Natural Selection and Adaptive Evolution in Large Populations Flashcards
Global threats
Climate change- local, regional and international.
Introduced pests- Increased predation pressure.
Introduced competitors- Red queen hypothesis.
New parasites- Evolve or move into new hosts, switch hosts and emerging infectious diseases.
Types of adaption
1) Physiological eg. Haemoglobin levels change in response to altitude
2) Behavioural eg. Shift in wintering areas of birds due to temperature
3) Genetic - Evolutionary change through natural selection
Adaptive evolution
‘Differential reproduction and survival of different genotypes’ genotypic diversity must be present.
Importance of adaptive evolution in conservation
1)Allows endangered species to overcome new challenges
2)Need to ensure recovery populations don’t loose this ability
3)Need to guard against genetic adaptation to captivity
4) Most endangered species are not in core of historic range, must adapt to marginal habitats.
Warfarin resistance in rats.
Selection in adaptive evolution.
Changes in allele frequency caused by:
1) Random chance (drift)
2) Migration of individuals from elsewhere
3) Mutation (happens very slowly)
4) Selection, only force that drives adaptive evolution
Selection acts on fitness
Selection changes genotype frequencies. If genotype has high fitness then it is selected for, and if a genotype has low fitness it is selected against- lowers in frequency.
Selection goes both ways
Selects against deleterious alleles and for favourable ones. Example, Melanism in moths.
How does selection operate on quantitive characters?
Quantitive characters are a product of:
1) Multiple genetic loci
2) Environmental effects
Selection acts on mean and variance of phenotypic characters, not allele frequencies.
3 forms of selection on quantitive characters
1) Stabilising (Favours phenotypic intermediates, no change in mean)
2) Directional (Favours phenotypes towards one direction)
3) Disruptive (Favours both phenotypic extremes, no change in mean)
