Biology - Science Track
What the paper tests
The biology paper is set in Khmer and covers cell structure and transport, photosynthesis and respiration, genetics, human physiology, and ecology. Expect labelled-diagram recall, short explanations, and simple genetic or experimental reasoning.
Core rules
- Photosynthesis stores energy in glucose; aerobic respiration releases it. Respiration transfers energy to ATP rather than “making energy”.
- In osmosis, water moves from higher water potential (lower solute concentration) to lower water potential.
- Use a Punnett square for crosses; distinguish genotype from phenotype.
- In ecology, energy decreases along a food chain; pyramids of numbers can invert, but pyramids of energy do not.
Worked example
Two heterozygous pea plants (Aa×Aa) are crossed, where A is dominant and a is recessive. The gametes are A and a on both sides. The Punnett square gives AA, Aa, Aa, aa: a 1:2:1 genotype ratio and a 3:1 phenotype ratio. The probability of a recessive phenotype is 1/4, or 25%. The probability of a heterozygous offspring is 1/2.
Traps
Writing “3:1” for genotypes; saying transcription produces protein (translation does); confusing breathing with respiration; and describing a graph without quoting figures.