Combined Science Form 2 Vocabulary Review

BIOLOGY: CELLS AND LEVELS OF ORGANISATION

Introduction to Life Processes

• Organisms are distinguished from non-living things (like iron ore, tables, or cars) by seven basic life processes:     * Nutrition: The need for nutrients.     * Respiration: Getting energy from food.     * Excretion: Removal of waste products.     * Homeostasis: Controlling internal conditions.     * Response: Reacting to environmental changes.     * Reproduction: Producing offspring.     * Growth and Development.

Modern Classification System

• Carolus Linnaeus: An 18th-century Swedish doctor and botanist who pioneered the modern classification system.

• Five Kingdoms:     * Animalia: Multicellular, no cell walls, ingest food, no chlorophyll, mobile (e.g., Hippotragus niger - sable antelope).     * Plantae: Multicellular, photosynthetic, cellulose cell walls, vascular tissue, distinct parts (roots, stems, leaves) (e.g., Chlorophytum comosum).     * Fungi: Absorb food from other organisms or decaying material, chitin cell walls, usually multi-nucleated, no chlorophyll (e.g., Rhizopus stolonifer).     * Protista: Usually single-celled, distinct nucleus (e.g., Amoeba proteus, Plasmodium, algae).     * Monera (Bacteria): Single-celled, no nucleus (e.g., Escherichia coli, blue-green algae).

Taxonomic Hierarchy and Nomenclature

• Levels of Classification: Kingdom → Phylum → Class → Order → Family → Genus → Species.

• Species Definition: A group of organisms with common features that can freely interbreed to produce fertile offspring.

• Binomial System: Two-part scientific name consisting of the Genus (capitalized) and species (lowercase). Both are italicized in print or underlined separately when handwritten (e.g., Homo sapiens, Panthera pardus).

Variation within Species

• Phenotype: Observable characteristics in a population.

• Genotype: The genetic make-up of an individual.

• Types of Variation:     * Continuous Variation: Characteristics that change gradually over a range (e.g., height, weight, foot length). Data is represented using a histogram.     * Discontinuous Variation: Limited number of distinct possibilities (e.g., blood groups A, B, AB, O; gender; tongue rolling; attached earlobes). Data is represented using a bar graph.

• Causes of Variation: Genetic inheritance, environment (e.g., soil acidity affecting hydrangea color), age, injury, disease, and mutation (change in genetic material during cell division).

Evolution and Selection

• Charles Darwin and Alfred Wallace: Proposed the theory of evolution via Natural Selection.

• Natural Selection Principles:     * Variations suited to the environment increase survival.     * Successful individuals reproduce, passing on favorable traits.     * Populations become more adapted over time.

• Artificial Selection: Humans selecting specific traits for breeding.     * Example: Wild mustard (Brassica) modified into kohlrabi (stem), kale (leaves), broccoli (flower buds/stems), Brussels sprouts (lateral leaf buds), cabbage (terminal leaf buds), and cauliflower.     * Example: Mashona cattle in Zimbabwe selected for hardiness and docility.

• Genetic Engineering: Introducing specific genes into organisms to create useful traits (e.g., pest-resistant cotton or bananas).

BIOLOGY: NUTRITION

Plant Nutrition and Photosynthesis

• Autotrophs (Producers): Organisms like green plants that make their own food from inorganic nutrients ($CO_2$, water, minerals).

• Photosynthesis Process: Converts light energy into chemical energy (glucose/starch).

• Word Equation:     * $\text{carbon dioxide} + \text{water} \xrightarrow[\text{chlorophyll}]{\text{light energy}} \text{glucose} + \text{oxygen}$

• Leaf Adaptations:     * Broad blade for surface area.     * Waxy transparent cuticle for protection.     * Stomata for gas exchange.     * Mesophyll tissue containing chloroplasts with chlorophyll.     * Vascular Bundles: Xylem (transports water) and Phloem (transports manufactured food/translocation).

