Final answer:
Common descent refers to the idea that all living organisms on Earth share a common ancestry, supported by evidence from genetics, fossils, and shared characteristics. It helps us understand the interconnectedness and diversity of life.
Step-by-step explanation:
Common descent refers to the idea that all living organisms on Earth share a common ancestry. This means that all organisms are linked through a series of evolutionary changes from a single ancestor. Scientists use evidence from genetics, fossils, and shared characteristics to support the concept of common descent. For example, comparing the genetic code of different species can reveal similarities, indicating a shared ancestor. The concept of common descent helps us understand the interconnectedness and diversity of life on Earth.