What term describes a group of organisms believed to have evolved from a common ancestor?

A clade is a term used in phylogenetics to describe a group of organisms that includes an ancestral species and all its descendants. This definition emphasizes evolutionary relationships and illustrates how species are interconnected through common ancestry. Clades are often represented in phylogenetic trees, where branches depict the divergence of species from their common ancestor over time.

The concept of a clade allows scientists to classify organisms in a way that reflects their evolutionary history rather than just superficial characteristics. This is particularly useful in understanding the complexities of evolution and the relationships that exist among various organisms in the natural world.

In contrast, the other terms do not capture this concept of shared ancestry as effectively. A species generally refers to a group of organisms capable of interbreeding and producing fertile offspring, while family and genus are classifications in the hierarchical system of taxonomy that group species based on broader characteristics rather than direct descent. Thus, a clade is the most accurate term for describing a group of organisms evolved from a common ancestor.