CONTRIBUTIONS TO THE
CELL THEORY
Timeline of scientists and their
discoveries
1) Anton von Leeuwenhoek
1600’s
Dutch businessman
Invented 1st simple
light microscope
Anton von Leeuwenhoek (con’t)
Observed tiny
organisms in pond
water
Organisms were
nicknamed “wee
beasties”
2) ROBERT HOOKE
1665
English physicist
Observed flowers,
insects, and plant
tissue
ROBERT HOOKE (con’t)
Observed thin
slices of cork (oak
tree)
Coined the term
“cell” based on the
rooms in a
monastary
3) ROBERT BROWN
1833
Observed plant
cells under the
microscope
ROBERT BROWN (con’t)
Observed a dark
structure inside
each cell and coined
the term “nucleus”
4) MATTHIAS SCHLEIDEN
1838
German botanist:
scientist who
studies plants
Concluded all
plants are made up
of cells
5) THEODORE SCHWANN
1839
German biologist
Concluded all
animals are made
of cells
6) RUDOLF VIRCHOW
1855
German Physician
Studied cell
reproduction
Concluded all cells
arise from
preexisting cells
The cell theory
1. All living things are composed of
cells
2. Cells are the basic unit of structure
and function in living things.
3. All cells arise from preexisting cells.
Introduction to Cells
Chapter 6
Levels of Organization
All living organisms can be studied on
many levels
From smallest to largest they are:
Chemical (atoms & molecules)
Cells
Tissues
Organs
Organ Systems
Whole Organism
Basic Structure of Cells
All cells have a cell membrane and cytoplasm
Cell Membrane: thin, flexible barrier around cell
Composed of lipids and proteins
Cytoplasm: jelly-like material inside the cell
All cells contain organelles
Organelles: small structures that perform different
functions within a cell
Prokaryotic Cells
Do NOT have a nucleus
Instead a small ring of DNA is
free-floating in center of cell
Organelles do NOT have a
membrane
i.e.: bacteria (very simple
organisms)
Eukaryotic Cells
Contain a nucleus
Organelles are membrane-bound
Much more complex
i.e.: plants, animals, fungi