Biology
What this domain tests
Biology is the largest science component of the IMAT. It rewards precise school-level knowledge of cell structure, biomolecules, enzymes, metabolism, genetics, molecular biology, evolution, human physiology, reproduction, and ecology. Questions often require applying a definition to a new example rather than recalling a label.
Core rules
- Prokaryotes lack a nucleus and membrane-bound organelles; ribosomes are not membrane-bound and occur in both.
- Enzymes lower activation energy, are not consumed, and have an optimum pH and temperature; denaturation changes shape and function.
- DNA replication is semi-conservative; transcription makes RNA; translation at ribosomes uses mRNA codons and tRNA anticodons.
- In meiosis, homologous chromosomes separate in meiosis I, sister chromatids in meiosis II; crossing over occurs in prophase I.
- Dominant does not mean “more common”; it means expressed in the heterozygote.
- Negative feedback opposes a change and stabilises internal conditions.
Worked example
Two heterozygous parents (Aa × Aa) have a child. What is the probability that two successive children both show the recessive phenotype? A Punnett square gives offspring genotypes 1 AA : 2 Aa : 1 aa, so the probability of the recessive phenotype in one child is 1/4. Independent events multiply: (1/4) × (1/4) = 1/16. The trap is to add 1/4 + 1/4 or to assume the first child’s genotype changes the second.
Traps that cost marks
Do not confuse mitosis with meiosis, or genotype with phenotype. Check whether a question asks for a DNA base sequence, an mRNA codon, or a tRNA anticodon. In physiology, track the direction of a gradient and the hormone that opposes it. In ecology, distinguish population from community and food chain from food web.