Ch 7 covers evolution — origin of life theories, evidences of evolution (anatomical, embryological, molecular), Darwin's natural selection, Hardy-Weinberg principle, and the timeline of human evolution.
Chemical evolution: Oparin-Haldane hypothesis. Miller-Urey experiment: simulated early atmosphere → amino acids. Evidences: homologous organs (same structure, different function — divergent evolution), analogous organs (different structure, same function — convergent evolution), fossils, embryology (von Baer), molecular (DNA/protein homology).
Darwin: variation + struggle for existence + survival of fittest → natural selection. Types: stabilising (average), directional (one extreme), disruptive (both extremes). Hardy-Weinberg: allele frequencies remain constant if no evolution (p² + 2pq + q² = 1). Five agents of change: mutation, gene flow, drift, non-random mating, selection.
Download: https://ncert.nic.in/textbook/pdf/lebo107.pdf | Complete book: https://ncert.nic.in/textbook/pdf/lebo1ps.zip
It states that allele and genotype frequencies in a population remain constant across generations if: (1) no mutation, (2) no migration (gene flow), (3) random mating, (4) no genetic drift (large population), (5) no natural selection. The equation is p² + 2pq + q² = 1 (where p + q = 1 for two alleles). Any deviation from these conditions leads to evolution — change in allele frequencies.
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