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Oct 22, 1580
Jan Baptist van Helmont questions spontaeous generation theory
Jean Baptiste Van Helmont was the first to question the theory of spontaneous generation.He considered that things like sulfur, salt, and mercury were created through chemical processes rather than being preexistent. He did an experiment growing a willow tree for five years and showing it increased in mass while the soil showed a trivial decrease. The theory was that plants grew by eating soil. He concluded that the tree grew by drinking water. http://www.biologyreference.com/Ta-Va/van-Helmont- -
Jansen invents first microscope
Zacharias Jansen invented the first compound microscope. Jansen experimented with multiple lenses placed in a tube that made objects in front of the tube appeared greatly enlarged.
Without the invention of the microscope people would be unable to discover cells or see their structures. http://en.wikipedia.org/wiki/Sacharias_Jansen -
Francesco Redi claims that nonliving things cannot produce living things
Redi postulated that living things do not arise from spontaneous generation. 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.
http://en.wikipedia.org/wiki/Francesco_Redi -
Hooke observes first cell
Robert Hooke looked at a thin slice of cork (oak cork) through a compound microscope and observed tiny, hollow, roomlike structures and called these structures 'cells' because they reminded him of the rooms that monks lived in. He only saw the outer walls (cell walls) because cork cells are not alive. His discovery of cells put the interest in scientists and eventually led to the creation of cell theory.
http://en.wikipedia.org/wiki/Cell_theory -
Leeuwenhoek discovers Protozoa
Anton van Leeuwenhoek a Dutch scientist known as the "Father of Microbiology" was the first to observe protozoa. His studies on lower animals disproved the theory of spontaneous generation.
http://www.britannica.com/EBchecked/topic/334699/Antonie-van-Leeuwenhoek -
Leeuwenhoek discovers bacteria
Anton van Leeuwenhoek discovered bacteria from dental scrapings. Called some of them 'animalcules.' Some of the small 'animalcules' are now called bacteria, which are single-cell organisms. http://en.wikipedia.org/wiki/Cell_theory -
John Needham believes spontaeous generation is possible
Needham was an English microscopist who researched the spontaneous creation of microscopic organisms. He heated samples of broth, which he had previously checked for microorganisms, and then examined the broth again finding again microorganisms. This led him to the conclusion that spontaneous generation was possible. His results were wrong, however, due to the fact that he hadn't heated the broth hot enough to kill the organisms. https://sciactivitiespage.wikispaces.com/Biogenesis+and+Cell+Theor -
Lazzaro Spallanzani proves Needhams claims to be false
Spallanzani disproved Needham's findings about spontaneous generation by using correct procedures that Needham had not. Spallanzani used airtight flasks and proper heating, he determined that soup in a sealed container was sterile and that micro organisms that caused the soup to spoil had entered from the air, giving him results that proved spontaneous generation to be false. http://spontaneous-generation.wikispaces.com/Lazzaro+Spallanzani -
Lorenz Oken classifies animals
Oken created new classifications for animals based on their evolutionary path.Oken made a further advance in the application of the a priori principle, in a book on generation (Die Zeugung), in which he maintained that "all organic beings originate from and consist of vesicles or cells." http://en.wikipedia.org/wiki/Lorenz_Oken -
Robert Brown discovers that cells have a nucleus
Robert Brown was a Scottish botanist who focused his studies on observation of plant cells through a microscope. His observations led him to discover the cell’s nucleus, and was the first scientist to describe the nucleus’ natural occurrence in living organisms’ cells. He gave the nucleus its name, and helped to develop the cell theory by attempting to understand the nucleus' importance in cellular activity. http://www.smithlifescience.com/celltheory.htm -
Schleiden states all plants are made of cells
Matthias Schleiden studied plants and claimed that every plant was made up of cells. He worked with Theodor Schwann to create what is called cell theory. The cell theory states that all living things are made up of one or more cells. http://en.wikipedia.org/wiki/Matthias_Jakob_Schleiden -
Schwann states all organisms (plants and animals) are made of cells
Theodor Schwann studied animal cells and found that all oranisms are composed of cells. He worked with Matthias Schleiden to create cell theory. Schwann also discovered the cells, now known as Schwann cells, that helped disprove the theory of spontaneous generation. http://en.wikipedia.org/wiki/Theodor_Schwann -
Albrecht von Roelliker looks at sperm and egg cells
He realized that sperm cells and egg cells are also cells.
http://www.smithlifescience.com/celltheory.htm -
Hugo von Mohl discovers protoplasm
Hugo studied protoplasm. The concept of protoplasm as the physical basis of life led to the developement of cell physiology. http://en.wikipedia.org/wiki/Hugo_von_Mohl -
Rudolf Virchow studies diseases
German pathologist who stated that all living cells come only from other living cells. Published his aphorism omnis cellula e cellula ("every cell stems from another cell"). Established a relationship between abnormal events in the body and unusual cellular activites. According to his process, diseases arise within an organism's individual cells,and can travel to other cells and destroy them. http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Rudolf_Virchow.html -
Pasteur disproves spontaneous generation by proving pasteurization
Before Louis Pasteur, it was widely believed that non-living things could produce living organisms. This is the idea of spontaneous generation, first proposed by Aristotle. Pasteur helped to disprove spontaneous generation, thus proving the third principle of the cell theory . His discoveries led him to create the theory of biogenesis, which states that all life comes from preexisting life. http://science.howstuffworks.com/dictionary/famous-scientists/chemists/louis-pasteur-info.htm -
Aristotle proposes the theory of spontaneous generation
Around 384 b.c. Aristotle proposed the theory of spontaneous generation as to say that all living things could come from non living things.
http://en.wikipedia.org/wiki/Spontaneous_generation
