Question

All the plants and animals are composed of cells and the cell is the basic unit of life. Which theory states this?

Answer 1

Schleiden and Schwann's work:

1. In 1838, Matthias Schleiden, a German botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant.
2. Schwann (1839), a British Zoologist, studied different types of animal cells and he proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.
3. Schleiden and Schwann together formulated the cell theory.
4. This theory, however, did not explain how new cells were formed.
5. Rudolf Virchow in 1855 first explained that cells divided and new cells are formed from pre-existing cells.

Cell theory:

1. All organisms are made up of cells.
2. New cells are formed from preexisting cells
3. Cells provide the basic units of functionality and structure in living things.