1. SEXUAL REPRODUCTION IN HUMANS
Name : ______________
Class : 9 ___
Day/date: ______________
SEXUAL REPRODUCTION IN HUMANS
MADANIA (Middle School) Grade 9 Biology Handout 1
SEXUAL REPRODUCTION IN HUMANS
25 / 7 / 2011
S1/W2/Handout/G.9/NUR/Biology/
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2. SEXUAL REPRODUCTION IN HUMANS
Compare male and female gametes
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3. The male reproductive system
The testes are the male sex organs that located inside the scrotum. They produce the male gametes or spermatozoa (sperm or sperm cells)
The scrotum keeps the testes at a cooler temperature (< 37 C).
The testes also make the male hormone testosterone (it stimulates changes in a boy’s body as he develops into an adult during puberty (10 – 16 years old).
After puberty, the testes produce sperm cells constantly which are stored in small tubules outside the testes (epydidimis).
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4. The male reproductive system
Sperm duct connects the epydidimis to the urethra.
The prostate gland secrete fluids in which the sperm cells can swim.
Sperm cells and the fluid together form semen (seminal fluid).
The two sperm ducts join with the urethra, which runs down the centre of the penis.
The urethra also carries urine out of the body from the urinary bladder.
A ring of muscle around the urethra contracts to prevent the loss of any urine from the bladder during sexual intercourse.
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5. The female reproductive system
Ovaries are female sex organs that produce the female gametes (ova or eggs).
The ovaries also make the female hormones oestrogen and progesterone, which start to happen during puberty (10 – 15 years old).
Oestrogen stimulates the development of the sex organs
Progesterone prepares the uterus to receive an embryo in the case of a pregnancy.
After puberty, an egg is released from an ovary about every 28 days.
The egg passes out of the ovary and into the openings of the oviduct in a process called ovulation.
The egg moves slowly down the oviduct towards the uterus (womb).
If sperm cells are present in the oviduct the egg will be fertilised. if the egg is not fertilised it will die after about a day.
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6. The female reproductive system
If the egg is fertilised it will divide to form an embryo which may attach itself to the lining of the uterus where it develops into a fetus.
The lower end of the uterus is a cervix (a ring of muscle) that leads to vagina.
Above the vagina is the urethra through which urine from the bladder passes out.
Above the urethra is the sensitive clitoris.
The outer opening of the vagina is called the vulva.
The vagina is sometimes known as the birth canal.
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7. Comparing male and female gametes
Feature
Sperm cell
Egg cell
size
Small
Much larger than sperm cell
Movement
Swims using tails
Moved along the oviduct by cilia and peristalsis (does not move itself)
Food store
Uses sugar in seminal fluid
Protein and fat in cytoplasm
Chromosome 23
Number produced
Millions constantly produced (after puberty) throughout life
One a month after puberty-menopause, except when pregnant or taking the contraceptive pill
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8. Male and female gametes
Gametes are sex cells. The male gamete is called the sperm is a specialised cell that is adapted for swimming. It contain genetic information and chromosomes of the father.
The sperm cell is designed to carry genetic information to the egg.
An egg is much bigger because it provides the food store that support the embryo fertilisation. It contain genetic information and chromosomes of the mother.
An egg is fertilised by the sperm cell. The cell membrane of the sperm cell fuses with the egg cell membrane. The sperm nucleus moves through the cytoplasm of the egg and two nuclei fuse together to form a zygote (fertilised egg)
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9. Male and female gamete
Each sperm cell has mitochondria, which releases energy to power swimming by the tail. The acrosome (the head) contains enzymes are released during fertilisation. These enzyme digest a pathway through the jelly coat surrounding the egg.
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10. Sexual intercourse
During sexual intercourse, males and females stimulate each other.
Blood is pumped into spongy tissue in the penis so that it becomes erect.
This erect penis is placed into the vagina during sexual intercourse.
Fluid made by the walls of the vagina lubricates movement of the penis inside the vagina
This movement stimulates penis and contraction begin in the sperm duct to move sperm from the tubules around the testes towards the penis. At the same time prostate gland also secretes a fluid to form semen or seminal fluid.
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11. Sexual intercourse
Contractions of the urethra move the seminal fluid through the penis into the vagina. This called an ejaculation, at this time the man experiences feelings of pleasure called an orgasm.
Repeated movement of the erect penis against the clitoris or vagina wall may also produce orgasms for the woman
Each ejaculation can contains 500 million sperm cells.
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12. Summary questions
1. Copy and complete the following sentences using the words below:
Semen urethra testes ejaculation prostate sperm cells penis sperm duct scrotum
The male gametes are called __________ and are made in the male sex organs or ____________ which are contained within a sac called the ___________. A tube called the ___________
carries the sperm away from each testes. The _____________
gland adds fluid to the sperm cells to form ____________. During an ________________ the semen passes along the ___________ and out of the erect __________.
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13. Summary questions
Give three differences between sperm cells and egg cells.
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Explain how sperm cells and egg cells are adapted for their functions! _________________________________________
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14. Summary questions
4. Copy out the list organs on the left and match each organ with its correct function from the list on the right Carries urine out of the body __________ A ring of muscle at the opening of the uterus __________ Receives the penis during sexual intercourse __________ Carries the egg from the ovary __________ Produces eggs and female hormones __________ The place where a fetus develops __________ Ovary Vagina Oviduct Cervix Uterus Urethra
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