How do we see cells Light Microscope: (aka optical microscope) uses visible light & system of lenses to magnify images of small samples Scanning microscope: (aka scanning electron microscope) uses electrons to produce high-resolution 3D images of specimens. Gets details 1000x smaller than light microscope

Cell Size Predict: How do you think an organism grows?

How Does an Organism Grow? By adding more cells! Cells Divide and divide, and divide, and divide

Limits to Cell Growth: #1 DNA Overload As cell size increases, it can’t keep up with the information needs of cell (DNA copies, making protein) AKA “information crisis” or overload Like a tiny library in a growing town

Limits to Cell Growth: #2 Surface Area Why does surface area matter? Lower surface area=easer it is to get things in & out of cells If cell is too large, useful substances (like water) can’t get to the center, waste products can’t get out

Surface area & Volume

How do cells avoid these problems? Cell Division: cells replicate themselves in two “daughter cells” the cell replicates, or copies, all of its DNA