Answer:
Firstly,the theory of common descent states that all living organisms are descendants of a single ancestor.
The chemical make-up and biochemical process of all organisms are very similar. For example, all organisms
• are build up of the same types of complex molecules- carbohydrates, lipids, protein, and nucleic acids;
• use ATP as the immediate source of energy for metabolic reactions; and
• use the same materials and processes for storing, expressing and transmitting genetic information.
The theory of common descent states that all living organisms are descendants of a single ancestor.
Thus, the Theory of Common Descent helps to explain why species living in different geographical regions exhibit different traits, some traits are highly conserved amongst some animal classifications like vertebrates or tetrapods; seemly different species like birds and reptiles share inherited physical and genetic traits, and successfully adapted organisms typically produce more offspring.