In 1683, he discovered bacteria. This great discovery is the building blocks of the cell theory. He stated in his theory that the cell is the basic unit of all living things. He also helped disprove the theory of spontaneous generation by showing that heat destroys the “infusoria” needed for putrefaction.

Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani, spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

While the hypothetical process of spontaneous generation was disproved as early as the 17th century and decisively rejected in the 19th century, abiogenesis has been neither proved nor disproved.

Rudolf Virchow

Robert Hooke

Anton Van Leeuwenhoek

However, molecular systematics showed prokaryotic life to consist of two separate domains, originally called Eubacteria and Archaebacteria, but now called Bacteria and Archaea that evolved independently from an ancient common ancestor.

Theodor Schwann

Antonie van Leeuwenhoek used single-lens microscopes, which he made, to make the first observations of bacteria and protozoa. His extensive research on the growth of small animals such as fleas, mussels, and eels helped disprove the theory of spontaneous generation of life.

Ernest Rutherford’s

Prokaryotes are organisms whose cells lack a nucleus and other organelles. Most prokaryotes are small, single-celled organisms that have a relatively simple structure. Prokaryotic cells are surrounded by a plasma membrane, but they have no internal membrane-bound organelles within their cytoplasm.

The three parts of the cell theory are:

• All living things are composed of cells.
• Cells are the basic units of structure and function for living things.
• All cells come from pre-existing cells. Also, organisms grow by “adding on more cells” NOT by increasing the size of their cells.