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The Cell Theory History • 1838- Mattias Schleiden concluded that all plants are made of cells • 1839- Theodore Schwann determined that animals are made of cells • 1858-Rudolph Virchow discovered that all cells come from other cells Three Parts of the Cell Theory 1. All living things are made of one or more cells 2. Cells are the basic unit of structure and function in organisms 3. All cells arise from existing cells Cell Size •Small cells function more efficiently than large cells •Why? Small cells can exchange substances with their environment faster because small objects have a larger surface area to volume ratio than large objects Cell Types •Prokaryotes-(bacteria and archeabacteria)single celled organisms, lack a nucleus, little internal structure, simple and small, the only organisms on Earth for 2 billion years •Eukaryotes-(plants, animals, fungi, protists)organisms whose cells have a nucleus and internal structures, single celled and multicelled, evolved 2.5 billion years ago, large and complex Prokaryote and Eukaryote Comparison