Question

what is difference between speciation and variation ?

Answer 1

Variation in evolution usually refers to variation of genes at a particular loci. This differs from diversity which is the total of genetic differences within a population. Speciation is the reproductive isolation of a subset of a population.

A lot of your plants die, and whatever remains gives rather small and mostly bland fruits. Once in a long while though, you get that odd fruit which is slightly bigger and tastes better. You are intelligent enough to notice that, and start saving up on its seeds and planting more of the tasty ones. Voila, you have just discovered variation in the population and are now trying to impose selection on the population.

One day you notice that some particular plants in the forest tend to survive more than the others. You know the basic principles of plant breeding and you want your crop to live longer and have tasty fruits. So you try crossing these plants to get a new one which will have both their properties.

This time though, you fail. Miserably. Every time you try to cross the wild plant with the plant in your crop, there is no offspring.

, you have just encountered speciation