Trophic Levels and Interdependence

• Heterotrophs (Consumers): Depend on producers for food.     * Herbivores: Feed only on plants (e.g., grazers like cattle, browsers like giraffes).     * Carnivores: Eat meat (e.g., predators like lions, scavengers like vultures).     * Omnivores: Eat both plants and animals (e.g., humans, dogs).     * Detritivores/Decomposers: Feed on organic waste/dead matter (e.g., earthworms, bacteria, fungi).

• Food Chains and Webs: Arrows indicate the flow of energy. Energy is lost at each level (for respiration, growth, movement).

• Ecological Pyramids: Show biomass, energy, or numbers at different feeding levels.

Human Nutrition and Digestion

• Five Stages of Nutrition:     1. Ingestion: Food enters the mouth.     2. Digestion: Mechanical (teeth) and chemical (enzymes) breakdown.     3. Absorption: Nutrients move into the blood.     4. Assimilation: Nutrients incorporated into cell structures.     5. Egestion: Removal of undigested waste (faeces) via the anus.

• Digestive Tract (Alimentary Canal): Mouth → Oesophagus (moves food by peristalsis) → Stomach (contains gastric juice and $HCl$; produces chyme) → Small Intestine (main site of chemical digestion and absorption; uses villi and microvilli) → Large Intestine (absorbs water; includes the colon) → Rectum → Anus.

• Accessory Organs: Teeth, tongue, salivary glands, pancreas, liver, gallbladder.

BIOLOGY: RESPIRATORY SYSTEMS

Cellular Respiration

• The process of releasing energy from nutrients for cellular activity.

• Word Equation:     * $\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}$

• Chemical Cycling: Photosynthesis and respiration are linked; the products of one are the reactants of the other.

Human Respiratory Anatomy

• Air Passages: Nasal cavities (filter dust via cilia and mucus) → Pharynx → Glottis (covered by epiglottis) → Larynx (voice box) → Trachea (held open by C-shaped cartilage rings) → Bronchi → Bronchioli → Alveoli.

• Gaseous Exchange: Occurs in the alveoli, which are surrounded by capillary networks. Surfaces are thin and large in area.

• Breathing Mechanism:     * Inhalation (Active): Diaphragm contracts/moves down, ribcage moves up/out, lung volume increases, pressure decreases, air rushes in.     * Exhalation (Passive): Muscles relax, volume decreases, pressure increases, air is pushed out.

• Control Centre: Located at the base of the brain; controls involuntary breathing rate and coordinates it with heart rate.

BIOLOGY: TRANSPORT SYSTEMS

Physical Processes of Transport

• Diffusion: Net movement of molecules from high to low concentration until dynamic equilibrium is reached.

• Osmosis: Special diffusion of water through a selectively permeable membrane (e.g., water moving from soil into roots).

• Active Transport: Movement of molecules against a concentration gradient using energy and transport proteins.

Vascular Systems in Plants

• Xylem: Dead cells (vessels/tracheids) thickened with lignin; transports water and minerals upwards.

• Phloem: Living cells (sieve tubes and companion cells) that transport sugars via translocation.

• Internal Anatomy (Dicotyledonous):     * Root: Central vascular cylinder (xylem in a cross-shape), endodermis, cortex, epidermis with root hairs.     * Stem: Vascular bundles arranged in a ring; xylem on inside, phloem on outside, separated by cambium; pith in center.

Human Circulatory System

• The Heart: A four-chambered muscular pump.     * Atria (Upper): Receive blood (Right: deoxygenated from body; Left: oxygenated from lungs).     * Ventricles (Lower): Pump blood (Right: to lungs; Left: thick-walled, to entire body).     * Valves: Tricuspid (right side), Bicuspid/Mitral (left side), and Semilunar (at exits to arteries).

• Blood Vessels:     * Arteries: Thick elastic walls, high pressure, carry blood away from heart.     * Capillaries: Microscopic, one-cell thick for exchange of gases and nutrients; produce tissue fluid.     * Veins: Thin walls, carry blood to heart, contain valves to prevent backflow.

• Blood Composition:     * Plasma (55%): Liquid containing water, salts, nutrients, and hormones.     * Red Blood Cells (Erythrocytes): Biconcave shape, no nucleus, contain haemoglobin for $O_2$ transport.     * White Blood Cells (Leucocytes): Immune defense; can pass through capillary walls.     * Platelets: Involved in blood clotting.

