Cells and Life
Cells and Life. September 7, 2012. Objectives. I can summarize cell theory. I can identify the characteristics of life. Cells are the smallest unit of life. Most cells are so small you cannot see them without some type of magnifying device.
Cells and Life
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Cells and Life September 7, 2012
Objectives • I can summarize cell theory. • I can identify the characteristics of life.
Cells are the smallest unit of life. • Most cells are so small you cannot see them without some type of magnifying device. • For a very long time, people did not know that cells existed.
Seeing Cells! • Light Microscope (around 1600) • Magnifies 1,500 times original size. • 1665 Robert Hooke observes cells. • Cannot see all the structures of the cell.
Seeing Cells! • Electron Microscope (1930 s) • Able to see most structures inside the cell. • Magnifies 100,000 times original size! • Ruska and Knoll in Germany
Cell Theory • In the 1830 s German scientists Schleiden and Schwann found that plants are made of cells and animals are made of cells. • German scientists also proposed that cells come from preexisting cells.
Cell Theory • All organisms are made of one or more cells. • The cell is the smallest unit of life. • All new cells come from preexisting cells.
Characteristics of Life • Living things must exhibit all the characteristics of life: Organization, Responses, Growth and Development, Reproduction, Homeostasis, and Energy.
Reproduction • Re/produce “create again”
Homeostasis Homeo/stasis “stay the same” -Organisms work to keep the internal conditions within certain limits.