What is the structure in the diagram?

When organisms are classified ,they are given a two part name

Consider darwin's first writings on the theory of natural selection. an important point of darwin's essay on the principle of population, written in 1798, was a peer's observation that in nature plants and animals produce far more offspring than can survive, this observation can be attributed to a) charles lyell. b) thomas malthus. c) jean-baptiste lamarck. d) johann friedrich meckel.

In which situations is the principle of cross-cutting relationship useful in determining relative age?