BIOLOGY: REPRODUCTIVE SYSTEMS

Plant Reproduction

• Double Fertilisation: Unique to flowering plants.     * One male gamete + Egg cell → Embryo (consists of radicle/root and plumule/shoot).     * One male gamete + Two central cells → Endosperm (food store).

• Seed Types:     * Monocotyledonous: One seed leaf (cotyledon); separate endosperm (e.g., mealie/maize grain). Protected by coleoptile (shoot sheath) and coleorhiza (root sheath).     * Dicotyledonous: Two cotyledons; endosperm absorbed into cotyledons (e.g., bean seed).

Human Reproductive Anatomy

• Male System: Testes (produce sperm/testosterone), scrotum (temperature control), epididymis, sperm ducts, prostate/seminal glands (produce semen), and penis.

• Female System: Ovaries (produce eggs/oestrogen/progesterone), Fallopian tubes (site of fertilisation), Uterus (site of implantation), cervix, and vagina (birth canal).

Pregnancy and Birth

• Gestational Timeline: Nine months ($\approx 280 \text{ days}$).

• Placenta: Formed from mother and embryo tissue; allows exchange of nutrients, gases, and waste via the umbilical cord without mixing blood.

• Amnion: Membrane filled with amniotic fluid to cushion the foetus.

• Labour Stages: (1) Cervix widens and amnion breaks; (2) Baby is born; (3) Placenta is expelled.

BIOLOGY: HEALTH AND DISEASE

Categories of Disease

• Infectious (Communicable): Caused by pathogens (viruses, bacteria, fungi, protozoans, parasites).

• Non-Infectious: Caused by lifestyle (social diseases), diet (deficiency), genetics (congenital), or aging (degenerative).

• Infectious Disease Cycle: Pathogen → Reservoir → Portal of Exit → Mode of Transmission → Portal of Entry → Susceptible Host.

Bilharzia (Schistosomiasis)

• Cause: Parasitic flatworms (Schistosoma mansoni or Schistosoma haematobium).

• Hosts: Humans (primary); freshwater snails (secondary).

• Transmission: Larvae penetrate skin in contaminated water.

• Symptoms: Blood in urine (urogenital) or stool (intestinal), organ damage (liver, spleen).

• Treatment: Praziquantel.

CHEMISTRY: SEPARATION OF MIXTURES

Common Methods

• Filtration: Separates insoluble solids from liquids.

• Evaporation: Recovers a solute from a solvent.

• Magnetism: Separates magnetic materials (iron/steel) from non-magnetic ones.

• Decanting: Pouring off less dense liquid from a mixture of immiscible liquids.

• Winnowing: Using wind to separate light chaff from heavy grain.

Industrial Applications

• Water Treatment: Screening → Sedimentation (Flocculant added to clump particles) → Sand/Charcoal Filtration → Chlorination (kills microbes).

• Sugar Processing: Cane is shredded/crushed → Juice extracted → Bagasse (waste fibers) filtered out → Evaporators produce syrup/solid sugar → Molasses remains as byproduct.

CHEMISTRY: MATTER AND SOLUTIONS

Solution Concentration

• Units: Mass per volume ($g/cm^3$) or percentage.

• Liquid Solute Percentage Formula:     * $\frac{\text{volume of solute}}{\text{total volume of solution}} \times 100\%$

The Mole Concept

• Mole: A measure of the number of particles.

• Avogadro’s Constant: $6.023 \times 10^{23}$ particles per mole.

• Colorimetry: Using a colorimeter to measure concentration by light absorption.

CHEMISTRY: ACIDS AND BASES

Neutralisation Reactions

• General Formula: $\text{acid} + \text{base} \rightarrow \text{salt} + \text{water}$

• Specific Salts:     * Hydrochloric acid → Chlorides     * Sulfuric acid → Sulfates     * Nitric acid → Nitrates

• Acid + Carbonates: $\text{acid} + \text{carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}$

Household Applications

• Antacids: Neutralise stomach acid ($HCl$).

