1. cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/

2. Where do living
things come from?
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/

3. Where do living
things come from?
What are they made
of?
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/

4. Where do living
things come from?
What are they made
of?
Answer - Cell Theory!
cc licensed flickr photo by Brian Hillegas: http://flickr.com/photos/seatbelt67/502255276/

5. Some old theories about the origin of life
cc licensed flickr photo by Bebulaki: http://flickr.com/photos/bebulaki/1457703975/

6. Tadpoles

7. Tadpoles
come from mud

8. Maggots
cc licensed flickr photo by Clintus McGintus: http://
flickr.com/photos/clintus/2523629054/
came from
rotting meat
cc licensed flickr photo by simplerich: http://flickr.com/photos/simplerich/
1393197323/

9. Spontaneous generation (abiogenesis):
a theory which explains that living
organisms can be spontaneously
created from non-living matter
Not an unreasonable explanation for
societies which didn’t have the right
technology to look at what living things
are made of.

10. The right technology
•Invented in Holland in 1590
•First cell seen/drawn by
Robert Hooke in mid 1600s.

11. 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”.

12. The first living cells were seen
by Antonie van Leeuwenhoek.

13. 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.

14. Experiment # 1 - Francesco Redi

15. Redi’s Experiment

16. Experiment # 2 - Lazzaro Spallanzani

17. Spallanzani’s Experiment
A
B

18. Spallanzani’s Experiment
Conclusion: Tiny
organisms from the air
A
caused growth in flask A.
These organisms could not
reach the broth in flask B.
B

19. Spallanzani’s Experiment

20. Spallanzani’s Experiment
Criticisms:

21. Spallanzani’s Experiment
Criticisms:
1: Spontaneous generation was believed to
require air to occur therefore it won’t
occur in a sealed container.

22. 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!

23. Louis Pasteur

25. • Boiled broth in a swan-necked flask.

26. • Boiled broth in a swan-necked flask.
• Dust from outside air could not get in
because of the long, bent neck of the flask.

27. • 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

29. Results:

30. Results:
•Broth remained clear, no bacteria found
when examined under microscope

31. Results:
•Broth remained clear, no bacteria found
when examined under microscope
•Dust collected in bend of swan neck

32. 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

33. cc licensed flickr photo by msitua: http://flickr.com/photos/
msitua/3246137819/

34. Cell Theory cc licensed flickr photo by msitua: http://flickr.com/photos/
msitua/3246137819/

35. Cell Theory cc licensed flickr photo by msitua: http://flickr.com/photos/
msitua/3246137819/
• Cells are the basic unit of life

36. Cell Theory cc licensed flickr photo by msitua: http://flickr.com/photos/
msitua/3246137819/
• Cells are the basic unit of life
• All cells come from pre-existing cells

37. Cell Theory cc licensed flickr photo by msitua: http://flickr.com/photos/
msitua/3246137819/
• Cells are the basic unit of life
• All cells come from pre-existing cells
• All living things are made of cells and cell
products