Polygenic traits are those traits that are controlled by more than one gene. Such traits may even be controlled by genes located on entirely different chromosomes. Human height, eye and hair color are examples of polygenic traits. Skin color is another polygenic trait for humans and a variety of other animals.
A. DNA mutation (i think)
A rain forest would have the most species diversity if you are talking about complex eukaryotic organisms (reptiles, mammals etc), though the polluted lake would have the most simple prokaryotic organisms ( bacteria, protists, fungi etc.)
