What is one key principle of the unity of life?

The key principle of the unity of life is that all forms of life are made of cells. This concept is foundational in biology, emphasizing that cells are the basic unit of life. Regardless of the vast diversity among different organisms, from single-celled bacteria to complex multicellular organisms like plants and animals, all share the characteristic of being composed of cells. This principle reinforces the idea that all living things have a common structural foundation, which is critical for studying the similarities and differences in biological functions and processes among diverse life forms.

Other concepts, such as genetic makeup and modes of reproduction, vary greatly among organisms and do not universally apply to all forms of life. The concept of adaptation also varies in effectiveness and ability across species, further separating it from the idea of a unifying characteristic like cellular composition. Thus, emphasizing that all life forms are ultimately cellular in nature highlights a fundamental shared trait that underlines biological unity.