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Must-know facts
20 facts
- 1The universe is almost 13.8 billion years old; the earth formed about 4.5 billion years ago; life appeared about 4 billion years ago.
- 2Louis Pasteur disproved spontaneous generation with killed yeast in pre-sterilised flasks: life comes only from pre-existing life.
- 3Oparin and Haldane: life came from non-living organic molecules, preceded by chemical evolution.
- 4Miller (1953): electric discharge in CH₄, H₂, NH₃ and water vapour in a closed flask gave amino acids.
- 5First non-cellular life about 3 billion years ago; first cellular life about 2000 mya.
- 6Darwin sailed on H.M.S. Beagle; Alfred Wallace reached similar conclusions in the Malay Archipelago.
- 7Darwinian fitness means reproductive fitness only.
- 8Haeckel proposed the embryological evidence; Karl Ernst von Baer disproved it.
- 9Homologous (divergent evolution): forelimbs of whale, bat, cheetah and human; vertebrate hearts and brains; thorn of Bougainvillea and tendril of Cucurbita.
- 10Analogous (convergent evolution): wings of butterfly and bird; eye of octopus and mammal; flippers of penguin and dolphin; sweet potato and potato.
- 11Industrial melanism in England: 1850s mostly white-winged moths; 1920 mostly dark-winged. Lichens indicate pollution.
- 12Herbicide, pesticide, antibiotic and drug resistance are evolution by anthropogenic action.
- 13Adaptive radiation: Darwin's finches of the Galapagos; Australian marsupials. Placental wolf and Tasmanian wolf show convergent evolution.
- 14Darwinism rests on branching descent and natural selection; Lamarck proposed use and disuse (giraffe neck).
- 15Hugo de Vries (evening primrose): mutation, saltation; mutations are random and directionless.
- 16Hardy-Weinberg: p + q = 1 and p² + 2pq + q² = 1; AA = p², Aa = 2pq, aa = q².
- 17Five factors disturb H-W equilibrium: gene migration/gene flow, genetic drift, mutation, genetic recombination, natural selection.
- 18Selection types: stabilising (mean favoured), directional (one side), disruptive (both ends).
- 19Coelacanth, a lobefin thought extinct, was caught in South Africa in 1938; dinosaurs vanished about 65 mya.
- 20Brain sizes: Homo habilis 650-800 cc, Homo erectus about 900 cc, Neanderthal man 1400 cc.
Common traps
Where marks are lost
Calling sweet potato and potato homologous.
They are analogous: sweet potato is a root, potato a stem, modified for the same job of storage.
Calling the Bougainvillea thorn and Cucurbita tendril analogous.
They are homologous: both are modified stem structures, the same origin used for different jobs (divergent evolution).
Saying homology comes from convergent evolution.
Homology comes from divergent evolution (common ancestry); analogy comes from convergent evolution.
Saying the white moths were completely wiped out after industrialisation.
No variant is completely wiped out; the proportions reversed, and white moths stayed common in rural areas.
Treating fitness as strength or long life.
Darwinian fitness is reproductive fitness: leaving more progeny.
Saying the vestigial gill slits prove embryos pass through adult stages of ancestors.
Von Baer rejected Haeckel's idea: an embryo never goes through the grown-up stage of another animal.
Giving Aa as pq in Hardy-Weinberg.
Heterozygotes are 2pq, because Aa can arise two ways (A from either parent).
Leaving genetic recombination out of the five H-W factors, or adding 'inbreeding'.
The five: gene flow, genetic drift, mutation, recombination of genes, natural selection.
Mixing up the brain sizes of human ancestors.
They rise in order: habilis 650-800 cc, erectus about 900 cc, Neanderthal 1400 cc.
Saying Ramapithecus was more ape-like.
Ramapithecus was more man-like; Dryopithecus was more ape-like.
Key terms
20 terms
- Panspermia
- The idea that units of life (spores) reached earth from outer space.
- Spontaneous generation
- The disproved idea that life arises from decaying non-living matter.
- Chemical evolution
- Formation of diverse organic molecules from inorganic ones, before life appeared.
- Special creation
- The belief that species were created as they are, diversity never changes and earth is about 4000 years old.
- Natural selection
- Nature favouring individuals whose heritable traits let them leave more offspring.
- Fitness
- In Darwin's sense, reproductive fitness: the ability to leave more progeny.
- Fossil
- Remains of the hard parts of an organism preserved in rock.
- Paleontological evidence
- Evidence for evolution from fossils in rock layers of different ages.
- Homologous organs
- Organs with the same basic structure and origin but different functions.
- Analogous organs
- Organs with different structure but similar function.
- Divergent evolution
- One ancestral structure developing in different directions for different needs.
- Convergent evolution
- Different structures evolving towards the same function, often in similar habitats.
- Industrial melanism
- The rise of dark-winged moths where soot darkened tree trunks.
- Adaptive radiation
- Many species evolving from one ancestral stock in one area, spreading into different habitats.
- Saltation
- De Vries's single-step large mutation causing speciation.
- Gene pool
- All the genes and their alleles in a population.
- Genetic equilibrium
- Allele frequencies staying constant across generations (Hardy-Weinberg equilibrium).
- Genetic drift
- Change in allele frequencies by chance.
- Founder effect
- A drifted population, much changed in allele frequency, founding a new group that may become a new species.
- Gene flow
- Repeated gene migration between populations.