PSLCE Primary Science cheat sheet

The seven life processes are movement, respiration, sensitivity, growth, reproduction, excretion and nutrition; a thing is living only if it shows all seven.

Respiration releases energy from food inside cells; breathing is only the movement of air in and out of lungs, so plants respire without breathing.

Excretion removes waste made by the organism itself (carbon dioxide, urine, sweat); egestion removes undigested food, which was never absorbed.

Photosynthesis stores energy: carbon dioxide + water + light gives glucose + oxygen; respiration releases it in both plants and animals.

Sensitivity (response to stimuli) requires a receptor, a coordinating link and an effector; plant shoots are positively phototropic and roots positively geotropic.

Growth is a permanent increase in size and cell number; a crystal growing larger is not growth because no cells are produced.

Classification key rule: each question must have exactly two mutually exclusive answers, and each organism must reach one named group.

Root hair cells have a large surface area for absorbing water and mineral salts; root hairs also anchor the plant.

Xylem carries water and dissolved minerals upward only; phloem carries dissolved sugars in both directions.

Leaves are broad and thin with stomata and chlorophyll to maximise light absorption and gas exchange for photosynthesis.

Flower parts: sepals protect the bud, petals attract pollinators, stamens (anther + filament) make pollen, carpel (stigma, style, ovary) receives pollen.

Pollination is pollen transfer; fertilisation is the fusion of male and female gametes inside the ovule, forming a seed and then a fruit from the ovary.

Seeds need water, oxygen and a suitable temperature to germinate; light is not required for germination of most seeds.

Dispersal by wind uses light winged or parachute fruits; by animals uses hooks or edible fruit; by water uses buoyant waterproof coats.

Digestion order: mouth (teeth, saliva/amylase) - oesophagus - stomach (acid, churning) - small intestine (main absorption, villi) - large intestine (water absorption) - rectum.

Bile from the liver, stored in the gall bladder, emulsifies fats; the pancreas releases enzymes into the small intestine.

Breathing mechanics: intercostal muscles and diaphragm contract, rib cage rises and flattens, chest volume increases and pressure falls, air enters.

Blood pathway: right atrium - right ventricle - lungs - left atrium - left ventricle - body; arteries carry blood away from the heart, veins toward it.

A balanced diet needs carbohydrates and fats for energy, proteins for growth and repair, vitamins and minerals for health, fibre for the gut, water for transport.

Deficiency rules: vitamin C lack causes scurvy, vitamin D or calcium lack causes rickets, iron lack causes anaemia, protein-energy lack causes kwashiorkor.

Health protection: vaccination gives immunity before exposure; handwashing, safe water, cooking food well and covering food reduce disease transmission.

Three states: solids keep shape and volume, liquids keep volume but take container shape, gases fill any container; particle spacing and motion explain all three.

Changes of state: melting, freezing, evaporation, condensation, sublimation; these are physical changes because no new substance forms.

Dissolving is not melting: a solute spreads through a solvent and can be recovered by evaporation; solubility rises with temperature for most solids.

Filtration separates an insoluble solid from a liquid; evaporation recovers a dissolved solid; distillation separates a solvent from a solution.

A chemical change produces a new substance, shown by colour change, gas, heat or light, precipitate, or a change not easily reversed.

Density = mass / volume; an object floats in a liquid if its density is lower than the liquid's density.

Thermal conductors (metals) transfer heat quickly; insulators (wood, plastic, air, wool) slow heat transfer; air trapped in wool keeps warmth.

Force is a push or pull measured in newtons (N); forces can change speed, direction or shape; friction opposes motion between surfaces in contact.

Weight = mass x gravitational field strength (about 10 N/kg on Earth); mass in kilograms does not change with location, weight does.

Balanced forces give no change in motion; unbalanced forces cause acceleration or deceleration in the direction of the resultant force.

Air resistance and water resistance increase with speed and surface area; streamlining reduces them; lubrication and smooth surfaces reduce friction.

Energy forms include kinetic, gravitational potential, elastic, chemical, thermal, light and sound; energy is transferred, never created or destroyed.

Levers: a pivot, effort and load; a longer effort arm gives greater turning effect. Gears, pulleys and inclined planes trade force for distance.

Speed = distance / time; average speed uses total distance over total time, so a fast then slow journey uses the whole trip.

Water cycle order: evaporation and transpiration - condensation forming clouds - precipitation - run-off and infiltration into soil and groundwater.

Evaporation is faster with higher temperature, more wind and greater exposed surface area; condensation needs cooling of water vapour.

Weather is day-to-day conditions; climate is the long-term average pattern of a place, so one cold day does not disprove a climate trend.

Air is about 78% nitrogen, 21% oxygen and small amounts of carbon dioxide, water vapour and noble gases.

Renewable resources (sunlight, wind, water, biomass) are replaced naturally; fossil fuels (coal, oil, gas) are non-renewable and release carbon dioxide.

Soil layers: topsoil rich in humus and roots, then subsoil, then weathered rock; soil forms slowly from broken rock plus decayed matter.

The Sun drives weather and the water cycle; the Earth's rotation causes day and night, and its tilted orbit causes the seasons.

Food chain rule: arrows show the direction of energy flow, from producer to consumer; energy is lost as heat at each level, so chains are short.

Producers make their own food by photosynthesis; consumers eat other organisms; decomposers break down dead matter and return nutrients to soil.

A habitat is where an organism lives; a population is one species in an area; a community is all populations together; an ecosystem adds the non-living factors.

Competition and predation control population size; removing a predator can cause prey numbers to rise and then crash through overgrazing.

Pollution effects: excess fertiliser causes algal growth and oxygen loss in water; smoke and sulfur dioxide cause acid rain and breathing problems.

Conservation actions: protected areas, replanting trees, reducing plastic waste, recycling, and using renewable energy reduce habitat damage.

Adaptation examples: thick fur for cold, long roots for dry soil, camouflage for hiding, and streamlined bodies for moving in water.

Fair test: change one independent variable, measure one dependent variable, and keep all other variables constant.

Reliability improves with repeated readings; precision improves with finer-scale instruments; accuracy is closeness to the true value.

Reading rules: read at eye level, note the smallest scale division, and read a thermometer or measuring cylinder at the bottom of the meniscus.

Tables need a heading with unit for every column; graphs need labelled axes with units, a suitable scale and even spacing.

A line graph suits continuous data, a bar chart suits categories, and a scatter or tally suits counting occurrences.

A conclusion must be supported by the data; an anomalous result should be checked and repeated rather than hidden or deleted silently.

A prediction is a testable statement about what will happen; a hypothesis links variables with a reason that can be tested.

Crop yields rise with fertile soil, correct spacing, weeding, pest control and water at the right time; crop rotation reduces soil nutrient loss and pests.

Compost and manure add humus and nutrients; overuse of chemical fertiliser can harm soil and pollute nearby water.

Irrigation methods: drip and sprinkler use less water than flood irrigation; mulching reduces evaporation from the soil surface.

Simple farm machines use levers, pulleys and wheels; a wheelbarrow is a lever with the wheel as pivot and the load between pivot and effort.

Food preservation: drying, salting, pickling, canning, freezing and smoking slow the growth of microorganisms; refrigeration slows but does not stop it.

Safe water treatment order: settlement or filtration to remove solids, then boiling or chlorination to kill pathogens.

Energy-saving choices at home: switch off unused appliances, use insulated cooking pots, and replace incandescent bulbs with efficient ones.