Genetic diversity refers to the various genes and their respective alleles present in all the populations of a species. In the given image, the second image from the left side has one yellow, two blue, one red and one green dot. So, it has a total of four types of genes (yellow, red, green and blue) as indicated by dots. Since this circle has the maximum number of different types of dots, it represents the population of the species with maximum genetic diversity.
Ans: Cells are so small because it allows them to have a better surface area to volume ratio. This makes it much easier for the cell to bring in necessary nutreints and excrete wastes. Also the smaller the cell is, the less time it takes to replicate the small cell as opposed to a bigger cell.