Transcript Reproduction

Reproduction
Aseuxal reproduction
Sexual reproduction in
plants
Sexual reproduction in
animals
Asexual reproduction
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Binary fission
– Unicellular organisms such as
Amoeba and Paramecium
divide into two by the process
binary fission.
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Budding
– The unicellular fungus Yeast
undergoes budding for asexual
reproduction. However, budding
is different from binaryfission in
that the new part produced is
smaller in size than the parent.
Asexual reproduction in
Angiosperms(Flowering plants)
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Bulb
– e.g. onion, daffodil
– Bulbs are modified shortened, vertical stems surrounded by fleshy scale leaves
with base swollen with food stores.
Corms
– e.g. Gladiolus, Crocus
– Corms are short, erect, swollen underground stems and contain scale leaves but
no fleshy leaves.
Rhizomes
– e.g. ginger, lotus, iris, mint
– Rhizomes contain horizontally growing underground stems and bear nodes,
scale leaves, adventitious roots and axillary buds.
Tuber
– e.g. potatoes, arrowheads
– Tubers are swollen ends of underground stems with numerous axillary buds in
scale leaf scars.
Comparison of the advantages and
disadvantages of vegetative propagation
Advantages
Disadvantages
A rapid way of reproduction
Overcrowding may occurs as
the daughter plants are close to
the parents to cause
competition for space, light as
well as water.
The next generation cannot be
improved the quality because of
no genetic variation. That
decreases the ability to adapt to
changes in the environment.
Diseases will be transmitted to
the offspring from parent plants
rapidly.
Also bad traits will be
transmitted to the daughter
plants.
Desirable traits can be restored
due to offspring are genetically
identical to parents.
Large food reserves are
provided for daughter plants.
The process doesn’t include
external organs or another
plant.
Male reproduction system
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The male reproduction system of human consists of two
testes, sex glands, urethra and penis.
Female reproduction system
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The female reproduction system of human consists of two
ovaries, oviduct, uterus and vagina
Sexual maturity in men and
women
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The sex organs only begin to produce gametes and large amount of sex
hormones at time of sexual maturity which is known as puberty.
Puberty usually begin between the age of 12 and 14. It occurs earlier in
girls than in boys. The sex hormones cause the development of secondary
sexual characteristics which mark out the male from female.
( I ) Secondary sexual characteristics in men:
– Hairs grow on face, under the armpits and around the base of the penis.
– Shoulders broaden and muscles rapidly develop.
– Larynx enlarges and voice becomes lower and coarse.
( II ) Secondary sexual characteristics in women:
– Hairs grow under the armpits and around the vulva.
– Hip girdles broaden.
– Breasts (mammary glands) develop.
– Menstruation starts.
Reproductive cycle
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Ovulation
– For every 28 days only one
ovum is released from one of
the ovaries of the matured
woman. This process is called
Ovulation.
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Thickening of uterine lining
– At the same time, the uterine
lining is thickening by
increasing the cell division and
blood supply, to prepare for the
fertilized egg to implant in.
Reproductive cycle
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Menstruation
– The thickened uterine lining gradually breaks down when there is no
fertilization occurs. The broken cells with a little blood are discharged out of
the body. It is called Menstruation.
Reproductive cycle
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Menstrual cycle
Day 1 to day 4
Menstruation occurs and lasts for about 4 days.
Day 4 to day 14
Follicle with an ovum develops inside the ovary.
The follicle secretes a female sex hormone. It
stimulates the thickening of uterine lining to
prepare for the implantation of the fertilized ovum.
On the 14th day the follicle bursts to release the
ovum—ovulation.
The body temperature is slightly lower than normal.
After ovulation, the empty follicle develops into the
yellow body (corpus
luteum). The yellow body secretes another female
sex hormone. This hormone stimulates further
thickening of the uterine lining. If implantation
succeeds, the uterine lining continuously thickens
until the placenta is formed. No menstruation
occurs during pregnancy. If the ovum is not
fertilized within 36 hours after ovulation, it will die.
In addition, the yellow body degenerates and the
hormone level drops. It causes menstruation on
the 28th day.
Day 14 to day 28
Transfer of semen and
fertilization
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During sexual intercourse, the dilation of the arterioles in penis increases
the turgidity of its erectile tissues. The erect penis is inserted into the
vagina of the female.
Process
– The muscular contraction of the epididymis and sperm duct cause the
ejaculation of about 5 ml of semen through the urethra into vagina.
– Each ejaculation may introduce about 300-500 millions of sperms. Such
large number of sperms is produced to increase the chance of fertilization.
The sperms remain alive from 1 to 3 days in the female reproductive tract.
– The sperms use their tails to swim from the vagina through the cervix and
the uterus to the oviduct.
– Their environment is also assisted by the muscular contraction of the uterus
and oviduct.
– Only the nucleus of one sperm can enter the ovum to fuse with her nucleus
to form a diploid Zygote. It is called Fertilization. Once fertilization occurs,
other sperms cannot pass through the egg membrane of the ovum.
Mammalian embryo
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Implantation
– A zygote formed by fusion of the egg and sperm moves slowly down the
oviduct to the uterus and divides to form an embryo. The embryo embeds
within the uterine lining for development.
Mammalian embryo
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Amnion covers the embryo and
secretes amniotic fluid.
Amniotic fluid acts as a shock
absorber, protects the embryo
from mechanical shock, prevents
the embryo from becoming
desiccated and allows it some
freedom of movement.
Placenta connect the embryo to
the wall of the uterus in order to
supply the nutrients and oxygen
to the embryo and remove the
wastes (CO2, urea).
Umbilical cord transports the
blood between the embryo and
the placenta for exchange of food
and wastes.
Development of embryo to form a
foetus is called gestation.
Parturition
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Before birth of the foetus, the
position of the foetus alters so
that it lies head downward near
the opening of the cervix.
When birth the muscles in the
wall of uterus contract
rhythmically to push the baby out
of mother through the cervix.
After birth the baby is still
attached to the placenta by the
umbilical cord. The umbilical
cord is tied and cut that the scar
becomes the navel. The placenta
detaches from the uterine wall to
become afterbirth.
Birth control
Contraception methods
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Natural method
– Women should have
intercourse during safe period
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Contraceptive pills
– Combined pill ¡Vcontains
oestrogen and progesterone
– Mini-pill ¡Vcontains only
progesterone
Birth control
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Barrier method
– Condom
– Diaphragm
Birth control
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Surgical method sterilization
– A permanent method of birth
control and irreversible.
Vesectomy
Tubal ligation
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Intrauterine devices IUD
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