AP BIOLOGY

Detailed explanation-1: -The cell theory states that all biological organisms are composed of cells; cells are the unit of life and all life come from preexisting life. The cell theory is so established today that it forms one of the unifying principles of biology.

Detailed explanation-2: -The theory of evolution is quite rightly called the greatest unifying theory in biology because it explains the origin of life and its gradual change over the time which includes morphological, developmental and genetic level.

Detailed explanation-3: -Four unifying principles form the foundation of modern biology: cell theory, evolutionary theory, the gene theory and the principle of homeostasis. These four principles are important to each and every field of biology.

Detailed explanation-4: -Cell theory-This is crucial for us understanding biology because cells form the basis of all life. We can have unicellular organisms, like bacteria, like yeasts. [And] cell division, the division of a cell from one, to two, to four, forms the basis of growth and development of all living things.

Detailed explanation-5: -The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory.