpose of reproduction. The male reproductive system is designed to manufacture sperms and to deliver them to the place where one of them will be able to fuse with an egg cell (female gamete) and bring about fertilisation.
The Female Reproductive System
The human female reproductive system consists of the following organs: Ovaries, Oviducts, Uterus, and Vagina. The human female reproductive system is shown in Figure. Since the human female is called woman, so we can also say that it is the reproductive system of woman.
Ovaries are the oval shaped organs which are inside the abdominal cavity of a woman (see Figure). A woman has two ovaries. Ovaries are the real reproductive organs in a woman. The female sex cells (or female gametes) called ‘eggs’ or ‘ova’ are made in the ovaries. Thus, ovaries make the female gametes called eggs (or ova). Just above the ovaries are the tubes called ‘oviducts’ (which are also known as
fallopian tubes). The oviducts are not directly connected to ovaries but have funnel shaped openings which almost cover the ovaries (see Figure). The egg (or ovum) released by an ovary goes into the oviduct through its funnel-shaped opening. In human beings, one mature egg is released into oviduct every month by one of the ovaries. The release of an egg (or ovum) from the ovary is called ovulation. The fertilisation of egg by a sperm takes place in the oviduct.
The two oviducts connect to a bag like organ called uterus (or womb) at their other end (see Figure). The growth and development of a fertilised egg (or zygote) into a baby takes place in the uterus (or womb). Thus, uterus is the part where development of the baby takes place. The uterus is connected through a narrow opening called cervix to another tube called vagina which opens to the outside of the body (see Figure). Vagina receives the penis for putting sperms into the woman’s body.
We will now describe the process of sexual reproduction in humans. The process of reproduction in humans takes place in two steps :
- Fertilisation, and
- Development of embryo.
We will discuss both these processes, one by one.