Cell Theory
Understanding of cells required
1.Improvement of microscopes
2.Hundreds of years of research and observations
The Cell Theory states
1.All living things are made of cells
2.Cells are the basic units of structure and function in living things
3.Cells come from pre-existing cells
Exceptions to cells theory
1. Where did the first cell come from?
2. Viruses: non-living genetic material; need to
act as parasites to reproduce
3. Mitochondria and chloroplasts have their own DNA; partially reproduce on their own
Cell Theory Timeline
1590s: Zacharias Janssen worked with his father and invented the first compound microscope 1665: Robert Hooke observes cork under a microscope and names the tiny boxes he saw
“cells”
1673: Anton von Leeuwenhoek observed single-celled organisms and blood cells
Cell Theory Timeline
1801: Robert Brown discovers the nucleus of the cell
1838: Matthias Schleiden (ShLY-dun) says all plants are made of cells
Theodor Schwann says all animals are made of cells 1855: Rudolph Virchow (FUR-koh)says cells only come from other cells
Cell scale
cell scale
Levels of organization
Cells: Smallest structural and functional unit of
an organism
E.g. Skin cells, Nerve cells
Tissues: a group of similar cells that perform
particular functions
E.g. Nerve, muscle, connective, epithelial
Organs: groups of tissues working together
E.g. Heart, Kidney
Organ systems: a group of organs working
together
E.g. Digestive system, nervous system
Basic Cell Structure
The cell membrane: A thin, flexible barrier
around the cell.
Cell wall: