1. Spontaneous generation vs. biogenesis
How does life begin?
Spontaneous generation
vs. biogenesis

2. SPONTANEOUS GENERATION
In the early 1600’s,
some scientists believed that
life began spontaneously!

3. Recipe for Bees Kill a bull during the first thaw of winter.
Build a shed.
Place the dead bull on branches and herbs inside the shed.
Wait for summer. The decaying body of the bull will produce bees.

4. SPONTANEOUS GENERATION
Process by which life begins when “magical ethers” enter non-living things to make them alive
Examples: mice were thought to come from garbage piles, geese from the mud banks of the river, maggots from meat
In the 1600’s, scientists began challenging this idea.

5. Francesco Redi

6. Redi’s Experiment Set-up 3 jars with rotting meat Open top
Sealed with lid
Covered with cloth
Observations
Maggots
No maggots

7. Lazzaro Spallanzani

8. Spallanzani’s Experiment
Set-up
Nutrient broth heated
Flask left open
Flask sealed
Observations
Bacteria grew
No bacteria grew

9. Louis Pasteur

10. Pasteur’s Experiment Set-up Nutrient broth heated
Flask with curved neck
Flask with straight neck
Observations
No dust could reach broth, no bacteria grew
Dust settled, bacteria grew

11. EVIDENCE AGAINST SPONTANEOUS GENERATION
The experiments of Redi, Spallanzani, and Pasteur showed the life does not arise spontaneously
LIFE must come from LIFE
These experiments supported the theory of biogenesis

12. BIO= life GENESIS= the beginning
BIOGENESIS
BIO= life
GENESIS= the beginning

13. BIOGENESIS
Living things come from other living things. They do not arise spontaneously!

14. REFERENCES Biology: The Web of Life. Scott Foresman-Addision Wesley