All life is made of cells Cells discovered after microscope invented 1665: Robert Hooke first observed cork (dead tree bark) –Boxes he saw reminded him of tiny rooms –He named the empty boxes “cells”

Three Parts: –1) All organisms are made of cells –2) The cell is the most basic unit of life –3) Cells come from other cells What’s the big problem with this theory? Where did the 1 st ever cell come from?

Cell Diversity Shape depends upon function ex: Nerve Shape: Elongated branching –Function: Sends messages to and from brain ex: Red Blood Shape: Disc-like shape prevents clogging –Function: Carries O2 throughout blood ex: Skin Shape: Flat & broad; layers overlap –Function: Covers and protects the body

1) Prokaryote: Cells without a nucleus and other membrane-bound organelles –First cells/life on Earth (oldest fossils = ~3.6 b.y.o) –AKA: Bacteria

2) Eukaryote: Cells with a nucleus & membrane bound organelles –More complex cells –Evolved from prokaryotes –Ex: Protists, Fungi, Plants, Animals

Prokaryotes vs. Eukaryotes

REview 1)Who first identified cells? 2)What was he/she examining? 3)Name the three parts to the cell theory. 4)Explain how the shape of a blood cell allows it to perform it’s job better. 5)Which category of cells contain nuclei? 6)Why are bacteria considered the oldest forms of life on Earth? 7)How do prokaryotes and eukaryotes differ?