Life Science
Cells and molecules
Understand the cell as the basic unit of life; compare prokaryotes (no membrane-bound nucleus) with eukaryotes, and plant with animal cells (cell wall, chloroplasts, large central vacuole). Know the four macromolecules: carbohydrates (quick energy), lipids (membranes, long-term storage), proteins (enzymes, structure), and nucleic acids (information). Enzymes are catalysts whose activity depends on temperature and pH. Photosynthesis stores energy in glucose; cellular respiration releases it, and the two are complementary.
Genetics and evolution
DNA → RNA → protein is the central dogma. In Mendelian genetics, distinguish genotype (alleles present) from phenotype (observable trait), and homozygous from heterozygous. Natural selection acts on variation already present in a population; individuals do not "adapt" on demand, and acquired traits are not inherited. Meiosis produces varied gametes and halves chromosome number; mitosis produces identical body cells. Do not confuse the two.
Ecology
Trace energy flow: sunlight → producers → consumers → decomposers, with roughly 10% transferred between trophic levels. Matter cycles (carbon, nitrogen, water); energy does not. Population growth, carrying capacity, symbiosis, and human impacts are frequent contexts.
Worked example
Cross two heterozygous pea plants (Tt × Tt). The Punnett square gives TT, Tt, Tt, tt - a 3:1 phenotypic ratio of dominant to recessive and a 1:2:1 genotypic ratio. If phenotypes are given and genotypes are asked for, work backward from the recessive trait, which must be homozygous.
Traps
An observed correlation is not causation, and "survival of the fittest" means reproductive success, not strength.