• In sexual reproduction, two gametes or germs cells, i.e. the male gamete called sperm and the female gamete called ovum, are involved.
• Both the sperm and ovum fuse together to form a zygotes which develops into a new individual.
Sexual reproduction in flowering plants
A flower is the reproductive organ in angiosperms
Point of attachment.
• It is an enlarged, flattened tip of the stalk.
• Petals and other parts arise from the thalamus.
• Outermost whorl of the flower which is made up of petals.
• The calyx protects in the inner parts of the flower in their bud stage.
• Second whorl of the flower which is made up of petals.
• Helps flowers in attracting insects to carry out pollination.
• Third whorl and the male organ of the flower.
• Consists of stamens.
• Each stamen is made of the filament and anther.
• Anthers store pollegrains.
• Innermost whorl and the female reproductive organ.
• Consists of pistil or carpels.
• Carpels is made of stigma, style and ovary.
Pollination is the transfer of pollens from the anther to the stigma of the same plant or a different plant of the same species.
Type of pollination
- Self –pollination: The transfer of pollen grains from the anther to the same flower.
- Cross –pollination: The transfer of pollen grains from the anther of one flower to the stigma of another flower of the same species.
Different agents help to bring about cross pollination. They are insects, wind, water, etc.
• The process of fusions of the male gamete to form a zygote is called fertilization.
• When pollen grains setttle on the stigma, they from a tube called pollen tube.
• The pollen tube grows through the style of the foiwer and the enters ovary.
• The tip of the pollen tube dissolves to release the pollen grain into the ovary.
In the ovary, a female gamete fuses with the pollen grain to form to a zygote.
Fruit and seed formation
• After fertilization, the ovary enlarges and forms a fruit.
• Scientifically, the fruit is the ripened ovary.
• Ovules become the seeds of the fruit.
• All parts other than the ovary dry up and fall off.
• Tomato , lady’s finger and brinjal are all fruits.
Reproduction in human beings
Growth and development
• Growth and development are gradual and processes.
• Size and complexity of the body increase gradually.
Growth in humans is divide into the following stages.
- Infant: children between 1 month and 1 year of age are called infants.
- Toddler: a) children between 1 to 4years of age.
b) Growth is fast.
c) children learn to balance the body.
- Adolescent: children between the age of 11 to 19 years.
The period of transition from childhood to adulthood is called adolescence.
- Adulthood: It is from the age of 18 years onwards.
An individual attains full growth and emotional stability.
Career and shouldering responsibilities are priorities.
• Puberty is period during which the reproductive system matures in boys and girls.
• In girls, puberty beings at the age of 11 years.
• In boys, it beings at the age of 12-14years.
• Puberty continues till the age of 18 years.
Changes which occur at the time of puberty
Changes in boys
• Tests mature and start producing sperms.
• Pectoral girdle [shoulder girdle] grows.
• Hair growth in the pubic region.
The skin in the pubic region becomes darker.
• Development of moustache and beard.
• Development of a deep voice.
Changes in girls
• Ovaries mature and start producing ovum. The menstrual cycle beings.
• Pelvic girdle [hip girdle] becomes board.
• hair growth in the pubic region.
• the Skin in the pubic region becomes darker
• Enlargement of breasts.
• the voice becomes shrill.
Problems related to adolescence
• Adolescence is a period of physical, mental and emotional changes.
• The spurt of growth in certain body parts create confusion in teenagers. * They start worrying about it. They start feeling lonely do not feel comfortable to share their problems with others.
• Teenagers becomes highly sensitive about someone’s opinion.
• They tend to become angryor upset very easily.
• They prefer company of the person of their own age.
• Due to hormonal changes , they experience dipression.
• They feel the urge to become independent but are unsure about.
• They have many questions about sex.
• This makes it an important to counsel them in the right.
Male reproductive system:
- Testes (testicles) : a pair of testes is locted below the abdomen in the scrotal sac or scrotum
• The testes produce male gametes or sperms (germs cells).
• The maintain the temperature 2-3C below the body
• Temperature the scrotum is located outside the body cavity.