• Baking soda ($NaHCO_3$): Releases $CO_2$ to make dough rise.

• Insect Stings: Neutralise bee stings (acidic) with base; wasp stings (alkaline) with weak acid (vinegar).

• Agricultural Lime: Increases soil pH for crops.

CHEMISTRY: INDUSTRIAL SOAP PRODUCTION

Saponification

• Word Equation: $\text{fat/oil} + \text{alkali} \rightarrow \text{soap} + \text{glycerol}$

• Alkalis Used: Sodium hydroxide ($NaOH$) for hard/soft soaps; potassium hydroxide ($KOH$) for liquid soaps.

• Cleaning Mechanism: Soap molecules have a hydrophilic head (water-loving) and a hydrophobic tail (water-hating/oil-loving).

Manufacturing Processes

• Batch Process (Small Scale): Boiling → Separation (adding salt) → Refinement → Pitching (boiling with water to purify).

• Continuous Process (Large Scale): Uses a hydroliser for constant splitting of fats into glycerol and fatty acids.

CHEMISTRY: OXIDATION, REDUCTION, AND COMBUSTION

Redox Reactions

• Oxidation: Gain of oxygen.

• Reduction: Loss of oxygen from a reactant.

• Chemical vs. Physical Changes: Physical changes are reversible and form no new substances (e.g., melting ice). Chemical changes are irreversible and form new products (e.g., rusting iron, burning magnesium).

Combustion of Fuels

• Complete Combustion: Plenty of $O_2$; produces $CO_2 + H_2O + \text{Energy}$.

• Incomplete Combustion: Insufficient $O_2$; produces carbon monoxide (CO), soot (carbon), and less energy.

• Environmental Hazards:     * Acid Rain: From sulfur dioxide ($SO_2$) and nitrogen oxides ($NO_x$).     * Global Warming: From high $CO_2$ levels.     * Deforestation: Uncontrolled tree cutting leading to siltation/erosion.

PHYSICS: MEASUREMENTS AND DATA

SI Units and Density

• Length: Metre ($m$); Mass: Kilogram ($kg$); Time: Second ($s$); Volume: Cubic metre ($m^3$).

• Density Formula:     * $\text{Density} = \frac{\text{mass}}{\text{volume}}$

• Measuring Irregular Objects: Use the displacement method in a measuring cylinder.

Forces and Moments

• Resultant Force: The single net force acting on an object.

• Moment of Force: The turning effect around a fulcrum (pivot).     * $\text{Moment} = \text{force} \times \text{perpendicular distance}$     * Unit: Newton metre ($Nm$).

• Friction: Opposes motion between surfaces. Types include static (before motion) and kinetic (during motion). Reduced by lubricants or ball bearings.

Simple Machines

• Levers:     * 1st Class: Fulcrum between load and effort (e.g., scissors).     * 2nd Class: Load between fulcrum and effort (e.g., wheelbarrow).     * 3rd Class: Effort between fulcrum and load (e.g., fishing rod).

• Other Simple Machines: Inclined plane (ramp), Screw, Pulley, Wedge, Wheel and Axle.

Energy and Waves

• Work Done: $\text{Work} = \text{force} \times \text{distance}$ (measured in Joules, J).

• Potential Energy ($GPE$): $\text{weight} \times \text{height}$.

• Light: Travels in straight lines; forms umbra (complete shadow) and penumbra (partial shadow).

• Sound: Longitudinal wave produced by vibrations; requires a material medium (cannot travel through a vacuum); consists of compressions and rarefactions.

PHYSICS: MAGNETISM AND ELECTRICITY

Magnets

• Ferromagnetic Materials: Iron, Nickel, Cobalt.

• Laws of Magnetism: Like poles repel; unlike poles attract.

• Magnetic Fields: Lines of force move from North to South. Concentrated at the poles.

Electricity

• Current (I): Flow of charge; measured in Amperes (A) with an ammeter.

• Voltage/Potential Difference (V): Measured in Volts (V) with a voltmeter.

• Electrical Power (P): Measured in Watts (W).     * $\text{Power} = \text{Voltage} \times \text{Current}$