AP BIOLOGY

Detailed explanation-1: -First proposed by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838, the theory that all plants and animals are made up of cells marked a great conceptual advance in biology and resulted in renewed attention to the living processes that go on in cells.

Detailed explanation-2: -The classical cell theory was proposed by Theodor Schwann in 1839. There are three parts to this theory. The first part states that all organisms are made of cells.

Detailed explanation-3: -Schwann concluded three things that became vital components of the cell theory. First, Schwann concluded that both plants and animals were composed of cells. Second, these cells have independent lives. Third, these independent lives are subject to the organism’s life.

Detailed explanation-4: -By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. 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.