A marine biologist compares 2 samples of reef-building coral colonies collected from various ...

Under the typological definition of a species, these colonies are not members of the same species, since their morphology differs. However, these 2 colonies may not necessarily be different species, since coral is known to show great variability in appearance because of environmental differences (for example, if the species grows in rough or calm water). Under the biological species definition, if individuals are crossed and produce viable offspring, then they are members of the same species. The marine biologist might conduct experiments to determine if the 2 colonies are cross-fertile, or use DNA techniques to compare genes as a first step in answering this question.