Class 8 Biology Chapter 09 Reproduction in animals CBSE NCERT Science book Solution
Reproduction in animals E-Book
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Class 8 Chp9 Reproduction in Animals Science Mission
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Class 8 Reproduction in Human Beings some important topics
Male Reproductive System:
Male Reproductive System:
- The male reproductive germ cell is called sperm. The formation of sperms takes place in the testes.
- The sperms are tiny bodies that consist of mainly genetic material and a long tail that helps them to move towards the female germ-cell.
- Testis is located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than the normal body temperature.
- The testes secrete hormone called testosterone that regulating the formation of sperms and brings about changes in appearance seen in boys at the time of puberty.
- The sperm collected from testis and stored and matured in a tube called epididymis.
- The sperms formed in testis are delivered through the vas deferens (lies inside the penis) which joins a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine.
- Gland like the prostate and the seminal vesicles add their secretions into vas deferens. These secretions convert sperm into a fluid which makes their transport easier. These secretions also provide nutrition to sperms.
- The female germ-cells is known as eggs. Egg cells are made in the ovaries.
- One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube.
- Ovaries ------> oviduct or fallopian tube
- The two oviducts join into an elastic bag-like structure known as the uterus. The uterus opens into the vagina through the cervix.
- The sperms from urethra enter through the vaginal passage during mating and reach to egg cell in the oviduct. This meeting of egg cell to sperm is called fertilization. This fertilized egg is called zygote. Zygote reach to uterus for further development.
- Urethra (penis) ------> sperm ------- > vaginal passage ---- Oviduct ----> egg cell è Fertilization ----> uterus --> placenta
- The zygote gets implanted in the lining of the uterus, and starts dividing to grow into embryo or tinny baby. The cells of embryo divide and differentiate into different types to form tissue. The tissue form organs and slowly became a baby and called foetus.
- The lining of uterus thickens and is richly supplied with blood to nourish the growing embryo.
- The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall.
- Placenta contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
- The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta.
- The rhythmic contractions of the muscles in the uterus help in exchange of food and waste for embryo.
- Inside the uterus embryo is protected by a sac like structure called the amniotic sac which contain amniotic fluid. When baby is ready to born amniotic sac burst, and the wall of uterus contracts to push baby out through vagina.
- The ovary releases one egg every month. If the egg is not fertilized, it lives for about one day and expelled out through vagina.
- At this time , the lining of the uterus thicken with blood for nutrition of embryo slowly breaks and also comes out along with infertile eggs through the vagina as blood and mucous.
- This cycle takes place roughly every month and is known as menstruation. It usually lasts for about two to eight days.
- Twins are formed in two different ways:
- Twins are born due to fertilization of two ova at the same time with sperm. These twins are non identical
- Twins are also born due to division of fertilized egg into two part . These twins are identical.
- Sex is determined at the time of fertilization. A human male has XY sex chromosome and produces two types of sperms, either with X- chromosome or with Y- chromosome.
- A human female has XX- chromosome and produce ova of one type. If the sperm containing X chromosome fuses with ovum , the individual will be girl and the sperm containing Y chromosome fuses with ovum, the individual will be boy.
- Foeticide: The act that cause death of foetus is called Foeticide
- Taboo: A religious custom or practice that restrict certain practice or behaviour like widow marriage. For example Widow marriage was considered as a taboo in India before widow remarriage act pass in 1856.
- Gender role refer to the function performed by boys and girls separately. Society has certain restrictions for what a boys and girl can do. Example Indian girls may encouraged to parents to learn cooking while boys may help in father work.
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