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Chapter 3 Cells: The Basic Units of Life Organization of Life All living things have one or more cells Not all of our cells look the same Humans have over 2oo types of cells each specialized for different jobs Tissues A group of similar cells that work together to perform a specific job in the body Organ A combination of two or more tissues that work together to perform a special function in the body Organ System A group of organs that work together to perform body functions Organism Anything that can independently carry on life processes Unicellular vs. Multicellular Unicellular- organism made of one cell Multicellularorganism made of many cells Population A group of individuals of the same species that live together in the same area at the same time Community All of the populations of different species that live and interact in an area Ecosystem A community of organisms and their nonliving environment Robert Hooke English scientist 1665 cut a thin slice of cork and observed with a microscope Hooke saw small boxes resembling the small rooms monks live in cells Anton van Leeuwenhoek Dutch microscope maker 1675 first person to see living cells under the microscope 150 years later….. Matthias Schleiden (1838) German botanist Concluded that all plants are composed of cells Theodor Schwann (1839) German zoologist Concluded that all animals are composed of cells Rudolph Virchow 1858, German doctor Saw cells couldn’t develop from anything other than other cells Collectively known as the Cell Theory 1. 2. 3. All living things are composed of one or more cells Cells are organisms’ basic units of structure and function Cells come from existing cells