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Reproduction

Reproduction is required for the production of new individuals for the continuity of species.
Reproduction can be classified as asexual or sexual reproduction.

Asexual reproduction results in the production of genetically identical offspring from one parent, without the fusion of gametes.

Sexual reproduction involves the fusion of two gametes to form a zygote, resulting in the production of genetically dissimilar offspring.

Asexual reproduction 

• Beneficial in a stable environment
• Less energy 
• Less time

Sexual reproduction 

• Useful in a changing environment
• Requires more energy
• Requires more time

Cell division

Unicellular organisms, e.g. bacteria, reproduce by binary fission, a form of asexual reproduction.New daughter cells have the same characteristics as parent cells.

In multi-cellular organisms, gametes are produced. The fusion between two gametes results in a combination of genetic material in offspring. New cells formed from sexual reproduction do not have the same characteristics as their parents.

Heredity

Male Gamete/Sperm

• 23 chromosomes
• Large nucleus carries haploid set of chromosomes
• Contains an acrosome. Sac containing enzymes that break down egg membrane
• Middle piece contains numerous mitochondria to provide energy for the sperm to swim
• Has a tail/flagellum which enables movement of the sperm
• It is motile
• Found in testes

Female Gamete/Ovum

• Largest cell in body
• Cannot move by itself
• Found in the ovaries

The Male Reproduction System


Testis

1. Two ovoid testes. The testes produces sperms.
2. Each testes also produces male sex hormones such as testosterone. 
3. The hormones are responsible for development and maintenance of the secondary sexual characteristics.
4. Each testis receives blood from blood vessels in a spermatid cord. 
5. Leading from the end of each testis is a narrow, much coiled tube called the epididymis.The epididymis stores inactive sperms from the testis. 

Scrotum

1. The testes lies between the thighs, in a pair of pouch like sacs called the scrotums or scrotal sacs. 
2. They are outside main body cavity and thus are at a lower temperature than the body.
3. Essential for the sperms development
4. Sperms can only develop at a temperature lower than that of the body.

Sperm duct

1. Each vas deferens, loops over a ureter then open into the urethra.
2. After sperms are released from a testis, they travel through the sperm duct.
3. The seminal vesicle is a g;and that opens into each sperm duct. It stores sperms temporarily before being released into the urethra.

Glands and their secretions

1. Prostate gland, the seminar vesicles and the Cowper's gland secrete a slippery fluid which mixes with sperms.
2. This fluid contains nutrients and enzymes which nourish the sperms and activates them.
3. The mixture of fluid and sperms are called semen.

Urethra

1. Urethra is a tube which both semen and urine pass out from.
2. Semen and urine do not pass through the urethra at the same time. This is because of a circular band of muscle called the sphincter muscle.
3. Sphincter muscle can be controlled to prevent urine from coming out from the bladder during release of the semen or ejaculation.

Penis

1. The tissue in the penis has numerous spaces that can be filled with blood.
2. When this happens, the penis becomes erect and hard.
3. This allows it to enter the vagina of a woman during sexual intercourse to deposit semen containing sperms. 
4. The penis is called a erectile organ. It contains erectile tissue. 

Female Reproduction System

• Two ovoid ovaries produces eggs and female sex hormones such as oestrogen and progesterone. 
• When eggs become mature, they are released.

Oviduct

• Each ovary released mature eggs into an oviduct or fallopian tube.
• Funnel-like opening lying close to the ovary, making it easier for the egg to enter the oviduct.
• The egg is usually fertilized in the oviduct.

• The womb or the uterus is where the fetus or unborn baby develops.
• The uterus is shaped like an upside-down pear.
• It has elastic muscular walls. The smooth muscle tissue in the walls of the uterus contract to push the fetus out during birth.
• The soft, smooth inner lining of the uterus is called the uterine lining or endometrium. 
• It plays a part in embryo implantation. Every month, the endometrium is broken down and it flows out of the body together with some blood.
• It is later build up again.

Vagina

• Leading from the cervix to the outside is the birth canal or vagina. The opening of the vagina is the vulva.
• Semen is deposited in the vagina during mating.

Boys

1. Between 12 to 14 years old
2. Reproductive organs grow in size and start to produce sperms
3. Physical changes

• Body grows rapidly; height increases rapidly
• Body becomes more muscular
• Hair grows on face and body (esp. under armpits and around reproductive orgams)
• Voice breaks

Girls

1. Between 10 to 12 years old
2. Mensuration begins
3. Physical changes

• Height increases rapidly
• Breast grow larger
• Hips become rounder and wider
• Hair grows under armpits and around reproductive organs

Menstrual Cycle 

1. Gonorrhea 

• Pain when passing urine
• Damage reproduction system
• Cause blindness in babies

     2.  Syphilis

• Sores on mouth and reproductive organs
• Deformity in joints, abnormal development of teeth, blindness as well as serious heart and brain problems.
• Baby might have blindness, deafness or even death.

      3. AIDS

• HIV- infected people may develop signs and symptoms such as tiredness, weight loss, fevers and severe diarrhea only after a few months or years.
• Full blown aids occur within eight to ten years of HIV infection
• People suffer from pneumonia, cancer of the blood vessels and damage to the brain