explain the different ways in which a new species can evolve as a result of natural selection?

Question

give examples of species that illustrate and support your conclusion

Answer 1

Look at molluscs especially the gastropods. All animal bodies use the basic torus form; mouth at one end anus at the other. Snails still need to excrete, but this is not good inside a shell. So snails contort or twist in their growth. With the left half dominating the right half, they put in a 180 so the anus and mouth both face out of the shell. Snails, stuck with the same basic body tube we have, underwent one re-organization. A simple first mutation that produced asymmetry in a bilateral development allowed those ur-snails to hide under their shell in another way.
http://icb.oxfordjournals.org/cgi/content/abstract/46/2/134
http://www.palaeos.com/Invertebrates/Molluscs/Mollusca.htm
Imagine a bilateral limpet-like mollusc juvenile that grows one side of its shall faster than the other, a spiral forms as the snail grows. There is still shelter from predators and the shell still enlarges as the animal grows. The contortion keeps the mouth and anus facing the exterior so the shell remains habitable.
This kind of coiling shell appears repeatedly in tube worms as well as molluscs. Most coil to the right but some coil to the left but rarely to both in one species. http://www.applesnail.net/content/anatomy/shell.php
The additional space allows the snail to pull back into the shell for more shelter from predators than a simple shield shell provides.
http://books.google.com/books?id=jp4uAYEx_goC&pg=PA143&lpg=PA143&dq=advantages+spiral+mollusc+shell+shield+shell&source=web&ots=YOXsTziniC&sig=RnNRjirf95s9JIvI5YyoWPdW9iw
The compact spiral of a snail is strong but balanced over the body. Once established further mutations gave rise to the numerous snail varieties.
Because they had shells and a life style that required little mobility the mutation that would be fatal in other organisms simply provided a variant body form that led to further adaptations and refinements.

Answer 2

Too broad a question. Go here and do research.

http://www.talkorigins.org

http://www.aboutdarwin.com