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The Discovery of Cells Cells were not
described until 1665……….WHY?
1. Scientists did not begin to use microscopes until the mid-1600’s
2. Most cells are too small to see without the microscope!
The Discovery of CellsA. Robert Hooke (1665)
1. English Biologist
2. Observed a thin slice of cork (plant material) using an early microscope
3. Saw thousands of tiny chambers which he called “cells”
Draw what he saw in the box
The Discovery of Cells
B. Anton van Leeuwenhoek (1674)1. Dutch biologist2. Observed tiny living organisms in drops of pond water
through a simple microscope.
C. Matthias Schleiden (1838)1. German botanist concluded all plants are made of cells
D. Theodor Schwann (1839)1. German biologist stated all animals are made of cells
E. Rundolph Virchow (1855)1. Proposed all cells come from existing cells
Cell Theory
The discoveries of all of the mentioned biologists formed a fundamental concept
in biology known as CELL THEORY
1. All living things are composed of cells
2. Cells are the basic units of structure and function in living things
3. New cells are produced from existing cells
Cells have common characteristicsA. DNA
Genetic material
B. Cell Membrane Lipid bi-layer that controls what goes into and out
of the cell
C. Ribosomes Structures used in protein synthesis
D. Cytoplasm The interior of the cell
E. CytoskeletonFibers that give cells structure
Prokaryotic Cells “Pro” = before, “karyotic” = nucleus At least 3.5 billion years old Simplest and smallest cells No nucleus (Nucleiod region in the center to hold DNA)
No specialized organelles(Still function as living: grow, reproduce and respond to environment)
Examples: Bacteria and blue-green algae
Eukaryotic Cells
A. “Eu” = true, “karyotic” = nucleus
B. Evolved about 1.5 billion years ago
C. Larger and more complex than prokaryotes
D. Nucleus (DNA packaged in chromosomes)
E. Many specialized organelles
F. Examples: Plants, Animals, protist & fungi
Comparison ChartAll Cells Prokaryotes Eukaryotes
•Found in living
things•Basic unit of life•Produced from
existing cellsContain:
•Cell membrane•DNA•Ribosomes•Cytoplasm•Cytoskeleton
•Older•Smaller•Simple•No nucleus
Nucleoid region
•No specialized organelles•Examples: bacteria, algae
•Newer•Larger•Complex•Nucleus•Many specialized organelles
•Examples: plants, animals, protists, fungi