Form 3 Science Chapter 4 Reproduction

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FORM 3 SCIENCE NOTES
CHAPTER 4 REPRODUCTION
4.1 Sexual and Asexual Reproduction
 Reproduction 繁殖 – The production of new individuals from living organisms.
 Reproduction increases number of individuals of same species and replaces those that die.
 It ensures that organisms do not become extinct.
Sexual reproduction
 Involves two parents of different sexes.
 It involves fusion 合成 of sex cells.
 Two types of fertilisation: External fertilisation, Internal fertilisation
 External fertilisation – Nucleus of male gamete fuses with nucleus of female gamete outside body of
female organism. (Aquatic animals)
 Internal fertilisation – Nucleus of male gamete fuses with nucleus of female gamete inside the body of
female organism. (Mammals, birds, reptiles and insects)
* Chromosome 染色体: Thread-like structure of nuclei acids and protein found in nucleus of most living
cells, carrying genetic information in form of genes 基因.
Male gamete
雄性配子
Fertilisation
Zygote 合子
Development
New
individual
with
variations
GrowthFemale gamete
雌性配子
Sexual reproduction

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Asexual reproduction
 Involves only one parent and does not involve sex cells.
 Fertilisation of gametes does not take place.
 New individuals formed are identical to parent and have same genetic materials as their parent.
 Advantage – Requires only one individual.
 Disadvantage – No variation of characteristics in new individuals.
 Carries out by lower level animals 低等动物 (Amoeba, Paramecium, Hydra) and plants (onion, ginger,
mosses and algae)
Types of asexual reproduction:
 Binary fission 二分裂
- Division of single parent cell into two identical daughter cells.
- Nucleus divides first followed by cytoplasm.
- Examples: Amoeba, Paramecium
 Regeneration 再生
- Fragments 片段 from parent organism grow and develop into completely new individuals.
- Examples: Flatworms, starfish
New cells
Development New
individual
Growth
Parent
Asexual reproduction

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 Budding 发芽生殖
- Formation of buds at the side of parent organism.
- Bud starts off as a swelling which grows to resemble 相像 the parent.
- Mature bud then drops off to become new individual
- Examples: Hydra, yeast
 Spore 孢子 formation
- Formed by cell division in special structures called sporangia 孢子囊 (singular: sporangium).
- Mature sporangium bursts open to release mature spores.
- Spores are small and light and easily carried by wind to far places.
- Example: Fungi, non-flowering plants such as mosses and ferns
 Vegetative reproduction 营养繁殖
- New plants are formed form structures of plant other than flowers.
- Examples: Ginger, onion, potato

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Difference between sexual and asexual reproduction
Sexual reproduction Aspect Asexual reproduction
Two Parent(s) One
Involve gamete Gametes Does not involve gamete
Fertilisation occurs to form zygote Fertilisation Fertilisation does not occur
Higher level organisms Organisms Lower level organisms
Different from the parents Offspring produced Resemble the parents
4.2 The Male Reproductive System
Structure and function of the different parts of the male reproductive system
Structure Function
Testes 睾丸 (singular: testis)  Produce sperms
Scrotum 阴囊
 Holds testes outside the body
 Protects testes
Penis 阴茎  Ejaculates sperms into vagina during sexual intercourse
Epididymis 附睾  Stores sperms
Sperm ducts (vas deferens)
输精管
 Transports sperms produced in testis to urethra
Urethra
 Transports sperms in semen 精液 outside the body
 Transports urine from bladder out of body (does not involve
reproduction)
Seminal vesicle 精囊  Secretes fluid that provides nutrients to sperms
Prostate gland 前列腺  Secretes fluid that neutralises the acidity of urine and female vagina
Front view of male reproductive system

