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MICRO-EVOLUTION

MICRO-EVOLUTION. MECHANISMS OF EVOLUTION WITHIN POPULATIONS GENETIC DRIFT GENE FLOW MUTATION NON-RANDOM MATING NATURAL SELECTION. Micro-evolution: GENETIC DRIFT. FOUNDER PRINCIPLE e.g. Early Dutch Settlers in SA or new arrivals on isolated islands Small population (Founders)

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MICRO-EVOLUTION

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  1. MICRO-EVOLUTION MECHANISMS OF EVOLUTION WITHIN POPULATIONS • GENETIC DRIFT • GENE FLOW • MUTATION • NON-RANDOM MATING • NATURAL SELECTION Annemarie Gebhardt 2008

  2. Micro-evolution: GENETIC DRIFT • FOUNDER PRINCIPLE • e.g. Early Dutch Settlers in SA or new arrivals on isolated islands • Small population (Founders) • Limited alleles in genome • Change in gene frequency • Some alleles become more prominent, e.g. • High cholesterol & porphyria • BOTTLENECK EFFECT • e.g. Cheetah populations in Africa and India • Chance events drastically reduced size of population • Loss of genetic diversity • Reduced genetic vigour • Inbreeding, disease prone, etc. Annemarie Gebhardt 2008

  3. GENE FLOW (Gene migration) • Migration of genes between populations • Closely related species or isolated populations mate / cross pollinate • Out breeding – resulting in hybrids • Fertile hybrids may evolve to new species • Common amongst SA Aloe species Annemarie Gebhardt 2008

  4. MUTATIONS • Random error in gene configuration • Environmental stress e.g. radiation, virus, extreme temperatures, chemicals, etc. • Somatic mutations – not inherited • Germline mutations may lead to speciation if new phenotype is advantageous • Main cause of polyploidy in plant species Annemarie Gebhardt 2008

  5. MUTATION TYPES LOCATION RESULTING NATURE LETHAL – both alleles thus homozygous – early death (foetus or young) NEUTRAL – no effect on next generation, until conditions change FIXED – advantageous to speciation (macro – evolution) • Chromosomal • DNA or in GENE(S) Caused by a single mutated gene ! Annemarie Gebhardt 2008

  6. GENE MUTATIONS Annemarie Gebhardt 2008

  7. NON-RANDOM BREEDING INBREEDING • Mating between relatives • Increases homozygosity • Harmful recessive genes become more prominent • May cause disorders e.g. • Haemophilia, Cystic fibroses, Muscular dystrophy, Hyper cholesterolemia ASSORTIVE BREEDING e.g. • Tall X Tall • Selecting mates with similar phenotypes Annemarie Gebhardt 2008

  8. NATURAL SELECTION • May cause rapid change in population characteristics e.g. in example below: • Some examples include the British Pepper moth; camouflage in animals; mimicry; pesticide- , antibiotics-, and antiviral resistance Annemarie Gebhardt 2008

  9. Natural Selection in Action Classic Pepper Moth Experiment Annemarie Gebhardt 2008

  10. ARTIFICIALSELECTION Annemarie Gebhardt 2008

  11. MISCONCEPTIONS Natural selection responds to a need Natural Selection = Evolution WRONG AGAIN ! WRONG !! Annemarie Gebhardt 2008

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