Tree of life theories are associated with different aspects of life such as religion, science, mythology, philosophy, etc. The meaning associated with the tree of life can change in different contexts. In various mythologies, theologies, and philosophies around the world, the tree of life is used as a motif or symbol to represent many different qualities. The concept of the tree of life is also used in reference with the phenomenon of evolution. The phenomenon is used metaphorically to explain the theory of common descent. Darwin's tree of life is an important theory to consider in this area of study. The meaning of tree of life can be explained in different ways with the help of different knowledge sources. Tree of life and tree of knowledge are two forms of the world tree/cosmic tree. 'Tree of life' connects different life forms, whereas 'Tree of knowledge' connects the heaven and underworld.