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Structure and function of sperms
 Sperms are male gametes.
 Sperm is the smallest cell in the body (0.01-0.05 mm long) and shaped like a tadpole.
Parts of sperm Function
Head
 Contains a large nucleus which carries genetic materials.
 Penetrates 穿透 membrane of ovum during fertilisation.
Neck (Middle piece)
 Contains mitochondria 线粒体 which provide energy for sperm to swim
towards Fallopian tube in female reproductive system.
Tail
 Beating of tail enables sperm to swim to meet ovum in the female
reproductive system.
Changes in males during puberty
 Puberty – Stage when boys and girls become sexually mature.
 Usually starts at about 15 years old for boys.
 Puberty is accompanied by physical, physiological 生理 and emotional changes.
 Changes that occur:
- Growth of hair on face (beard, moustache) and body (chest, armpits, pubic region).
- Voice box (larynx) enlarges.
- Body becomes more muscular.
- Rapid growth of long bones to increase height.
- Production of sperm by testes.
- Penis, scrotum and prostate become larger.
- Certain mental and emotional changes (greater interest in females).
Human sperm

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4.3 Female Reproductive System
Structure and function of the different parts of the female reproductive system
Structure Function
Ovary 卵巢  Produce ovum (egg)
Fallopian tube / Oviduct 输卵管  Carries ovum from ovary to uterus
Uterus / Womb 子宫  Place where embryo 胚胎 develops
Cervix 子宫颈
 Secretes mucus that enhances sperm movement into uterus
 Prevents large foreign bodies from entering uterus
Vagina 阴道
 Place where sperms are deposited
 Birth canal
Structure and function of ovum
 The female gamete is ovum (plural: ova).
 Largest cell in human body (about 0.1 mm in diameter) and cannot move by itself.
 Role of ovum in reproduction:
- Carries genetic materials from mother in nucleus.
- During fertilisation, nucleus of ovum combines with nucleus of sperm to form zygote which
develops into new offspring.
Front view of female reproductive system
Cytoplasm (contains food substances)
Jelly layer (for protection)
Nucleus (contains genetic materials)
Structure of human ovum

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Characteristic Sperm Ovum
Size 0.01-0.05 mm 0.1 mm
Place of production Testis Ovary
Mobility Able to move by itself Unable to move by itself
Number produced Millions in a day One released every 28 days
Lifespan About 72 hours About 24 hours
Differences between sperm and ovum
Changes in females during puberty
 Females usually reach puberty earlier than males at about 11-13 years.
 Changes that occur:
- Ovaries start to release mature ova and produce sex hormones.
- Breasts develop and hips become wider.
- Hair begins to grow in armpits and pubic area.
- Menstruation begins.
- Mental and emotional changes (Shy and greater interest in males).
4.4 The Menstrual Cycle
Menstrual phase 月经期
Lining of uterine wall
together with blood vessels
break down. Lining tissues
and blood are discharged as
menstruation occurs.
Repair phase 滤泡期
Lining of uterine wall
builds up and becomes
thicker and richer in
blood vessels.
Premenstrual phase 黄体期
 Uterine wall continues to
thicken and becomes rich in
blood vessels in preparation
for fertilisation.
 It is ready for implantation.
 If fertilisation is not
successful, lining of uterus
starts to break down and
another cycle starts.
Fertile phase 排卵期
 Ovulation usually occurs on
the 14th
day.
 Uterine wall and blood
vessels continue to develop.

