1. Cells
The cell is the basic unit of life. Plant and animal cells share many parts, but plant cells also have a cell wall, chloroplasts and a large vacuole.
| Part | Function |
|---|---|
| Nucleus | Contains DNA and controls the cell |
| Mitochondria | Release energy through respiration |
| Cell membrane | Controls what enters and leaves |
| Chloroplast (plants) | Carries out photosynthesis |
| Cell wall (plants) | Gives support and shape |
2. DNA and genes
DNA (deoxyribonucleic acid) carries the instructions for building and running an organism. It is shaped like a double helix and built from four bases: A pairs with T, and C pairs with G. A gene is a section of DNA that codes for a protein.
3. Photosynthesis and respiration
Plants make food using light energy:
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Respiration releases energy from glucose in nearly all living cells:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
4. Evolution and natural selection
Individuals in a population differ. Those with traits better suited to their environment are more likely to survive and reproduce, passing those traits on. Over many generations, populations change. This is natural selection, proposed by Charles Darwin.
5. Human body systems
- Circulatory: the heart and blood vessels carry blood around the body.
- Respiratory: the lungs bring in oxygen and remove carbon dioxide.
- Digestive: breaks food down so nutrients can be absorbed.
- Nervous: the brain, spinal cord and nerves send signals.
- Skeletal and muscular: support the body and allow movement.