1. Cell Theory

2. A long time ago… DNA was a relatively “new” discovery because it’s shape has only been around around 60 years But, what in the world did biologists study before that?? Cells – the smallest unit of life found in biology

3. Just how long ago? In 1665 (351 years ago!) … Robert Hooke found cells Robert Hooke – using a compound light microscope (like the ones we used in class) looked at cork and saw cells. He published drawings of cells (cork and fleas) in his book, Micrographia

4. Then, a few years later… In 1683 (332 years ago) Anton van Leeuwenhoek discovered one celled animal like organisms He called these protozoans and we still do today

5. How did they see this? Microscopes! Microscopes see things not visible to the naked eye. They see things we can’t see without their help. There are 2 main types: 1. Compound Light Microscope 2. Electron Microscope

6. The Cell Theory Cell Theory – one of the basics of biology which states the following things: A. All living things are made of cells B. Cells provide the basic structure and function of all living things C. Cells come from previously existing cells

7. Two different types of cells are in biology Prokaryotic – Basic cells without a nucleus or membrane-bound organelles They do have DNA, membranes, flagella and ribosomes, but nothing else

8. Two different types of cells in biology Eukaryotic Cells – true cells which have a nucleus and other membrane bound organelles These have DNA, a nucleus, ribosomes, mitochondria, ER, and so on, and on….

9. What are organelles? Organelles – the name for the smaller parts of a cell It includes nucleus, mitochondria, ribosomes, nucleolus, smooth Endoplasmic reticulum, rough endoplasmic reticulum, Golgi bodies, and so on

10. Cell Membrane It also includes a cell membrane Cell Membrane – the outside part of the cell which contains the organelles. It is a protective part of the cell to let things in and out. We’ll study this more in a couple of weeks!

11. How did this happen? The first cells were probably prokaryotic cells Endosymbiotic Theory – states that a prokaryotic cell lived inside another one in a symbiotic relationship (remember they need one another) This gives rise to a eukaryotic cell over time