What is common descent in biology and how does it explain the evolutionary relationships between different species?

Common descent in Biology is the idea that all living organisms share a common ancestor. This theory explains the evolutionary relationships between different species by suggesting that all organisms have evolved from a single common ancestor over time, leading to the diversity of life we see today. By studying similarities in DNA, anatomy, and other characteristics, scientists can trace the evolutionary history of species and understand how they are related to each other through a process of descent with modification.