Speciation and Breeding
- Created by: Tomos Foulkes
- Created on: 21-04-16 15:25
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- Speciation and Breeding
- Allopatric speciation
- Populations of a species become geographically isolated. (More common than sympatric)
- Selection and genetic drift will act differently creating genetic differences between the two new species
- The 'Island Rule'
- Island endemics: species unique to a particular island
- Gigantism & Dwarfism (smaller species evolve larger bodies and vice versa)
- Factors effecting immigration / extinction: island size & distance from mainland
- Population divergence: geographical barrier, population come together again but do NOT interbreed (now 2 new species)
- Environmental gradients: gradual change in abiotic factors over space (or time)
- Ecotypes - genetically distinct population within a species which is adapted to specific env. conditions - ultimatley can become their own species
- e.g. Festuca ovina (grass) Gwynedd, Wales and Dorset, England
- Ecotypes - genetically distinct population within a species which is adapted to specific env. conditions - ultimatley can become their own species
- Mountain diversity: Species migration limited by several factors - area, rainfall, resource diversity, productivity, temperature etc.
- e.g. Arctic - Alpine taxon (Ben Lawes)
- Sympatric speciation
- Polyploidy
- Offspring produced with twice the normal number of chromosomes
- More common in plants than animals
- Tetraploid individual cannot mate with diploid individual creating reproductive isolation
- Tetraploidy can fertilize itself and create offspring e.g.
- Autopolyplody & Allopolyploydy
- Populations of a species that share the same habitat become reproductively isolated from each other
- Host shiftt
- Polyploidy
- Parapatric Speciation
- Extremely rare
- Populations separated by an extreme change in habitat
- Ranges do NOT significantly overlap but are immediatley adjacent to each other - do not occur together except in a narrow contact zone
- Geographical distribution as oppose to sympatry (same area) and allopatry (two cases of distinct areas)
- Allopatric speciation
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