What defines a clade in evolutionary biology?

A clade in evolutionary biology is defined as a group of organisms that includes an ancestor and all of its descendants, which means that they share a common ancestor. This concept reflects the idea of common descent, where species can be traced back to a specific point in evolutionary history. Clades are often depicted in phylogenetic trees, where branches represent the evolutionary pathways and relationships among different organisms. By focusing on shared ancestry, clades help illustrate the evolutionary connections and similarities among diverse organisms, reinforcing the understanding of the tree of life.

The other options do not accurately capture the definition of a clade. A random selection of species does not take into account evolutionary relationships or common ancestry. A sequence of DNA mutations pertains to genetic changes within individuals or populations but does not define clades in terms of evolutionary lineage. An individual organism also does not represent a clade since it cannot encompass multiple descendants necessary for that classification. Thus, the emphasis on common ancestry clearly distinguishes a clade as a specific group within evolutionary biology.