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Cell Theory In 1665, Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material. Cork looked like thousands of tiny, empty chambers. Hooke called these chambers “cells.” Discoveries leading to cell theory: 1665 – Robert Hooke saw and named cells 1838 – Matthias Schleiden concluded that all plants were made of cells 1839 – Theodor Schwann stated that all animals were made of cells 1855 – Rudolph Virchow concluded that new cells were created only from division of existing cells. Cell Theory • All living things are made of cells • Cells are the basic unit of structure and function of living things • Cells come from preexisting cells by reproduction All cells have: Cell membrane – controls what enters and leaves the cell DNA – genetic material 2 categories of cells: Prokaryotes Eukaryotes • No nucleus • No membrane bound organelles Ex: bacteria • Have a nucleus • Have membrane bound organelles Ex: Plants, Animals, Fungi, Protists Prokaryote Eukaryote 1. What are the 3 parts of cell theory? • All living things are made of cells • Cells are the basic unit of structure and function of living things • Cells come from preexisting cells by reproduction 2. What 2 things do all cells have? Cell membrane – controls what enters and leaves the cell DNA – genetic material 3. How do prokaryotes differ from eukaryotes? • Prokaryotes do not have a nucleus • Eukaryotes do have a nucleus.