Adaptive Radiations in Birds.pptx

Adaptive Radiations in Birds

1. Advanced Ornithology by Maryam R iasat ADAPTIVE RADIATIONS IN BIRDS

2. Evolution Evolution is  the process by which species adapt over time in response to their changing environment T he change in the characteristics of a species over several generations relies on the process of natural selection Simple to complex Sometimes backward, complex to simple

3. Types of Evolution Retrogressive evolution Micro evolution Macro evolution Divergent evolution Convergent evolution Parallel evolution

4. Retrogressive evolution Backward evolution Complex to simple T he formation of simple organs from complex C omplex organisms evolve into simpler forms Flightless birds have evolved from flying birds as they lost the ability to fly e.g. P enguins

5. Micro evolution Variations within species A change that occurs in a population due to changes in allelic frequencies is known as microevolution These are subtle changes that can occur in very short periods of time, and may not be visible to a casual observer These changes may be due to mutations, which can introduce new alleles into a population

6. Macro evolution Speciation Large-scale and visible changes that occur above the level of species are known as macroevolution Macro evolution cannot occur directly, micro evolution leads to macro evolution It is the result of micro evolution taking place over many generations Macro evolution may involve evolutionary changes in two interacting species or it may involve the emergence of one or more new species

7. Divergent evolution Share common ancestor Divergent evolution occurs when two organisms with a common ancestor end up as different species It occurs when related species develop unique traits due to different environments or selective pressures A classic example of divergent evolution is the Galapagos finches, which Darwin discovered  in different environments T he finches beaks adapted differently in different patches

8. Convergent evolution Do not share common ancestor The phenomenon by which two or more species independently evolve a similar trait T he evolution of flight/wings in birds, insects and bats which do not share a common ancestor T hey have separate evolutionary origins, but are superficially similar because they have both experienced natural selection that shaped them to play a key role in flight Analogies are the result of convergent evolution

9. Parallel evolution They may share common ancestors or may not Parallel evolution occurs when independent species acquire similar characteristics while evolving together at the same time in the same space Formation of similar structures in two unrelated species