1. There are two main types of cells; Prokaryotes and Eukaryotes Prokaryotic Cells Prokaryotic cells are the oldest forms of life and evolved 3.5 billion years ago. They are smaller and less complex than eukaryotic cells

2. Lack membrane-bound organelles: organelles enclosed in a membrane inside the cytoplasm – Their DNA is not contained inside of a nuclear membrane Prokaryotic organisms: – are unicellular – include common bacteria and bacteria-like cells (archaea) found in extreme environments

3. Eukaryotic Cells Eukaryotic cells evolved 2 billion years after prokaryotic cells They are larger and more complex than prokaryotic cells. They have membrane bound organelles inside of the plasma membrane – Their DNA is contained in a nuclear membrane

4. Eukaryotic Organisms: – Can be unicellular or multicellular Unicellular organisms: a single cell carries out of all life’s functions Multicellular organisms: have several specialized cells that work together to carry out all of life’s functions – Include plants, animals, protists, and fungi. http://learn.genetics.utah.edu/content/begin/cells/scale/