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 Menstrual cycle 月经周期 is the repeated cycle of events from puberty (when ovum production begins)
to menopause 更年期 (when ovum production stops).
 At puberty, ova ripen at different times. When ovum ripens and matures, it is released from ovary.
 Ovulation 排卵 – Release of one mature ovum from one of the two ovaries into Fallopian tube
during fertile phase.
 On its journey to uterus, the ovum is ready for fertilisation 受精.
 Changes take place in uterus to prepare for development of foetus 胎儿 if the released ovum is
fertilised.
 Lining of uterine wall 子宫壁 becomes thicker and has more blood vessels. This is to prepare the
uterus for implantation 植入 of fertilised ovum.
 If there is no fertilisation of the ovum:
- Lining on wall of uterus and blood vessel start to break down.
- Ovum, blood and lining of uterine wall are discharged through vagina.
- This is called menstruation 月经 (sometimes referred as ‘period’).
 Menstrual cycle:
- Lasts for about 28 days (may vary)
- Length of cycle maybe affected by mental condition, physical activity, emotional changes and
nutrition of an individual.
 A woman may experience premenstrual syndrome 经前综合症.
- Effects: Abdominal pain, emotional changes, headaches and lethargy 昏睡
 Personal cleanliness and hygiene are important during menstruation. Being hygienic prevents
infections of reproductive organs.
 Women stop menstruating at about 50 to 55 years old. This stage marks the end of their fertility 生育
能力 and is called menopause.
4.5 Fertilisation and Pregnancy
Fertilisation
 Human reproduction begins with sexual intercourse 性交 or copulation.
 During sexual intercourse, millions of sperms are released from penis of male into vagina of female.
However, only about 100 will reach the oviduct and only one sperm fertilises the ovum.
 Sperms swim with the help of their tails from vagina through cervix. They then enter the uterus and go
up the Fallopian tubes.
 If a mature ovum is present in oviduct, sperms will surround the ovum.
 Only one sperm will successfully penetrate the membrane 膜 of ovum.
 Head of sperm enters the ovum. Its tail is left outside.
 A membrane is formed immediately around the ovum. This membrane prevents other sperm from
entering the ovum.
 Nucleus in head of sperm fuses with nucleus of ovum.
 The fusion between sperm and ovum forms a zygote. This process is called fertilisation.

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Development of an embryo into a foetus until birth
 Ovulation
- Mature ovum is released into oviduct.
 Fertilisation
- Fusion of nuclei of sperm and ovum form zygote.
 Development of zygote
- Zygote divides into two cells (cell division 细胞分裂) after 30 minutes. The cells divide repeatedly
to form a ball of cells called embryo.
- Embryo moves down the oviduct and enters uterus. Movement of embryo is assisted by rippling
movements of uterine wall.
 Implantation
- On reaching the uterus (about 7-8 days after fertilisation), embryo implants itself into the
thickened lining of uterus.
- It sinks into the soft tissues of uterine wall.
- Cells of the implanted embryo continue to divide many times.
Sequence of ovulation, fertilisation and implantation
of embryo inside the uterus of female
Zygote Embryo Foetus Baby
Repeated
cell
division
Cell
division
Specialisation
of cells to
form organs
and systems
Result of
fertilisation
between
male and
female
gametes
A ball of
cells for
about two
months
After two
months,
embryo
develops and
resembles a
human being
Fully
developed
at birth
Pregnancy

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 Development of embryo
- Embryo that is implanted in uterine wall continues to grow inside a sac 囊 called amnion 羊膜.
Foetus is surrounded by amniotic fluid 羊水.
- Embryo gets nutrients and O2 from blood vessels in uterine lining.
- Finger-like projections grow from the embryo into lining of uterus. This eventually forms the
placenta 胎盘.
 Development of foetus
- Foetus is joined by umbilical cord 脐带 to placenta.
- Umbilical vein: Carries blood rich in nutrients and O2 from placenta to foetus.
- Umbilical artery: Carries waste products such as urea and CO2 away from the foetus to placenta.
These substances diffuse into mother’s blood.
- Foetus starts to move.
- When foetus is fully formed at the end of pregnancy, the foetus rotates its body until the head
points towards the cervix.
 Birth of baby
- At about 9 months, the baby is ready to be born.
- Expectant mother 准妈妈（即将分娩的女人） starts to feel small contractions in uterine wall.
- Amnion breaks and amniotic fluid flows out.
- Uterine muscles contract very strongly to push the baby out through cervix and vagina.
4.6 The Importance of Prenatal Care
 Foetus growing inside its mother’s womb depends on its mother for food.
 Pregnant mother need a balanced diet and also enough nutritious food for foetus to grow normally
and be healthy.
 Balanced diet is one which contains right amounts of all seven classes of food.
 A pregnant woman requires more energy a day than a woman who is not pregnant.
Nutrient Pregnant woman Woman who is not pregnant
Protein (g) 102 70
Iron (mg) 15 10
Calcium (mg) 1 000 – 1 500 800
Vitamin A (µg) 900 750
Vitamin C (mg) 100 70
Nutrient requirements of pregnant woman and woman who is not pregnant

