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Spontaneous generation Proving and disproving Spontaneous generation Proving and disproving

Spontaneous generation Proving and disproving - PowerPoint Presentation

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Spontaneous generation Proving and disproving - PPT Presentation

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

cell cells generation spontaneous cells cell spontaneous generation theory life microscope occur broth discovered mice growth min german microorganisms experiment english bacteria

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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