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Unit Two-1 Similarity & Diversity Among Living Things-Life Processes Cell Theory I believe it is difficult to understand Biology unless you Know where "Modern Biology" began. 3 Main Ideas about Cell Theory 1) The cell is the basic unit of structure and function 2) All cells come from pre-existing cells 3) Viruses are an exception to the cell theory Robert Hooke (1635-1703), one of the first scientists to use a microscope to examine pond water, cork and other things, referred to the cavities he saw in cork as "cells", Latin for chambers. Mattias Schleiden (in 1838) concluded all plant tissues consisted of cells. In 1839, Theodore Schwann came to a similar conclusion for animal tissues. Rudolf Virchow, in 1858, combined the two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory. Thus there is a chain-of-existence extending from your cells back to the earliest cells, over 3.5 billion years ago. The cell theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells. http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookintro.html#Other%20theories Human Physiology It is helpful to view and dissect other organisms to better understand human physiology. Today, due to technology, some very advanced virtual diisections are available. Please click on the link below to perform some dissections. |