02 Species and Speciation

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02 Species and Speciation

  1. 1. Species and Speciation ALBIO9700/2006JK
  2. 2. Species:• A group of organisms, with similar morphological , physiological , biochemical and behavioural features, which can interbreed to produce fertile offspring , and are reproductively isolated from other species ALBIO9700/2006JK
  3. 3. ALBIO9700/2006JK
  4. 4. Classification• Taxonomy – the study of the classification of organisms• Homologous features – shared features between different organisms• Binomial – two-word Latin name for every species• Phylogeny – the evolutionary history of living organisms ALBIO9700/2006JK
  5. 5. Classification (cont) ALBIO9700/2006JK
  6. 6. New species usually develop due to:• geographical isolation (allopatric speciation )• reproductive isolation (sympatric speciation ) ALBIO9700/2006JK
  7. 7. Allopatric speciationStart with an interbreedingpopulation of one species. The population becomes divided by aphysical barrier such as water,mountains, desert, or just a largedistance. This can happen when some ofthe population migrates or is dispersed,or when the geography changescatastrophically (e.g. earthquakes,volcanoes, floods) or gradually (erosion,continental drift). ALBIO9700/2006JK
  8. 8. If the two environments (abiotic or biotic) aredifferent (and they almost certainly will be),then the two populations will experiencedifferent selection pressures and will evolveseparately. Even if the environments aresimilar, the populations may change byrandom genetic drift, especially if thepopulation is small.Even if the barrier is removed and the twopopulations meet again, they are now sodifferent that they can no longer interbreed.They are therefore reproductively isolatedand are two distinct species. They may bothbe different from the original species ,if it still exists elsewhere. ALBIO9700/2006JK
  9. 9. Sympatric speciation• Genetic isolation• Formation of a new species can take place in the same geographical area , e.g. mutations may result in reproductive incompatibility• A new gene producing, say, a hormone, may lead an animal to be rejected from the mainstream group, but breeding may be possible within its own groups of variants• When this mechanism results in the production of a new species it is known as sympatric speciation• Polyploidy, autopolyploid, allopolyploids? ALBIO9700/2006JK
  10. 10. Sympatric speciation• Genetic isolation• Formation of a new species can take place in the same geographical area , e.g. mutations may result in reproductive incompatibility• A new gene producing, say, a hormone, may lead an animal to be rejected from the mainstream group, but breeding may be possible within its own groups of variants• When this mechanism results in the production of a new species it is known as sympatric speciation• Polyploidy, autopolyploid, allopolyploids? ALBIO9700/2006JK

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