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 Pregnant woman should have enough rest and sleep
 She should not take drugs which are not prescribed by doctor, drink alcohol, smoke cigarettes
because these activities can harm the foetus.
 Pregnant woman who smoke may have:
- Smaller babies
- Stillborn babies 死产（胎死腹中）
- Babies who are mentally and physically retarded 智力 / 身体迟钝
- Miscarriages 流产 or premature babies 早产儿
 CO is found in cigarette smoke. When CO is inhaled by pregnant woman, it will combine with
haemoglobin and form carboxyhaemoglobin 碳氧血红蛋白.
- Less O2 is transported to foetus and may cause abnormal development of foetus’ brain.
 If a pregnant woman drinks excessive alcohol, the alcohol is transported by blood to foetus. This
results in foetal alcohol syndrome 胎儿酒精谱系障碍. Alcohol slows down the development of foetus,
damages its brain, nervous system and heart.
 Pregnant woman should go for regular check-ups by her doctor.
 Some babies are born without complete limbs. They are victims of side effects of Thalidomide. Their
mothers had taken this drug for nausea during their pregnancy without knowing their side effects.
4.7 The Importance of Research in Human Reproduction
 Two main issues concerning human reproduction:
- Sterility 不育症
- Birth control
 Advancement of science and technology has helped to overcome these problems.
Sterility
 Sterility – Inability to produce children.
 Causes of sterility in females:
- Defective reproductive organs
- Blocked Fallopian tube
- Fertilised egg cannot implant itself in uterine lining
 Causes of sterility in males:
- Low sperm count
- Deformed or weak sperms
- Inactive sperms
Thalidomide pills
An infant with birth abnormality
from Thalidomide

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Methods to overcome sterility
 Nutrition
- Consume nutritious food and abstain from smoking and drinking alcohol.
 Drug treatment
- Take hormone pills or injections to enhance ovulation (female) or increase chances to produce
more active sperms (male).
 Surgery
- Removal of growth tissues in oviducts which cause blockage or growth in uterus which prevents
implantation.
 In vitro fertilisation (IVF) 体外人工授精
- Fertilisation takes place outside body. This method is used to make test-tube babies 试管婴儿 and
is recommended for females with blocked oviducts.
Birth control (Contraception)
 Birth control basically means preventing pregnancy by:
- Stopping production of eggs (ovulation)
- Stopping sperms from reaching and fertilising ovum
- Stopping implantation of embryo in uterus
 Birth control methods can be natural, mechanical, hormonal, chemical or surgical.
Embryo transfer in IVF method

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Method Mode of action Advantage Disadvantage
Rhythm
(Natural)
Using cervical mucus
changes and body
temperature measurements
to estimate the time of
ovulation and avoiding
intercourse during fertile
period.
 Natural
 No cost
 No medical or
hormone side effects
 Acceptable to most
religions
 Unreliable
 Requires ongoing,
accurate record
keeping of fertile
period
Condom
(Mechanical)
避孕套
Thin, disposable latex
sheath placed over penis
prior to intercourse to
prevent sperm from
entering vagina.
 No side effects
 Gives some protection
against sexually
transmitted diseases
(STDs) including
Human
Immunodeficiency
Virus (HIV)
 Slight decreased
sensation for male
 Can break or leak
 Latex allergies
Intrauterine
contraceptive
device (IUCD)
(Mechanical)
子宫环
Small plastic or copper
device that is placed into
the uterus by a doctor to
prevent implantation.
 Provides protection
for 8-10 years
 Increases menstrual
flow
 Does not protect
against STDs
 Cramps
Contraceptive
pills
(Hormonal)
避孕药
Pills containing specific
hormones which prevent
ovulation
 Reliable if taken
regularly
 Makes monthly period
more regular
 Lowers the risks of
ovarian cancer and
endometrial cancer
 May cause side effects
such as nausea and
weight gain
 Does not protect
against STDs
Spermicides
(Chemical)
杀精剂
Foams, jellies or creams
placed in vagina prior to
intercourse that chemically
kill sperms
 Inexpensive
 Can be used with
condoms
 Messy to use
 May cause allergies
Diaphragm 避
孕隔膜 with
spermicide
(Mechanical
and chemical)
Dome-shaped rubber disk
with a flexible rim that
covers cervix so that sperm
cannot reach the uterus.
Spermicide is applied to
diaphragm before insertion.
 Can be inserted a few
hours before
intercourse
 Does not protect
against STDs
 Must be fitted by a
doctor and training is
required to fit
 May cause abdominal
pain

