Describe how new species of organism may arise

The process by which new species arise in known as speciation. Speciation to occur their must genetic isolation of a pollution for enough time to allow the new species to arise. Mutation and natural selection take place independently isolated populations and each may lead to formation of new distinct species.

Population and genetic isolation may achieved in the following ways

  • Geographical/ecological isolation

This is when physical barrier such as mountain, river or other water bodies prevents the population from mixing.


  • Reproductive isolation

Populations that may not be ecologically separate, are not able to interbreed. This can e due lack of attraction between individuals in a population, non-corresponding genitalia, development of immune destruction of sperms. Inability of the zygote to develop.

  • Behavioral isolation

This may be due to failure of courtship behavior to stimulate sexual activity in another

  • Genetic isolation

Even though mating is possible, fundamental differences in genetic constitution may prevent reproduction being successful. For instance, pollen grains of one plant may fails to germinate on the stigma of another. Sometimes offspring are produced but hybrid may be sterile and fail to reproduce.


  • the use of seeds and other planting materials are common methods in plant propagation. Using named examples, give advantages and disadvantages of each method
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