Final answer:
A common ancestor is an ancestor that is shared by multiple evolutionary lines of descent.Option 4 is the correct answer.Common ancestors, shared among evolutionary lines, connect diverse species, exemplified by the shared lineage of humans and chimpanzees.
Step-by-step explanation:
A common ancestor is defined as an ancestor that is shared by multiple evolutionary lines of descent. This means that different species can trace their evolutionary origins back to a common ancestor. For example, humans and chimpanzees share a common ancestor that lived around six million years ago, even though they are not direct descendants of each other.
A common ancestor serves as a pivotal concept in evolutionary biology, representing an ancestral organism shared by diverse lines of descent. This shared ancestry implies that various species can trace their evolutionary roots to this common progenitor. A striking example is the shared common ancestor between humans and chimpanzees, dating back around six million years. Despite the distinct evolutionary trajectories leading to these species, their shared ancestry highlights the interconnectedness of all life forms and underscores the evolutionary unity that binds different organisms through their historical lineage, shaping the intricate web of biodiversity we observe today.