Natural selection requires genetic variation, competition for limited resources, overproduction of offspring, and unequal reproductive success. the subset of finches that is capable of eating large seeds, while many others eat small seeds, is an example of which requirement?

Genetic variation

Explanation:

Darwin studied that different populations of finches on Galapagos island that are descended from the same species. Some species are evolved to eat nuts and large seed, some eat small seeds and some feed on insects and nectar.

So genetic variation occurred in different populations of finches which enabled them to bring changes in their beak according to the food resource they have chosen to feed on.  

So in Darwin's finches, genetic variation leads to new species which is a type of natural selection. Therefore subset of finches that can feed on large seeds and small seeds is an example of genetic variation.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

here's your answer.