• All life is made of cells
• Discovered after microscope invented
• 1665: Robert Hooke first observed cork (dead plant bark)– Cork 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?
Cell Diversity
• Shape depends upon function• Nerve Shape: Elongated branching
– Function: Sends messages to and from brain• Red Blood Shape: Disc-like shape prevents clogging
– Function: Carries O2 throughout blood• Skin Shape: Flat & broad; layers overlap
– Function: Covers and protects the body
• 1) Prokaryote: Cells without a nucleus and other membrane-bound organelles– Oldest cells known (~4 billion years old)– Believed to have evolved first (oldest fossils)– AKA: Bacteria
• 2) Eukaryote: Cells with a nucleus & membrane bound organelles– More complex cells
– Evolved from prokaryotes
– Ex: Protists, Fungi, Plants, Animals
• Endosymbiosis Theory: Chloroplast & mitochondria were free-living organisms– Both were engulfed by a larger predator cell– Both gave the larger cell an advantage (make food and energy)– Predator cell provided each protection
• Over time, these cells could not survive without the mitochondria & chloroplast
• Evidence: Mitochondria & chloroplast contain own DNA, replicate, contain own ribosomes
QuickReview
• Cells shape is related to its job (function)
• Cells are the basic units of life
• Cells come from other cells