StudyGuideBiology–The Biology of Cells1. Cells DefinedOne of the most important ideas in biology is thatall living things are made of cells. Cells are thesmallest units of life, and every organism depends on them to survive.Some living things are very simple and haveonly one cell. These are calledunicellular organisms.Other organisms, like plants and animals, are much more complex. They are made ofmany cellsthatwork together. In these organisms, similar cells formtissues, tissues combine to formorgans, andorgans work together asorgan systems.Even though these organisms may seem complicated, everything they do—growing, moving, andstaying alive—depends on what happens inside their cells. Cells are truly at the center of all life.1.1 The Discovery of CellsThe study of cells began with the invention of the microscope.In the mid-1600s, an English scientist namedRobert Hookelooked at a thin slice of cork using one ofthe first microscopes. What he saw surprised him. The cork was made up of many tiny, box-likespaces. These spaces reminded him of the small rooms in a monastery, which were calledcells.Because of this similarity, Hooke gave them the namecells—a name we still use today.Around the same time, a Dutch merchant namedAnton van Leeuwenhoekmade even moredetailed observations. Using powerful microscopes that he designed himself, he studiedplant cells,animal cells, and tiny living organisms. His work helped scientists realize that cells were not justfound in cork but were part of many forms of life.1.2 The Development of Cell TheoryAs scientists continued studying cells, they began to notice important patterns.In 1838, a German botanist namedMatthias Schleidenconcluded thatall plants aremade of cells.One year later, his colleagueTheodor Schwann, an anatomist, expanded this idea by stating thatallanimals are also made of cells.Preview Mode
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