In the s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells. By the late s, 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. Rudolf Virchow later made important contributions to this theory. Today, these tenets are fundamental to our understanding of life on earth. However, modern cell theory grew out of the collective work of many scientists.
Figure 1. Robert Hooke — was the first to describe cells based upon his microscopic observations of cork. This illustration was published in his work Micrographia. At the time, Hooke was not aware that the cork cells were long dead and, therefore, lacked the internal structures found within living cells.
Nearly years later, in , Matthias Schleiden — , a German botanist who made extensive microscopic observations of plant tissues, described them as being composed of cells. Visualizing plant cells was relatively easy because plant cells are clearly separated by their thick cell walls. Schleiden believed that cells formed through crystallization, rather than cell division. Theodor Schwann — , a noted German physiologist, made similar microscopic observations of animal tissue. In , after a conversation with Schleiden, Schwann realized that similarities existed between plant and animal tissues.
This laid the foundation for the idea that cells are the fundamental components of plants and animals. In the s, two Polish scientists living in Germany pushed this idea further, culminating in what we recognize today as the modern cell theory. In , Robert Remak — , a prominent neurologist and embryologist, published convincing evidence that cells are derived from other cells as a result of cell division. However, this idea was questioned by many in the scientific community.
See the following Eye on Ethics feature for more about this controversy. He was also among the first to use animals in his research and, as a result of his work, he was the first to name numerous diseases and created many other medical terms.
Despite his significant scientific legacy, there is some controversy regarding this essay, in which Virchow proposed the central tenet of modern cell theory—that all cells arise from other cells. Robert Remak, a former colleague who worked in the same laboratory as Virchow at the University of Berlin, had published the same idea 3 years before.
However, in the nineteenth century, standards for academic integrity were much less clear. Today, the process of peer review and the ease of access to the scientific literature help discourage plagiarism.
Although scientists are still motivated to publish original ideas that advance scientific knowledge, those who would consider plagiarizing are well aware of the serious consequences.
In academia, plagiarism represents the theft of both individual thought and research—an offense that can destroy reputations and end careers. Figure 2. As scientists were making progress toward understanding the role of cells in plant and animal tissues, others were examining the structures within the cells themselves. In , Scottish botanist Robert Brown — was the first to describe observations of nuclei, which he observed in plant cells.
Then, in the early s, German botanist Andreas Schimper — was the first to describe the chloroplasts of plant cells, identifying their role in starch formation during photosynthesis and noting that they divided independent of the nucleus.
He proposed a similar origin for the nucleus of plant cells. This was the first articulation of the endosymbiotic hypothesis , and would explain how eukaryotic cells evolved from ancestral bacteria. Wallin published a series of papers in the s supporting the endosymbiotic hypothesis, including a publication co-authored with Mereschkowski. Wallin claimed he could culture mitochondria outside of their eukaryotic host cells.
What is the cell theory and who discovered it? Question 62bbb. What role did the invention of the microscope play in the development of the cell theory?
How long did it take scientists to develop the cell theory? What was Robert Hooke's contribution to the cell theory? See all questions in The Cell Theory. Impact of this question views around the world. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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Related Resources. Cell Biology. View Collection. History of the Cell: Discovering the Cell. View leveled Article. Unicellular vs. View Article. Animal Cell.
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