Questions 1 and 2 are based on this passage

Ecologists study how millions of species share the world, rather than take on the whole planet at once; they generally focus on a single ecosystem, be it a prairie, a tidal flat, or a sand dune. Even within those limits, they are frustrated by porous frontiers. As a result, ecologists have done some of their most important work on islands, nature’s own isolated laboratories, which may be colonized only a few times over the course of millions of years. On them, ecologists have figured out how the size of a given habitat determine how many species it can support. They have then applied that knowledge to the mainland, showing how fragmented ecosystems become like archipelagoes, where extinctions can strike.