The Origin of Life 350 BC Aristotle Greek He was a philosopher He can about his ideas by thinking not experimenting Life arose from non living matter by spontaneous generation 1600 AD Van ID: 636121
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Slide1
Spontaneous generation
Proving and disproving
The Origin of LifeSlide2
350 BC Aristotle Greek
He was a philosopher. He can about his ideas by thinking not experimenting.
Life arose from non living matter by
spontaneous generationSlide3
1600 AD Van
Helmot
German
Published the recipe for the spontaneous generation of mice.
Place old rags in the corner of your attic.
Sprinkle it with bread crumbs and seeds
Voila (Hier) baby miceSlide4
1665 Robert Hooke English
Coined the word “Cells” by looking at a cork through a microscope.
He thought they looked like the little rooms or Cells that monks lived in.Slide5
1668 Francesco
Redi
Italian
Casts doubt on spontaneous generation
by discovering the life cycle of the fly.
They didn’t know that maggots were
Fly larvae.Slide6
1675 Anton van Leeuwenhoek Dutch
Discovers microorganisms “
animacules
”
With the first microscope.
Draws bacteria.Slide7
1748 John Needham Scottish
Supports spontaneous generation of organisms
Boiled broth 1 min.
Sealed with loose cork
Bacteria still grew
Therefore Spontaneous
generation must be trueSlide8
1776
Lazaro
Spallanzani Italian
Rejects Needham’s experiment. He said it was a bad procedure.
He redid the experiment.
Boiled the broth for 20 min.
Sealed flasks with glass tightly
No micro organisms appeared.
Therefore Spontaneous generation does
not
occur.Slide9
1820
Ignaz
Semmelweis
Austrian
Discovered that washing hands in hospital
Prevents infections and
Saves lives.
People didn’t believe himSlide10
The Cell Theory
The next 4 scientists each made discoveries about cells.
Together they create what we now call the cell theory.Slide11
1835
Félix
Dujardin French
Microorganisms are, in fact,
CellsSlide12
1838
Schleiden
&
Schwan German
1.Matthias
Schleiden
discovered
All Plants are made of
Cells
2.Theodor Schwann discovered
All Animals
are made of
cellsSlide13
1858 Rudolf Virchow German
All cells
come from other cellsSlide14
1861 Louis Pasteur French
Rejects spontaneous generation ,
Once and for all.
Discovers that microorganisms cause disease.Slide15
Pasteur’s experiment
Boil broth for 20 min.
Make a swan neck tube.
If bacterial growth comes from dust in the air,
then the dust will get trapped in the s bend and
contamination will not occur.
If bacterial growth is spontaneous but need a
“factor” from the air circulating,
then
contanination
will occur.
5. 150 years later there is still no contamination.
Spontaneous generation does not exist
6. When the tube broke or the liquid touched the neck,
Then the broth became contaminated immediately.Slide16
1862 Sad News
Semmelweis
dies of an infectionSlide17
1870 Thomas Henry Huxley English
Theory of “Biogenesis”
All life comes from life
Can any of you see a problem with this theory?
What question comes to mind?Slide18
1928 Alexander Flemming
English
Mold inhibits bacterial growth
Penicillin stops diseases.
And the
discoveries continue......Slide19
Modern Cell Theory
All
known living things are made up of cells.
The cell is structural & functional unit of all living things.
All cells come from pre-existing cells by division. (Spontaneous Generation does not occur).
Cells contains hereditary information which is passed from cell to cell during cell division.
All cells are basically the same in chemical composition.All energy flow (metabolism & biochemistry) of life occurs within cells.Slide20
A Timeline
1595
– Jansen credited with 1st compound microscope
1655
– Hooke described ‘cells’ in cork.
1674 – Leeuwenhoek discovered protozoa. He saw bacteria some 9 years later.1833 – Brown descibed
the cell nucleus in cells of the orchid.
1838
– Schleiden and Schwann proposed cell theory.
1840
– Albrecht von
Roelliker
realized that sperm cells and egg cells are also cells.
1856
– N.
Pringsheim
observed how a sperm cell penetrated an egg cell.
1858
– Rudolf Virchow (physician, pathologist and anthropologist) expounds his famous conclusion:
omnis
cellula
e
cellula
, that is cells develop only from existing cells [cells come from preexisting cells]
1857 –
Kolliker described mitochondria.1879 – Flemming described chromosome behavior during mitosis.Slide21
1883
– Germ cells are haploid, chromosome theory of heredity.
1898
– Golgi described the
golgi
apparatus.
1938 – Behrens used differential centrifugation to separate nuclei from cytoplasm.1939 – Siemens produced the first commercial transmission electron microscope.1952 – Gey
and coworkers established a continuous human cell line.
1955
– Eagle systematically defined the nutritional needs of animal cells in culture.
1957
– Meselson, Stahl and
Vinograd
developed density gradient centrifugation in cesium chloride solutions for separating nucleic acids.
1965
– Ham introduced a defined serum-free medium. Cambridge Instruments produced the first commercial scanning electron microscope.
1976
– Sato and colleagues publish papers showing that different cell lines require different mixtures of hormones and growth factors in serum-free media.
1981
– Transgenic mice and fruit flies are produced. Mouse embryonic stem cell line established.
1995
–
Tsien
identifies mutant of GFP with enhanced spectral properties
1998
– Mice are cloned from somatic cells.
1999
– Hamilton and Baulcombe discover siRNA as part of post-transcriptional gene silencing (PTGS) in plants