BIOLOGY TIMELINE

1595 – 1610

Hans and Zacharias Janssen

Janssen is known for his microscope which was finished between 1595 - 1610. He is also accredited as the inventor of the first true compound microscope. This microscope could magnify 9-fold. This scientist indirectly contributed to the cell theory. By creating the microscope that allowed Robert Hooke to discover the first cells, Janssen gave him the tool he needed to make an innovative discovery.

1595 - 1610

1665

Robert Hooke

In 1665, Robert Hooke, an English scientist, made the revolutionary discovery of the cell. Using a primitive compound microscope, Hooke was able to see what he believed was a plant cell, though Hooke was looking at dead cell walls that belonged to a piece of cork. He only saw cell walls as this was dead tissue. He coined the term "cell" for these individual compartments he saw.

1665

1668

Francesco Redi

He did an experiment to determine if rotting meat turned into flies. He found that meat cannot turn into flies and only flies could make more flies. This was an important experiment because it helped to disprove the theory of spontaneous generation.

1668

1673

Anton van Leeuwenhoek

Leeuwenhoek was the first Dutch microscopist to observe microorganism from a lake as well as the stinger of bees. In 1670, Leeuwenhoek significantly improved the quality of microscope lenses to the point that he could see the single-celled organisms that lived in a drop of pond water. He called these organisms “animalcules,” which means “miniature animals.” In 1673, he contributed to the cell theory by being the first to prove that a living thing has cells. Additionally, around 1720 Leeuwenhoek also was credited with discovering a type of bacteria, that of which is called protists. He also discovered a simple microscope that was powerful enough to see the first living cell.

1673

1833

Robert Brown

In 1833, Robert Brown, an English botanist was the first to recognize the nucleus (a term that he introduced when he discovered these) as an essential constituent of living cells (1831). Brown recognized the general occurrence of the nucleus in these cells and apparently thought of the organization of the plant in terms of cellular constituents.

1833

1838

Matthias Schleiden

By 1838, Matthias Schleiden, a German botanist continued to analyze plants and their cells through a compound microscope. Matthias Schleiden stated that the different parts of the plant organism are composed of cells, and that cells are the basic building blocks of all plants. He proposed that cells were a fundamental unit of life and that all living things have them.

1838

1839

Theodor Schwann

In 1839, Theodore Schwann became interested in Schleiden's research. Schwann was curious as to whether animals had cells like plants had. Hence, Schwann blended both statements into one theory which said 1) All living organisms consist of one or more cells and 2) The cell is the basic unit of structure for all living organisms. And he proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel. He was the first one to state that all animals are composed of cells.

1839

1840

Albrecht von Roelliker

In 1840, Albrecht von Roelliker discovers that sperm and eggs are also cells.

1840

1850

Louis Pasteur

In 1850, Louis Pasteur created an experiment that showed cells could only be formed from pre-existing cells. This scientist also contributed to the cell theory by supporting the idea that cells are products of other cells.

1850

1855

Rudolph Virchow

In 1855, Rudolph Virchow, a German physiologist/physician/pathologist contributed to the cell theory by proving the third statement to be true; cells come from other cells. Virchow completed the third statement prominent in the Cell Theory. Through extensions research, Virchow supported the claim that all cells arise from other cells. Virchow also stated that diseased cells can be a product of healthy ones. Also, He is cited as the first to recognize leukemia cells.

1855