- Petals (attract and serve as landing platform for pollinators)
- Sepals (protect parts of the flower during bud stage)
- Epicalyx (forms a layer outside the sepals)
- Receptacle (enlarged end of stalk that holds other parts of the flower in place)
- Stalk (attaches the flower to the plant)
- Ovary (contains ovules)
- Style (holds stigma in optimal position for pollination)
- Stigma (secretes sugary fluids to stimulate growth of pollen grain, site of pollination)
- Anther (2 lobes that contain pollen sacs that produce pollen grains)
- Filament (contains phloem and xylem to provide nutrients for development of anther)
Self pollination
-Features
- Anthers and stigmas mature at the same time
- Stigma situated beneath the anthers
- Flowers do not bloom
-Advantages
- Only 1 plant required, reducing dependency on pollinators
- Beneficial traits are directly passed onto offsprings
- Probability of self-pollination is higher than cross pollination, thus saving pollen grains and energy in the process
-Disadvantages
- Weaker and smaller offspring that are less resistant to diseases and environmental challenges
Cross pollination
-Features
- Plant bears only male or female flowers
- Anther and stigma situated far away from each other
- Anther and stigma mature at different times
-Advantages
- Offspring inherit beneficial traits from both parents
- More variety of offspring are produced, making the plants more adaptive to environment changes
- Seeds are viable over a ling period of time.
-Disadvantages
- 2 plants required, increasing dependency on pollinators
- Probability of self-pollination is higher than cross pollination, this method of pollination uses more pollen grains and energy in the process
Insect pollinated flower
- Large and brightly coloured petals
- Nectar present with nectar guides on petals
- Usually scented
- Small stigmas and stamen do not stick out of flower
- Large amount of large and rough pollen
Wind pollinated flower
- Absence of petals
- Usually unscented
- Large feathery stigmas and stamen protrude out of flower
- Large amount of lightweight, smooth and small pollen grains
Process of pollination and fertilization
- Pollen settles on mature stigma
- Pollen grain produces a tube that extends to the ovary
- Pollen tube enters the ovules in the ovary
- Male gametes are released and they fused with female gametes
Sexual reproduction in humans
Puberty, the process whereby the child's body matures into an adult body which is capable of reproduction.
Puberty, the process whereby the child's body matures into an adult body which is capable of reproduction.
- Release of hormones form the brain to the sex organs (testes for males and ovaries for females)
- Sex organs start secreting sex hormones (testosterone for males and oestrogen for females)
- Sex organs initiate production of gametes (sperm for male and ovum for female)
- Secondary sexual characteristics also start developing
Male secondary sexual characteristics
- Growth of hair on various parts of the body
- Broadening of chest and shoulders
- Enlargement of penis and testes
- Oil and sweat glands become more active, leading to acne in some cases
- Deepening of voice
- Increase in muscle mass and height
- Confusion,giggly excitement
Female secondary sexual characteristics
- Growth of hair on various parts of the body
- Broadening of hips
- Enlargement of breats
- Oil and sweat glands become more active, leading to acne in some cases
- Confusion,giggly excitement
Male reproductive system and its functions
 |
| Male reproductive system |
- Testes (production of sperms and testosterone)
- Epididymis (temporary storage of sperm and muscles here are used in ejaculation)
- Sperm duct (transport sperm from Epididymis to urethra)
- Glands (production of alkaline seminal fluid which activates and nourishes sperms)
- Penis (insert into vagina when erected)
Physiology of erection and ejaculation
- Arterioles bring blood to penis and its erectile tissues dilate
- Blood fills up blood spaces in erectile tissue
- Penis becomes turgid
- Epididymis contracts
- Semen is released
Female reproductive system and its functions
- Ovary (production of ovum and oestrogen)
- Oviduct (Muscular, strong contractions of cilia to move mature ovum along oviduct)
- Uterus (push foetus out during birth)
- Uterine lining (soft and smooth to prepare for implantation of fertilized egg)
Structural adaptations of a sperm
 |
| Structure of a sperm |
- Acrosome (contains an enzyme called acrosin which digests the ovum's thin cell membrane so that the sperm can fertilize the ovum)
- Nucleus (contains the genes of the male)
- Minimal cytoplasm (reduce resistance of the sperm swimming towards the ovum)
- Middle piece (contains spiral mitochondrion which supplies energy for beating the tail)
- Tail (propel the sperm)
Menstrual cycle
Average period of each menstruation cycle is around 28 days but may vary from 14 to 35 days due to external factors
Menstruation phase (day 1-14)
Average period of each menstruation cycle is around 28 days but may vary from 14 to 35 days due to external factors
Menstruation phase (day 1-14)
- Menstrual bleeding occurs a discharge of menses and blood
- During this period, oestrogen is secreted in increasing concentration
- Menstruation stops at day 7 due to high levels of oestrogen and uterine lining is at its thinnest now
- Beyond day 7 the uterine lining begins thickening again
- A new ovum begins maturing and continues to mature beyond day 7
Ovulation (day 14)
- Oestrogen reaches a maximum
- A sudden surge in luteinizing hormone level triggers release release of mature ovum from ovaries
- Mature ovum may only survive 24 hours or less if not fertilized
- Fertile period of a woman is thus on day 11-16
Luteal phase (day14-28)
- After ovulation, the ovaries start production of progesterone
- This encourages growth of uterine lining and more blood capillaries in the endometrium tissue
- The uterine lining ultimately reaches its thickest and is maintained by high levels of progesterone in preparation of fertilized egg
- If the fertilized egg is not implanted within day 14-28, levels of oestrogen and progesterone will fall sharply, resulting in breakdown of uterine wall.
