Which of the statements about variation is not true? select one:
a. variation is differences in the size, shape, or color etc. of a particular species.
b. variation in a particular species allows for natural selection process to take place.
c. the amount of variation of a particular trait does not affect how quickly a trait evolves.
d. variation is necessary for a trait to evolve over time.

c. The amount of variation of a particular trait does not affect how quickly a trait evolves.

Explanation:

Variation is the diversity observed within a species. In a species all the organisms are not identical. They can vary in different characteristics like shape, size or colour. Variation can lead to natural selection because a particular variant of a trait can be favoured over the other ones and eventually  it becomes dominant in the population.

Evolution of a trait is also effected by the amount of variation present in that trait. More the variation, more different will be its response to the changing environment and more time can be required to incorporate these changes within an organism.

1. a tropical dry forest carries out more rapid nutrient cycling

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."