Biology
Scope
The paper typically covers cell structure and organelles, cell division, biomolecules and enzymes, human physiology (digestive, respiratory, circulatory, excretory, nervous and endocrine systems), blood and immunity, genetics, photosynthesis and respiration, basic ecology, classification, and vitamins/mineral deficiencies.
Build the framework first
Know the difference between prokaryotic and eukaryotic cells, and the job of each organelle: mitochondria for aerobic respiration, ribosomes for protein synthesis, chloroplasts for photosynthesis, lysosomes for digestion of waste. Learn mitosis versus meiosis as a contrast - mitosis gives two genetically identical diploid cells; meiosis gives four genetically varied haploid gametes. In physiology, learn each system as a pathway (mouth → oesophagus → stomach → small intestine → large intestine) with one function and one enzyme per stop. For genetics, be fluent with dominant/recessive, genotype versus phenotype, and monohybrid ratios (3:1 phenotype, 1:2:1 genotype).
Traps
Mixing up arteries and veins (arteries carry blood away from the heart, not necessarily oxygenated blood). Forgetting that the pulmonary artery is the exception carrying deoxygenated blood. Confusing the light-dependent and light-independent reactions of photosynthesis. Assuming enzymes are consumed in reactions (they are not). Confusing vitamins with minerals, and forgetting which deficiency causes which disease.
Worked example
A human body cell has 46 chromosomes. After mitosis, each daughter cell has 46 chromosomes and is diploid. After meiosis, each gamete has 23 chromosomes and is haploid. Fertilisation restores 46.
Rule of thumb
When a question asks "which structure performs X", answer with the organelle or organ, not the process - and check whether the question wants the site or the product.