Anyone know this please help a youngin

Apart of an ecosystem that can restrict the growth of a population is referred to as

Which would be the most useful source of evidence to support mcneill's contention?

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees