General Science
Core toolkit
Biology: the cell as the unit of life (nucleus, cytoplasm, cell membrane, mitochondria, and chloroplasts in plant cells only), plant versus animal cells, the main human systems (digestive, respiratory, circulatory, nervous, excretory), components of blood, vitamins and their deficiency diseases, photosynthesis and respiration, and simple food chains. Chemistry: states of matter and changes of state, atoms, molecules, elements, compounds and mixtures, common symbols and formulae (H₂O, CO₂, NaCl), acids, bases, indicators and pH, and water purification. Earth and space: layers of the Earth, composition of air, the planets in order from the Sun, and rotation versus revolution.
Traps
- Arteries carry blood away from the heart and veins return it. Most arteries carry oxygenated blood; the pulmonary artery is the exception.
- Mixture vs compound: a compound has a fixed ratio and can only be separated chemically.
- Photosynthesis and respiration are near-opposites: the first stores energy and releases oxygen, the second releases energy and carbon dioxide.
- Deficiency pairings are easy to invert; learn each pair in both directions.
- Instrument names: barometer for pressure, hygrometer for humidity, ammeter for current, thermometer for temperature.
Rule of thumb
Whenever a process is named, ask three questions: what goes in, what comes out, and what happens to energy. That single habit settles most biology and chemistry items.
Worked example: photosynthesis is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, requiring sunlight and chlorophyll. Inputs: carbon dioxide and water. Outputs: glucose and oxygen.