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Injection
针剂 (Depo-
Provera)
(Hormonal)
Injection of specific
hormone progestin that
inhibits ovulation, prevents
sperm from reaching the
egg and prevents the
fertilised egg from
implanting the uterus.
 Only one injection
every 3 months
 Irregular bleeding
 Weight gain
 Breast tenderness
 Headaches
 Does not protect
against STDs
Vasectomy
输精管结扎术
(Surgical)
Sperm ducts are cut and
tied to prevent sperms from
leaving the ducts.
 Most reliable method
 No hormonal side
effects
 Requires surgery
 Operation can rarely
be reversed
Ligation
输卵管结扎术
(Surgical)
Fallopian tubes are cut and
tied to prevent ovum from
leaving the tubes.
 Most reliable method
 No hormonal side
effects
 Requires surgery
 Operation can rarely
be reversed
Vasectomy Ligation IUCD

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4.8 Sexual Reproductive System of Flowering Plants
 Flowering plants reproduce by sexual reproduction.
 Flower is important in reproductive system of plant.
 Flowers produce male and female gametes and produce seeds which grow into new plant.
- Some flowers are bisexual 双性 (have male and female reproductive organs)
- Some are unisexual 单性 (Either male of female)
The structure and function of the flower
Part Function
Sepal 萼片 Encloses and protects flower during bud stage
Petal 花瓣 Attracts insects to pollinate 授粉 flower
Stamen
雄蕊
Anther 花药 Produce pollen grains 花粉
Filament 花丝 Positions anther so that pollen grains are exposed and can be pollinated by agents
Pistil
雌蕊
Stigma 柱头 Receives pollen grains
Style 花柱 Positions stigma to receive pollen grains
Ovary 子房 Contains ovule (ovules)
Ovule 胚珠 Contains female gametes
Function of different parts of flower
Structure of flower

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4.9 Pollination
 Pollination – Transfer of mature pollen grains from anther to stigma.
- When anther of flower is mature, it bursts open and pollen grains are exposed.
- Pollen grains may fall to ground or carried away by pollinating agents.
 Pollinating agents – Media which help in transfer of pollen from anther to stigma.
Pollinating agents Examples
Insects Flame of the forest 紫矿, rose, sunflower, hibiscus
Animals Durian (bats, African tulip (birds)
Wind Grass, paddy plant, maize
Water Hydrilla 黑藻, water lily, water hyacinth
Pollinating agents
Pollinating agents
 Insects
- Insects suck nectar and collect pollen grains from flowers. Pollen grains stick to their bodies and
legs, and are transferred onto the stigma of same or next flower.
- Characteristics:
 Big and colourful flowers with short flower stalks
 Produce nectar and are scented 香
 Short filaments and small anthers
 Short styles and stigmas with sticky surfaces
 Produce small quantities of pollen grains, which are large, sticky and have rough surfaces
 Animals
- Pollen grains stick to beaks, feathers or fur of animals and are transferred to stigma of flower.
- Characteristics:
 (Similar to those pollinated by insects)
Structure of stamen Structure of anther Structure of ovary

