Chapter Summary
Evolution explains the origin of life and diversification of organisms through mechanisms such as mutation, recombination, gene flow, genetic drift and natural selection. Evidence includes fossils, comparative anatomy (homology/analogy), biogeography, embryology and molecular data. Concepts cover Hardy–Weinberg equilibrium, adaptive radiation, convergent/divergent evolution, industrial melanism, antibiotic resistance, speciation, isolation barriers, punctuated equilibrium, and human evolution. Origin-of-life models include Oparin–Haldane hypothesis and Miller–Urey experiment.
Evidence
Natural Selection
Genetic Drift
Hardy–Weinberg
Speciation
Human Evolution
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50 Questions & Answers
1) Define evolution.
Heritable change in populations over generations leading to adaptation and new species.
2) State Oparin–Haldane hypothesis.
Life originated abiogenically in a primitive reducing atmosphere, forming organic molecules that assembled into protobionts.
3) What did Miller–Urey demonstrate?
Electric discharges in a reducing gas mixture produced amino acids, supporting chemical evolution.
4) What is the RNA world hypothesis?
Early life used RNA as both genetic material and catalyst before DNA/proteins evolved.
5) Define protobionts/coacervates.
Precellular aggregates of organic molecules with primitive membrane-like boundaries capable of growth/division-like behavior.
6) What is panspermia?
Hypothesis that life or its spores arrived on Earth from space.
7) Name the eras of geological time relevant to life.
Paleozoic, Mesozoic, Cenozoic; Precambrian precedes Paleozoic.
8) What is a fossil?
Preserved remains, impressions, or traces of past life found in rocks or amber.
9) Distinguish homologous and analogous organs.
Homologous: same origin, different functions (divergent evolution). Analogous: different origin, similar function (convergent evolution).
10) Give an example of adaptive radiation.
Darwin’s finches on Galápagos evolving diverse beaks from a common ancestor.
11) Define vestigial organs.
Structures reduced or functionless relative to ancestors (e.g., human appendix, coccyx).
12) What is biogeographical evidence?
Distribution patterns of species across continents support common ancestry and continental drift.
13) How does comparative embryology support evolution?
Early embryos of related species share features indicating common ancestry.
14) What is the molecular clock?
Rate of accumulation of neutral mutations used to estimate divergence times.
15) Define convergent vs divergent evolution.
Convergent: unrelated lineages evolve similar adaptations. Divergent: closely related lineages evolve different traits.
16) What is coevolution?
Reciprocal evolutionary change between interacting species (e.g., pollinators and flowers).
17) What is industrial melanism?
Increase of dark morphs (e.g., peppered moth) due to selection in polluted environments.
18) Give an example of rapid evolution in microbes.
Antibiotic resistance evolving in bacteria under drug selection pressure.
19) State Hardy–Weinberg principle.
Allele/genotype frequencies remain constant under no mutation, migration, selection, drift and random mating.
20) Write H–W equations.
For alleles A (p) and a (q): p + q = 1; genotype frequencies p² (AA) + 2pq (Aa) + q² (aa) = 1.
21) Calculate heterozygote frequency if p = 0.7.
q = 0.3; 2pq = 2 × 0.7 × 0.3 = 0.42 (42%).
22) What is genetic drift?
Random fluctuation of allele frequencies, strongest in small populations; can lead to fixation or loss.
23) Define bottleneck effect.
Sharp reduction in population size causes loss of genetic variation and drift.
24) Define founder effect.
New population founded by few individuals shows allele frequencies different from source population.
25) What is gene flow (migration)?
Movement of alleles between populations via migrants; tends to reduce differences.
26) Types of natural selection?
Directional (shifts mean), Stabilizing (reduces variance), Disruptive (favors extremes → bimodality).
27) Define fitness.
Relative reproductive success of a genotype/phenotype in a given environment.
28) What is sexual selection?
Selection arising from mating success differences (e.g., ornate male traits, female choice).
29) What is balanced polymorphism?
Maintenance of multiple alleles due to heterozygote advantage or frequency-dependent selection (e.g., sickle-cell vs malaria).
30) Distinguish microevolution and macroevolution.
Micro: changes in allele frequencies; Macro: large-scale patterns like speciation and higher-level trends.
31) What is punctuated equilibrium?
Long periods of stasis interrupted by geologically rapid bursts of change.
32) Define cline and ecotype.
Cline: gradual change in trait across geography; Ecotype: locally adapted population.
33) What is species (biological concept)?
Groups of actually/potentially interbreeding natural populations reproductively isolated from others.
34) Allopatric vs sympatric speciation.
Allopatric: geographic isolation; Sympatric: reproductive isolation within same area (e.g., polyploidy in plants).
35) Prezygotic isolation barriers.
Temporal, ecological, behavioral, mechanical, and gametic isolation.
36) Postzygotic isolation barriers.
Hybrid inviability, sterility, and breakdown.
37) Role of polyploidy in speciation.
Chromosome doubling (auto-/allo‑polyploidy) can instantly create reproductive isolation, common in plants.
38) What is adaptive radiation?
Rapid speciation into diverse niches from a common ancestor (e.g., cichlid fishes).
39) What is reinforcement?
Selection for increased prezygotic isolation to avoid maladaptive hybridization.
40) What is hybrid zone?
Region where genetically distinct populations meet and produce hybrid offspring.
41) Outline human evolutionary lineage (simplified).
From early hominins (Australopithecus) → Homo habilis → H. erectus → archaic Homo → H. sapiens (modern humans).
42) Key features of Australopithecus.
Bipedal, small brain (~400–500 cc), lived in Africa ~4–2 mya.
43) Who was Homo habilis?
“Handy man” (~2.4–1.4 mya), larger brain (~600–700 cc), made simple stone tools.
44) Features of Homo erectus.
~1.9 mya–100 kya; brain ~900 cc; controlled fire; broader geographic range (Africa, Asia).
45) Distinguish archaic humans and modern H. sapiens.
Archaic: robust, large brow ridges; Modern: high forehead, chin, brain ~1350 cc, advanced culture.
46) What is Out-of-Africa model?
Modern H. sapiens evolved in Africa and dispersed replacing/admixing with other hominins.
47) Evidence supporting human evolution.
Fossil record, comparative anatomy, archaeological tools, genetic/molecular data (mtDNA, Y‑chromosome).
48) What is cultural evolution?
Non-genetic transmission of knowledge/behavior accelerating human adaptation (language, technology).
49) How do radioactive and relative dating differ?
Radioactive dating uses isotopic decay to estimate absolute age; relative dating orders fossils via stratigraphy.
50) Why is evolution considered a fact and a theory?
Fact: observed change and common ancestry evidence; Theory: well-substantiated explanatory framework (mechanisms and patterns).