cell theory sept 2010
TRANSCRIPT
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/
Where do living things come from?
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/
Where do living things come from?
What are they made of?
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/
Where do living things come from?
What are they made of?
Answer - Cell Theory!
Some old theories about the origin of life
cc licensed flickr photo by Bebulaki: http://flickr.com/photos/bebulaki/1457703975/
Tadpoles
Tadpoles
come from mud
cc licensed flickr photo by Clintus McGintus: http://flickr.com/photos/clintus/2523629054/
Maggots
came from rotting meat
cc licensed flickr photo by simplerich: http://flickr.com/photos/simplerich/1393197323/
Spontaneous generation (abiogenesis):
a theory which explains that living organisms can be spontaneously created from non-living matter
Not an unreasonable explanation forsocieties which didn’t have the righttechnology to look at what living thingsare made of.
The right technology
•Invented in Holland in 1590•First cell seen/drawn by Robert Hooke in mid 1600s.
Looked at cork bark (made of dead cells). The small, empty spaces that he saw reminded him of a small room. He called them “cells”.
The first living cells were seen by Antonie van Leeuwenhoek.
The discovery of cells was one development that led to the end of spontaneous generation as a viable theory. Experimental evidence also showed the weakness of spontaneous generation.
Experiment # 1 - Francesco Redi
Redi’s Experiment
Experiment # 2 - Lazzaro Spallanzani
Spallanzani’s Experiment
A
B
Spallanzani’s Experiment
Conclusion: Tiny organisms from the air caused growth in flask A. These organisms could not reach the broth in flask B.
A
B
Spallanzani’s Experiment
Spallanzani’s Experiment
Criticisms:
Spallanzani’s Experiment
Criticisms:
1: Spontaneous generation was believed to require air to occur therefore it won’t occur in a sealed container.
Spallanzani’s Experiment
Criticisms:
1: Spontaneous generation was believed to require air to occur therefore it won’t occur in a sealed container.
2: Didn’t offer any explanation about where the bacteria did come from!
Louis Pasteur
•Boiled broth in a swan-necked flask.
•Boiled broth in a swan-necked flask.•Dust from outside air could not get in
because of the long, bent neck of the flask.
•Boiled broth in a swan-necked flask.•Dust from outside air could not get in
because of the long, bent neck of the flask.•Left for a few days
Results:
Results:
•Broth remained clear, no bacteria found when examined under microscope
Results:
•Broth remained clear, no bacteria found when examined under microscope
•Dust collected in bend of swan neck
Results:
•Broth remained clear, no bacteria found when examined under microscope
•Dust collected in bend of swan neck•If flask was broken or tipped so the broth
touched the dust, the broth would go cloudy after a couple of days
cc licensed flickr photo by msitua: http://flickr.com/photos/msitua/3246137819/
cc licensed flickr photo by msitua: http://flickr.com/photos/msitua/3246137819/Cell Theory
cc licensed flickr photo by msitua: http://flickr.com/photos/msitua/3246137819/Cell Theory
•Cells are the basic unit of life
cc licensed flickr photo by msitua: http://flickr.com/photos/msitua/3246137819/Cell Theory
•Cells are the basic unit of life •All cells come from pre-existing cells
cc licensed flickr photo by msitua: http://flickr.com/photos/msitua/3246137819/Cell Theory
•Cells are the basic unit of life •All cells come from pre-existing cells•All living things are made of cells and cell
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