Cells and Cell Theory Early Microscopes Robert Hooke built a microscope in 1665 He looked at cork from trees and saw tiny boxes. He called them cells. Hooke spent most of his time looking at plants and fungi. He thought that only plants had cells because they were easier to see. Anton van Leeuwenhoek •Van Leeuwenhoek built a microscope in 1673 •He examined pond scum and saw organisms •He named the “wee beasties” animalcules because they looked like little animals. •Today, we call these organisms protists. Finding Cells in Other Organisms Leeuwenhoek also examined blood. He noticed that the animal blood was different from human blood. He was the first person to view bacteria He discovered that the yeast that makes bread rise was a single-celled organism. CELL THEORY . . . 200 years later • In 1839, Schwann (who studied animals) and Schleiden wrote that • ALL organisms are made of one or more cells • The cell is the basic unit of life Virchow (1858) added • All cells come from existing cells Cell Similarities All cell have a membrane to keep the inside separate from the outside environment. All cells have cytoplasm (fluid) and small parts called organelles All cells have some hereditary material called Deoxyribonucleic Acid (DNA) Most cells are small in size. Why Are Cells Small? • Cells are small because if a cell’s volume gets too large, the cell’s surface area will not be able to take in enough nutrients or get rid of wastes fast enough to keep cells alive. • They need to keep a large surface area/volume ratio. TWO TYPES OF CELLS Prokaryotic Cells *Pro means NO nucleus These cells were the first type of cell on Earth. They are the smallest cells They have circular DNA and no membrane covered organelles These cells are found in organisms like bacteria. You have Eukaryotic Cells! Eukaryotic Cells *Eu mean true nucleus These cells are found in plants, animals, fungi, and protists. The cells are larger in size (10x) than prokaryotic cells They have a large, obvious nucleus and membrane covered organelles. They have DNA that is linear (in a line) and coiled up. What’s the Advantage of a Eukaryotic Cell? Different chemical reactions can happen at the same time Benefits of Being Multicellular •Larger Size •Multicellular organism are larger than unicellular organisms. They have less predators and more choice of prey. *Live Longer Multicellular organisms can loose cells and not die. Specialization Multicellular organisms can do more things . Cells can specialize to do different jobs. Multicellular organisms grow by producing more cells!