Specialization within Species

Thoughts

The idea of mobility makes me think about people of Upper Egypt and how their mingling with Egyptians from the Nile Delta area creates a sort of hybridization which is healthy. On the other hand, people who live in Siwa and have been more or less in isolation from the external world for thousands of years have been forced to adapt more to their environment. Also people who live in Aswan in Egypt and are Nubians might have less genetic variation and are more adapted to their environment.

Digest

• The term species will be defined in the next section.
•  An ecotype was coined in 1922 by Göte Turesson for plant populations "to describe genetically determined differences between populations within a species that reflect local matches between the organisms and their environments."
• Only if the forces favoring divergence are strong enough to counteract the mixing and hybridization of individuals from different sites and  there is sufficient heritable variation on which selection can act evolution then forces the characteristics of populations to diverge from each other.
• Immobile organisms become differentiated most notably while mobile organisms are less exposed to the forces of natural selection and therefore do not have to match themselves to a fixed environment as much as immobile organisms have to.

Questions

1. Why is there no continuum of species along a spectrum of variation among organisms?
2. What is the definition of a species?
3. What about variation within the same species according to the environment they live in?