Development of Cell Theory

ByDiana L. Duckworth

Rustburg High SchoolCampbell County

Key Actors (must know)

• Van Leeuwenhoek

• Hooke

• Brown

• Schleiden

• Schwann

• Virchow

• Pasteur

Compound Microscope

• Jansen (Holland) 1595– (more than one lens)

• Anton van Leeuwenhoek– Single lens monocular in

1660’s– Observed bacteria &

protozoa– Continued publishing for 50

years– After his death, no good

microscopes for century

http://www.clt.astate.edu/mhuss/toppage6.htm

Robert Hooke 1655

• Observed cells in cork• Actually just cell walls• Coined the word “cell”

http://www.clt.astate.edu/mhuss/toppage6.htm

Robert Brown 1833

• Discovery of Nucleus• An opaque spot in

cells of epidermis of orchids

• Soon observed in other cells

• Brownian motion – random motion of particleshttp://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html

Schleiden Schwann

http://kentsimmons.uwinnipeg.ca/cm1504/celltheory.htm

Cell Theory – First Statement

• Schleiden & Schwann – separately stated• “All living things are composed of living

cells.” 1838 -1839• Schleiden – detailed observation of

nucleus– Gave credit to Brown about nucleus(but not

Schwann about cell theory)– Most important part of cell– All other parts develop from nucleus– Still believed that cells arose spontaneously

Rudolph Virchow

• 1855 – “Omnis cellula e cellula”

• All living cells arise from pre-existing cells

• No spontaneous generation

http://kentsimmons.uwinnipeg.ca/cm1504/celltheory.htm

Louis Pasteur

• Experimentally disproved spontaneous generation

• Florence flask – open allowed bacteria to settle into sterile medium

• S-neck flask with cotton plug – no bacteria– Remove S-neck got

bacteria

http://kentsimmons.uwinnipeg.ca/cm1504/celltheory.htm

http://kentsimmons.uwinnipeg.ca/cm1504/celltheory.htm

Cell Theory – Main Tenents

• All life forms are made of one or more cells

• Cells only arise from pre-existing cells

• The cell is the smallest form of life

• 1880 – Weissman– Cells living today can trace their ancestry

back to ancient times – there must be a common ancestral cell