<span>Ethology is a branch of zoology concerned with the study of animal behavior. Ethologists take a comparative approach, studying behaviors ranging from kinship, cooperation, and parental investment, to conflict, sexual selection, and aggression across a variety of species.</span>
<span>Studying the changes in densities of pocket gophers when large herbivores such as elk are excluded from mountain forests would be an example of studying ecology at the community level.
A community refers to a group of organisms of various species that live in the same location and interact with each other. So, if this scientist is observing gophers and elks, they are looking at the level of communities, not anything more or less.
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Answer:
Excess nitrogen can cause over-stimulation of growth of aquatic plants and algae. Excessive growth of these organisms, in turn, can clog water intakes, use up dissolved oxygen as they decompose, and block light to deeper waters. So few organisms live in these conditions or even can suffocate and die.
The red-green color blindness is a recessive X-linked trait. The females are not affected unless both the X chromosomes have the affected allele. Mostly, the females are the carriers, and the males are affected as they have only one X chromosome. In the given pedigree, the father of Irene have the normal allele, while her mother is a carrier. However, Irene is neither a carrier nor affected. This means that she carries normal alleles on both X chromosomes. Hence, her allele combination is 
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