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 Wind
- For most of the monocotyledonous plants 单子叶
- Wind blows and carries pollen grains from anthers to stigma
- A lot of pollen may be wasted when they land on ground
- Characteristics:
 Small, not brightly coloured and have long stalks
 Do not produce nectar and are not scented
 Anthers and stigma hang outside the flowers and are exposed to the wind
 Long filaments with large anthers hang outside flowers and sway in wind
 Anthers produce large quantities of pollen which are small, light and smooth
 Style and stigma are long. Stigma is long and feathery to trap pollen grains blown by wind
 Water
- Characteristics:
 Large amounts of pollen are produced
 Pollen grains are light and can float on water and do not rot easily
Characteristics Pollinated by insects Pollinated by wind
Petals Large and brightly coloured Smaller and not brightly coloured
Pollen grains Small quantities, large, sticky and rough Large quantities, powdery and smooth
Stigma Sticky Large and feathery
Stigma and
anther
Located in the flower Hang outside the flower
Nectar Produce nectar No nectar
Smell Scented No scent
Characteristics of flowers pollinated by insects and wind
Self-pollination and cross-pollination
 Self-pollination 自花授粉 – Transfer of pollen grains from anther of one flower to stigma of same
flower or stigma of another flower on the same plant
 Cross-pollination 异花授粉 – Transfer of pollen grains from anther of one flower to stigma of
another flower of different plant of same species
Cross-pollination

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Self-pollination Characteristics Cross-pollination
One plant Number of plants Two plants of the same species
One or two flowers (on the same
plant)
Number of flowers Two flowers
Anther and stigma must mature
at the same time (One flower)
Anther and stigma may mature at
different times (Two flowers)
Anther and stigma
Anther and stigma of two flowers
mature at same or different times
No variation in young plants Variations More variations
Characteristics of self-pollination and cross-pollination
 Cross-pollination has more advantages than self-pollination:
- Enables genetic materials from two different plants of same species combine. Young plant inherits
继承 characteristics from both parent plants.
- Results in new varieties which may inherit good characteristics from both parents:
 Healthier plant (more resistant to diseases and insects)
 Ability to adapt to changing environment
 More abundant 丰富 and better quality fruits
 Better quality seeds
 Mature earlier and produce fruits faster
Self-pollination

19. 19
Use of cross-pollination in agriculture
 Agricultural agencies in Malaysia that are responsible for carrying out research into cross-pollination:
- Malaysia Agriculture Research and Development Institute (MARDI)
- Malaysian Palm Oil Board (MPOB)
 Aim: To produce better quality agricultural products
 Example of results:
- Cross between two palm oil species (Dura and Pisifera) resulted in new species called Tenera
(produce higher yield 产量 and better quality palm oil)
- New variety of paddy plant like MR103 and MR106 (produce better quality rice grains)
4.10 Development of Fruits and Seeds in Plants
 After pollination, fertilisation takes place.
 Fertilisation – Fusion of male and female gametes. It occurs in ovule inside the ovary of flower.
Fertilisation
 When pollen lands on sticky surface of stigma, sugary secretion 分泌物 on stigma stimulates the
germination 发芽 of pollen.
 Pollen tube 花粉管 is formed and it grows downwards through style towards ovule inside ovary.
 Then, formation of fruits and seeds occurs.
Germination of pollen grain
Fertilisation in plants

20. 20
 Fertilisation in plants:
- Pollen grain lands on stigma.
- Pollen grain germinates and develops a pollen tube.
- Pollen tube grows down the style towards ovary.
- Pollen tube grows through the micropyle 珠孔 and the tip of the tube bursts to releases male
gametes.
- Male gamete enters ovule and fuses with female gamete to form zygote.
The formation of fruits and seeds
 Zygote undergoes cell division and develops into embryo.
 Embryo is made up of plumule 胚芽, radicle 胚根 and cotyledons 子叶.
Flowers parts After fertilisation
Ovum Zygote  Embryo
Ovule Seed
Ovary Fruit
Ovule wall Testa 种皮 of seed
Ovary wall Wall of fruit
Stigma, style Become smaller, dry up and drop off, or may remain to help in dispersal 分散
Stamens Wither and drop off
Sepals, petals Wither and drop off
Changes that occur to flower after fertilisation
4.11 The Germination of Seeds
 Seed has supply of food stored inside it. It is the dormant 休眠 part of plant.
 When it falls on suitable soil, it germinates and grows into new plant.
The structure and function of a seed
 A seed is covered by external seed coat called testa.
 Hilum 肺门 and micropyle are outside the seed.
 When a seed is cut open, the embryo, which includes cotyledons and endosperm 胚乳 (only in
monocotyledonous seeds), can be seen.

