• involves the fusion of gametes (reproductive cells)

• gamete comes from each parent both parents involved in producing a new life

Where are gametes formed in animals?

In special reproductive organs – gonads

• male gonads (testes) produce sperms

• female gonads (ovaries) produce eggs/ova

Cells in the body = somatic (body) cells + sex cells

How are gametes different from body cells?

• Gametes have haploid number of chromosomes (n); normal body cells have diploid number of chromosomes (2n)

• eg: human body cell has 46 chromosomes; sperm has 23 chromosomes; egg has 23 chromosomes

• when human body cell (46 chromosomes) divides to give gametes (23 chromosomes) process called meiosis

• when human body cell (46 chromosomes) divides to give more human body cells (46 chromosomes) process called mitosis

Why should gametes have a haploid number of chromosomes?

Parts of the Male Reproductive System:

Testis

• two ovoid testes; producing sperms

• produce male sex hormones (testosterone) development and maintenance of secondary sexual characteristics

• testis receives blood from blood vessels in spermatic cord

• end of each testis there is a narrow, much-coiled tube called epididymis stores inactive sperms from testis before they enter sperm duct

Scrotum

• pouch-like sacs; scrotal sacs

• outside main body cavity lower temperature than body essential for proper development of sperms

Parts of the Male Reproductive System:

Sperm duct (vas deferens)

• loops over ureter; opens into urethra

• sperms travel through sperm duct after being released

• gland that opens into each sperm duct

• stores sperms temporarily before they are released through the urethra

Glands and their secretions

• prostrate gland, seminal vesicle & Cowper’s gland secrete slippery fluid that mixes with the sperms

• fluid contains nutrients and enzymes nourish and activate sperms

• mixture of fluid and sperms = semen

Parts of the Male Reproductive System:

Urethra

• tube that passes from bladder, through centre of penis to outside of body

• both semen and urine pass out of body through urethra (but not at the same time) because of sphincter muscle at the base of the urinary bladder that can be controlled to prevent urine coming out during ejaculation

Penis

• tissue in penis has numerous spaces that can be filled with blood

• when filled with blood becomes erect and hard able to enter vagina of woman during sexual intercourse to deposit semen

• erectile organ containing erectile tissue

Head

-about 2.5μm wide

-Large nucleus with small amount of cytoplasm

-Nucleus with haploid set of chromosomes

-Acrosome: sac containing enzymes

- enzyme breaks down part of egg membrane so that sperm can penetrate

Tail

-Beating movement of tail/flagellum enables sperm to swim towards egg

head

middle piece

tail Middle piece

-Numerous mitochondria provide energy for sperm to swim to egg

Sperm (male gamete)

Parts of the Female Reproductive System:

Ovary

• two ovoid ovaries; producing eggs and female sex hormones (oestrogen, progesterone)

• female sex hormones responsible for development and maintenance of secondary sexual characteristics

• when eggs are mature released from ovaries

Oviduct

• each ovary releases mature eggs into an oviduct/fallopian tube

• each oviduct is a narrow, muscular tube leading from ovary to uterus

• funnel-like opening lying close to ovary easier for egg to enter oviduct

• egg usually fertilised in oviduct

Parts of the Female Reproductive System:

Uterus

• where foetus or unborn baby develops during pregnancy

• shaped like an upside down pear; elastic muscular walls; smooth muscle tissue in walls of uterus contract to push fetus out during birth

• soft, smooth inner lining of uterus (uterine lining or endometrium)

• plays a part in embryo implantation

• every month, endometrium breaks down and flows out of body

Zygote fertilised egg cell

fertilised egg cell divides to form a ball of cells

Ball of cells embryo

Parts of the Female Reproductive System:

Cervix

• circular ring of muscle at the lower narrow end of the uterus

• enlarges to allow passage of fetus during birth

Vagina

• leading from cervix to outside

• vagina also called birth canal

• semen is deposited in vagina during mating or sexual intercourse

-About 70000 potential egg cells in ovary

- only about 500 eggs mature

- eggs released from the time of puberty till age of 45-55 in females

Large nucleus one haploid set of chromosomes

Abundant cytoplasm

Covered by cell membrane and outer membrane

Ovum (female gamete)

Puberty is the stage of human growth and development in which a person becomes physically mature.

Body begins to change from child to adult

Girls: ~ 11 years ; Boys: ~ 14 years

During puberty,

-Sex organs mature produce gametes

-Hormones bring about changes in body (secondary sexual characteristics)

-Male sex hormone (testosterone); female sex hormone (oestrogen, progesterone)

Changes during puberty

-Facial hair grows; hair in pubic region and armpits

-Penis, testicles increase in size

-Sperm production begins

-Larynx enlarges, voice deepens

-Hair appears in pubic region and underarms

-Breasts and uterus enlarge; hips broaden

-Menstruation and ovulation start