Biology
Cells and molecules
Know prokaryote versus eukaryote: bacteria lack a nucleus and membrane-bound organelles. Match organelles to jobs - mitochondria produce ATP, chloroplasts carry out photosynthesis, ribosomes synthesize protein, the nucleus stores DNA. The four biomolecule classes are carbohydrates (quick energy), lipids (storage and membranes), proteins (structure and enzymes), and nucleic acids (information).
Energy flow
Photosynthesis stores energy; cellular respiration releases it. Only about 10% of energy passes to the next trophic level, so energy pyramids are always upright and top predators are few.
Genetics
Information flows DNA → RNA → protein. Mitosis yields identical diploid cells; meiosis yields four haploid gametes with recombination. In the monohybrid cross Aa × Aa, offspring are 1 AA : 2 Aa : 1 aa - a 3:1 phenotype ratio and a 25% chance of the recessive phenotype.
Human systems
Trace blood: right atrium → right ventricle → lungs → left atrium → left ventricle → body. Arteries carry blood away from the heart, but not always oxygenated blood - the pulmonary artery is deoxygenated.
Ecology and evolution
Distinguish mutualism, commensalism, and parasitism. Natural selection acts on variation that already exists; it does not create variation on demand.
Trap
"Dominant" means expressed when present, not more common in the population.