21. 21
Part Structure Function
Seed coat
Testa Protects seed and embryo inside
Hilum Place where seed is attached to fruit
Micropyle Tiny pore which allows air and water to enter into seed.
Embryo
Plumule Part of embryo which develops into the shoots of plant
Radicle Part of embryo which form root of plant
Cotyledon
Contains stored food like carbohydrates (starch) to supply to seedling
during germination
Endosperm Contains stored food to supply to embryo during germination of seed
Structures of seed and their functions
Physical changes in seedlings during germination
 Germination – Stages of growth of seed, spore or pollen grain.
 When seed is in soil, it absorbs water from soil through micropyle.
 Water softens testa.
 Cotyledons expand and testa bursts open.
 Radicle and plumule emerge 出现. Radicle grows downwards into soil to form root and plumule
grow upwards through soil to form shoot.
* Radicle  Root, Plumule  Shoot
 Food needed for growth of radicle and plumule is obtained from food store in cotyledons or
endosperm.
 When stored food in cotyledons is used up, cotyledons drop off.
 Seedling continues to absorb food from food store until first green leaves emerge.
 Young green leaves of seedling start to produce food by photosynthesis before all food store is used
up.
Structure of seeds

22. 22
The conditions necessary for germination of seeds
Factor Importance
Water
 Softens the testa to enable the radicle and plumule to grow out
 Allow diffusion of gases
 Medium for enzyme action to convert stored food into soluble food substances
Air  Contains O2 required for respiration to produce energy for germination and growth
Suitable
temperature
 Suitable temperatures ensure enough hear to activate enzymes for chemical actions.
 Temperatures that are too high destroy the enzymes.
 Temperatures that are too low inactivate the enzymes
Physical changes of green pea seedling during germination
Set-up of apparatus in determining the conditions required for germination of seeds

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4.12 Vegetative Reproduction in Flowering Plants
 Vegetative reproduction is widely used in agriculture and research. This method produces high
quality young plants very quickly.
 Young tissues from shoot, roots and leaves can be used as vegetative parts in tissue culture 组织培养
techniques.
Vegetative reproduction
 Vegetative reproduction – A method of asexual reproduction carried out by some flowering plants.
 Young plants are produced from a part of parent plant other than flower.
 Young plants and parent plant are genetically alike and have same characteristics.
 These structures have young buds and food stores for growing young plants.
Part of the plant Vegetative organ Examples
Stems
地下茎
Runners are stems
that grow along the
soil surface. Shoots
grow from the
nodes and become
new plants.
Tubers 块茎 and
rhizomes 根茎 are
underground stems
that store food.
Green shoots grow
from their buds to
form new plants.
Bulbs 鳞茎 are
modified stems
wrapped in swollen
leafy bases. Buds
grow in the stem
between leaves.
Green shoots grow
from the buds.
Water lettuce Strawberry
Ginger rhizome
Potato tuber
Hyacinth Onion bulb

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Corms 球茎 are
short, thick and
round underground
stems. New plant
grows from a bud,
using the stored
food in the stem.
Leaves
Leaves of some
plants develop buds
and adventitious
roots along their
margin when
placed in damp
soil.
Roots
Roots of some
plants can store
food. When parent
plants die, roots
grow into new
pants.
Shoots
Suckers are
underground shoots
bearing scale
leaves. They
produce shoots
from their roots.
There shoots
develop into new
plants.
Yam
Byrophyllum leaf
Begonia
Sweet potato
Carrot
Banana

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The application of research on vegetative reproduction in agriculture
 Research on vegetative reproduction is carried out by agencies such as MARDI and MPOB to
produce new varieties of crops, increase yield within short time and improve quality.
 Stem cuttings 切茎法 have been used for very long time to produce new plants.
 One technological development on asexual reproduction is tissue culture that produces many young
plants in short time.
 The young plant produced is called clone 克隆.
Tissue culture