Darwin concluded that the finches all shared a common ancestor but had developed different beak structures. The second sentence best describes as an ecosystem.

Explanation:

When Charles Darwin traveled to the Galapagos Islands, he observed 14 distinct varieties of finches on the islands Darwin also observed that each finch variety ate a different type of food and lived in a slightly different habitat from the other finches, Darwin concluded that the finches all shared a common ancestor but had developed different beak structures. The second sentence best describes as an ecosystem.
An ecosystem is a huge group of living organism such as plants,animals, micro-organisms in a particular area.
An ecosystem is a community of living organisms related with the nonliving components in the environment, together interacting as a system.
its abiotic constituents, includes minerals, climate, soil, water, sunlight, and all other nonliving elements, and its biotic constituents, consists of all its living members.