Living Things and Life Processes
This domain tests whether you can decide what makes something alive, name the seven life processes, and use cells and classification to compare organisms.
The seven life processes
All living things carry out movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Respiration is a chemical reaction in cells that releases energy from food; breathing is only the movement of air in and out of the lungs. Excretion removes waste made by cells, such as carbon dioxide and urea, while egestion is undigested food leaving the gut. Sensitivity means responding to a stimulus such as light, heat or touch.
Cells and classification
Animal cells have a membrane, cytoplasm and nucleus. Plant cells add a cell wall, chloroplasts and a large permanent vacuole. Vertebrates have a backbone and split into fish, amphibians, reptiles, birds and mammals; invertebrates include insects, worms, snails and spiders. A species is a group whose members can breed together to produce fertile young.
Worked example
A pupil says a salt crystal is alive because it grows and 'moves' when pushed. Test each process: it has no cells, no respiration, no nutrition, no excretion and no reproduction, and it grows by adding material to the outside rather than from inside. Conclusion: it is not alive.
Traps that cost marks
Do not use movement alone as evidence of life - plants are rooted but alive. Never write that plants respire only at night; they respire all the time and photosynthesise only in light. Keep excretion separate from egestion. A seed or an egg is dormant, not non-living, because it still carries out life processes slowly.