Life Sciences
Life Sciences
This domain tests living things and their environments: characteristics and classification, plant and human processes, health, and energy flow through ecosystems. Questions ask you to identify structures, sequence processes, and predict what happens when one part of a living system changes.
Living things and classification
- Living things move, respire, respond to stimuli, grow, reproduce, excrete and need nutrition. Viruses are not usually treated as living cells because they cannot reproduce on their own.
- Vertebrates have a backbone; invertebrates do not. Plants are flowering or non-flowering (ferns, mosses, conifers).
- Cells are the basic unit of life. Plant cells have a cell wall and chloroplasts; animal cells do not.
Plants
- Photosynthesis: carbon dioxide + water, using light and chlorophyll, gives glucose + oxygen. Leaves are broad and thin to absorb light and allow gases to diffuse.
- Roots absorb water and minerals; stems support and transport; transpiration pulls water upward. Pollination transfers pollen, fertilisation forms seeds, dispersal reduces competition, and germination needs water, warmth and oxygen.
- Plants respire day and night; they photosynthesise only in light.
Human body and health
- Digestion breaks food into nutrients absorbed mainly in the small intestine; the large intestine absorbs water. The circulatory system carries oxygen and nutrients, the respiratory system exchanges gases in the lungs, and the skeleton supports, protects and works with muscles.
- A balanced diet needs carbohydrates, proteins, fats, vitamins, minerals, fibre and water. Hygiene and vaccination reduce the spread of disease.
Ecosystems
- Producers make food, consumers eat, and decomposers break down dead material and return nutrients to the soil. Arrows in a food chain show the direction of energy flow. Energy is lost at each level, so chains are short.
- Adaptations help survival; habitat loss and pollution reduce biodiversity.
Worked example
In the food chain grass → grasshopper → frog → snake, frogs are removed by disease. Predict two changes.
Reasoning: grasshoppers lose a predator, so their numbers rise. More grasshoppers eat more grass, so grass cover falls. Snakes lose a food source, so their numbers fall. Each change follows from the feeding relationship, not from a guess.
Traps that cost marks
- Saying plants do not respire, or that they only take in carbon dioxide.
- Drawing food-chain arrows toward the eater instead of in the direction of energy flow.
- Treating decomposers as consumers.
- Thinking energy is recycled rather than lost as heat.
- Confusing pollination with fertilisation.