- Epididymis : tubes presents in the testes joint form the epididymis.
• The epididymis stores sperms temporarily.
- Vas deferens (sperm duct) : each epididymis continues further as the sperm duct or vas deferens.
• Each vas deferens unites with a tube coming from the urinary bladder on either side.
• Thus, the urethra is the common passage for sperms and urine.
- Seminal vesicales : the seminal vesical produce a secretion which is responsible for the transport of sperms.
- Prostate gland : it is biolobed structure which appear surrounds the urethra. It pours alkaline secretion into the semen.
- Cowper’s gland : these are two small ovoid glands.
• They open the urethra.
• Their secretion serves as a lubricant.
- Penis : the urethra passes through the penis.
• It carries either urine or semen at a time.
Female reproductive system
- Ovaries: two ovaries are presents in the pelvic cavity, one on each side of the uterus.
• Ovaries produce ova which are female gametes.
• One ovum is released by one ovary every month
- Oviduct (fallopian tube) : two oviduct or fallopian tubes are presents each close to one ovary of its side.
• When the egg is released by the ovary, it passes down to the uterus through the oviduct.
- Uterus (womb) : the uterus is a hollow pear-shaped, muscular organ.
• The inner lining of the uterus called endothelium protects and nourishes the developing embryo.
- Vagina (birth canal) : the uterus open into the vagina.
• The vagina is a muscular, narrow tube.
- Vulva : the vagina and urethra both open into the vulva.
• If fertilization take place
Fertilization occurs in the oviduct.
All the time of intercourse, semen is deposited into the female’s vagina.
• Sperms swim through the uterus and reach the oviduct.
• A single sperms fuses with the ovum and forms the zygote. This completes the process of fertilization.
• As soon as the zygote is formed, it starts developing.
• By the time it reaches the uterus, it is a mass of cells known as an embryo.
• It remains attached to the wall of the uterus throughout it development.
• The period of development of the embryo inside the uterus is called the gestation period .
• In human, the gestation period is of month, I.e. about 280 days.
• The embryo after completing three month of development is called the foetus.
• The placenta is a special tissue which provides food and oxygen to the foetus.
If there is no fertilization
• If the ovum is not fertilised , then it lives for one day the lining of the uterus breakdown and disintegrates.
The ovum lining of the uterus and some blood are discharged out of the body. This is called mensuration.
• The menstrual discharged lasts for four days.
• After menstruation, the ovum is released, and the uterus again prepare itself for the receival of the fertilized egg cell.
• If there is no fertilization, the menstruation is repeated.
Sexually transmitted diseases
- Gonorrhoea : caused by bacteria.
- Syphilis : bacteria spread through sexual contact.
• Burning sensation during urination.
• Urethral discharge containing pus.
Sores in genitals.
• Both diseases are curable.
- Aids (acquired Immunodeficiency syndrome) : aids is caused by the infection of HIV (human immunodeficiency virus).
• This virus attack the immune system itself.
• HIV penetrates the T- lymphocytes.
• Reduction in the number of T- cells reduces the immunity of a persons.
• HIV is transmitted by
sharing contaminated needles
Blood transfusion of contaminated blood.
• From the infected mother to the unborn foetus.
• To creates awareness about the severity of aids and protection from HIV, THE 1 of December is world aids day.
DIFFERENT METHODS ARE AVAIABLE IN ORDER TO PREVENT PREGNANCY:
- Hormonal method:
Various hormonal preparation come in the form of tablets or pills, commonly called contraceptive pills.
- Barriers methods:
• Condoms, diaphragms, and spermicidals are used.
• Condoms are used by males while diaphragms and spermicidals are used by females.
- Intra-uterine devices (IUDs):
IUDs such as lippe’s loop and copper – t are fitted in the uterus. They prevent fertilization.
- Surgical methods:
In females, the fallopian tubes are ligated. This is called tubectomy.
In males, the deferntia are ligated. This is called vasectomy.
- Induced abortion:
It is also known as medical termination of pregnancy (MTP).
• If a woman becomes pregnant and the couple is not willing to have h baby, then the option of induced abortion is chosen.