- Unfertilized egg, endometrial tissues, blood capillaries and blood will be removed through menstrual bleeding, marking a new menstruation cycle
 |
| Growth of a zygote |
- After the zygote is formed, cell division in the zygote occurs to form a ball of undifferentiated cells.
- This ball of cells then form simple tissue layers and is known as an embryo
- Later, the embryo forms distinguishable organs and we term this as the foetus.
- Foetus is then nourished and protected by the following features in the womb:
-Amniotic fluid
- Supports and cushions the foetus in the uterus
- Protects the foetus against physical injury
- Allow the foetus to move freely during gestation
- Acts as a lubricant to reduce friction in the birth canal during birth
-Placenta
- Allows oxygen, nutrients and antibodies to diffuse from mother to foetus
- Produce progesterone
- Allow excretory products to diffuse from foetus to mother
-Umbilical cord
- Umbilical arteries transport deoxygenated blood and metabolic wastes from foetus to placenta
- Umbilical vein transports oxygenated blood, nutrients and other useful anti-bodies from placenta to foetus
Sexually transmitted diseases
- Gonorrhea
- Syphilis
- AIDS
- HIV
- Herpes
- Chlamydia
How to prevent them
- Practice monogamy or abstinence
- Do not abuse drugs
- Do not share instruments that break the skin
- Use birth control
Birth control
- Rhythm method (woman tracks menstrual cycle and doesn't have sex during fertile period)
- Withdrawal method (withdraw penis before ejaculation)
- Spermicide (chemical sprayed in vagina to kill sperms)
- Condom (a rubber sheath is put onto the penis during intercourse)
- Diaphragm cap (a rubber cap cap is fitted onto the cervix)
- 'Pill' (contains female hormones to prevent ovulation)
- Injection ( inject female hormones to prevent ovulation)
- Ligation (oviducts are tied up so sperms do not meet the ovum
- Vasectomy (Sperm ducts are cut and tied to prevent sperms from being released)
Reflections
This term, we were learning about acids and bases as well as plant reproduction. We were also taught how to write chemical equations. In the lessons for acids and bases, I learnt that not all acids are harmful to us and it is actually humankind that produces corrosive acid. There are also various kinds of reactions between acids and other materials as well as various kinds of indicators for finding out the pH of a substance aside from litmus paper. To complete many of our worksheets we had to write chemical equations which was at first quite hard as we had to balance the equation and find out the chemical names of the various elements. It gradually becomes easier if you can memorise all the elements and their charges. In the plant reproduction unit, I felt that it was an extension of what we had learnt in P3 except that we were more in-depth about the various segments of the flower and how reproduction occurs. In this term test I obtained 33/45, which was quite surprising as I am not very good at chemistry.
This term, we were learning about acids and bases as well as plant reproduction. We were also taught how to write chemical equations. In the lessons for acids and bases, I learnt that not all acids are harmful to us and it is actually humankind that produces corrosive acid. There are also various kinds of reactions between acids and other materials as well as various kinds of indicators for finding out the pH of a substance aside from litmus paper. To complete many of our worksheets we had to write chemical equations which was at first quite hard as we had to balance the equation and find out the chemical names of the various elements. It gradually becomes easier if you can memorise all the elements and their charges. In the plant reproduction unit, I felt that it was an extension of what we had learnt in P3 except that we were more in-depth about the various segments of the flower and how reproduction occurs. In this term test I obtained 33/45, which was quite surprising as I am not very good at chemistry.
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