Here's a breakdown:
* Common ancestor: A single organism from which all members of a group descended.
* Shared characteristics: These can include physical traits, genetic makeup, developmental patterns, or even behavioral tendencies. These shared characteristics are passed down through generations.
* Phylogenetic relationships: The study of evolutionary relationships between organisms is called phylogeny. This helps us understand how different groups are related and how they evolved from common ancestors.
Examples:
* All mammals: Share a common ancestor that lived millions of years ago. They have shared characteristics like mammary glands, hair, and warm-bloodedness.
* All primates: Share a common ancestor and have traits like grasping hands and feet, large brains, and a more complex social structure.
* All flowering plants: Share a common ancestor and have distinct structures like flowers and fruits.
Key points to remember:
* Groups of common descent are organized hierarchically, from smaller groups within larger ones. For example, all humans belong to the primate group, which is part of the mammal group.
* The concept of common descent is fundamental to evolutionary theory. It explains how the diversity of life on Earth has evolved over millions of years.
* The term "common descent" is closely related to the concept of "phylogeny". Phylogenetic trees show how different species are related based on their shared ancestry.
Understanding groups of common descent helps us make sense of the amazing diversity of life on Earth and how everything is interconnected.