Ecosystem
- It is a habitat which has the community of organisms living in it.
- Population is the same kind of organisms living in a particular habitat.
- Community is the different populations living in a particular habitat.
Biotic environment
- It is the interaction between organisms of either the same species or different species mainly for food and shelter.
- The interaction can be classified in terms of:
- predator-prey: one species feeds on another species.
- commensalism: one species gains benefits from another species without causing any harm.
- parasitism: one species gains benefits from another species with harm
- mutualism: two different species are benefited from each other
Abiotic environment
- The abiotic environment are light, water availability, oxygen, humidity, pH level and others.
Nitrogen cycle
- Nitrogen is removed form the air by nitrogen-fixing bacteria and lightning.
- Nitrogen is returned to the air by denitrifying bacteria.
Conservation of ecosystems
- Destructive activities such as over-hunting and deforestation disrupt the delicate balance of ecosystems.
Birth Control
- Birth control is the prevention of the fusion of a sperm and an egg.
- There are temporary birth control methods and permanent birth control methods.
Temporary birth control
- Condom for male: prevents the deposit of sperms in the vagina
- Condom for female: prevents sperms from entering the vagina
- The pill: contains hormones to stop ovulation
- Cap and diaphragm: stops sperms from entering the uterus
- Spermicides: contains chemical substances that kill sperms
- Intra-uterine device (IUD): prevents implantation of embryo
Permanent birth control
- Vasectomy: The vas deferens (sperm duct) is cut and tied to prevent the transportation of sperms from the testis to the penis.
- Ligation: The fallopian tubes are but and tied to prevent the sperms from fusing with the eggs.
Sexually transmitted diseases
- It is the transmission of diseases through exchange of body fluids during sexual activity.
- The diseases are gonorrhoea, syphilis and AIDS.
Gonorrhoea
- It is caused by bacteria through unprotected sex.
- It can be treated by antibiotics at the early stages of infection.
- The symptoms include:
- painful sensation during urination
- infertility
- blindness in baby
Syphilis
- It is caused by bacteria.
- The symptoms include:
- painless sores
- non-itchy rashes
- insanity
AIDS
- It is caused by a virus called HIV.
- AIDS is the serious stage of HIV infections.
- The symptoms of HIV infection include:
- loss of appetite
- prolonged fever
- night sweat
Prevention of sexually transmitted diseases
- The prevention include:
- be faithful to one sex partner
- have protected sex
Sexual reproduction
- It is a reproduction which involves male and female sex cells.
Male reproductive system
- The male sex cells are called sperms.
- Parts: Penis - transfer sperms to the vagina
- allows urine to leave the body
Testis - produces sperms and male sec hormones
Urethra - transport sperms, semen and urine to outside of the penis
Scrotum - holds the testis outside the body
Vas deferens - transport sperms to the penis
Seminal vesicles - produces fluids that mix with sperms to form semen
Epididymis - stores sperms
Female reproductive system
- The female sex cells are called eggs (or ova).
- Ovary - produces eggs and female sex hormones
- Vagina - allows sperms to deposit
- Parts: Uterus - allows the implantation of embryo to occur and nourishes the growth of the foetus
Fallopian tube - transport eggs from the ovaries to the uterus
- allows fertilization to take place
Vagina - allows sperms to deposit
Ovary - produces eggs and female sec hormones
Fertilization
- Fertilization is the fusion of the nucleus of a sperm and the nucleus of an egg to form a fertilized egg called zygote.
- The fertilized egg contains 23 pairs of chromosomes.
- As the zygote contains both parents' chromosomes, the child will inherit certain characteristics from both parents. It is called heredity.
- The zygote develops into a ball of cells called embryo. The embryo implants into the uterus wall. The process is known as implantation.
- The function of the placenta: - provides food, oxygen and water from the mother's blood to the baby's
blood
- removes waster products such as carbon dioxide from the baby's
blood
Menstruation
- Ovulation and menstruation are parts of the menstrual cycle.
- A menstrual cycle has an average of 28 days.
Diffusion
- Diffusion is a process whereby a substance moves from its region of high concentration to its region of low concentration.
- The process is a passive transport which does not require energy to take place.
Diffusion in living organisms
- Organs have specialized features to increase the surface area for diffusion of materials.
Osmosis
- Osmosis is a process whereby water molecules move from the region of high water concentration (high water potential) to the region of low water concentration (low water potential) through a partially (or semi- or selectively) permeable membrane.
- Partially permeable membrane is a membrane that only allows certain substances to pass through.
- All cell membranes of living organisms are partially permeable membranes.
Active transport
- Active transport is a process whereby substances move from their region of low concentration to their region of high concentration.
- Energy is needed for this process to occur.
Cells
- Cells are the building blocks of all living things.
- Living things can be classified into unicellular organisms (one cell only) or multicellular organisms (many cells).
Animals cells
- Animals cells have no cell walls.
- The structure and its function of a cell:
-Cell membrane: control the movement of substances in and out of a cell
-Nucleus: controls the activities of a cell and stores hereditary materials called chromosomes
-Vacuole: stores food and nutrients
-Cytoplasm: allows chemical reactions to take place
Plant cells
- Plant cells have cell walls.
- The structure and its function of a cell:
-Cell membrane: control the movement of substances in and out of a cell
-Nucleus: controls the activities of a cell and stores hereditary materials called chromosomes
-Vacuole: stores food and nutrients
-Cytoplasm: allows chemical reactions to take place
-Chloroplast: contains chlorophyll to absorb sunlight for photosynthesis
-Cell Wall: supports and maintains the shape of the cell
Division of Labour
- Division of labour in living organisms allows more efficient and smooth functioning in the multicellular organisms.
- When a group of cell perform the similar function, they are known as tissue.
- When a group of tissues perform the similar function, they are known as organ.
- When a group of organs perform the similar function, they are known as organ system.
- Various organ systems make up an organism.
- The characteristics of an acid:
- Sour taste
- Able to conduct electricity
- Turns blue litmus paper red
- Reacts with metals, carbonate or alkalis
- The common acids used in the school laboratory are sulfuric acid (H2SO4), nitric acid (HNO3) and hydrochloric acid (HCl).
- The characteristics of an alkali:
- Bitter taste
- Soapy feeling
- Turns red litmus paper blue
- Corrosive
- Universal indicator is used to test the acidity or alkalinity of a solution by showing different colour corresponding to different pH values.
- It is red in strong acids, pale green in neutral and blue or violet in strong alkalis.
- The process of grouping and sorting out is called classification.
- Grouping of object in a proper way always help us to do our work efficiently.
- Classification can be based on similarities and differences.
- Materials which are non-living things are mainly two types.
- Naturally occurring. - Man-made
- Materials can be classified as metals, glass, ceramics, plastics and fiber.
Metals: An element which is shiny, a good conductor of heat and electricity, ductile, malleable, has a high melting point (eg. silver, gold)
Glass: Sand (silica), soda (sodium carbonate) and lime (calcium carbonate) are mixed and melted. Glass is fragile and transparent.
Ceramics: Greek word, 'Keramos' - which means potter's clay - All ceramics are made from various clay. Ceramics are compounds of silicon, carbon, oxygen and nitrogen combined with other elements like sodium, potassium, calcium and boron.
Plastics: Plastics do not occur naturally but are man-made. 'Plastikos' - a greek word meaning 'to mould'. Common types of plastics are polythene, polystyrene, PVC and nylon. Plastics have many uses.
Fiber: Fibers can be both man made like polyester, nylon or natural like cotton or wool.
