This document summarizes several classic experiments that helped disprove the theory of spontaneous generation and establish the modern understanding of the evolution of life. It describes: 1) Redi's experiment in the 17th century, which showed that maggots come from fly eggs not spontaneous generation. 2) Needham's experiment claiming to show spontaneous generation could occur, but was disproven by Spallanzani's repetition using better controls. 3) Pasteur's famous experiment in the 19th century, using flasks with long curved necks, which conclusively showed no airborne vital factor was needed and life only arises from pre-existing life. These experiments helped establish that all life arises from pre

1. CLASSIC EXPERIMENTS ON
THE EVOLUTION OF LIFE

2. Previous Lesson:
Historical Development of the Concept
of Life
• Life started billions of years ago (few million years after the formation
of the planet)
• Life started as very simple form under the harsh condition of the
planet. (Prokaryotes)
• As the Earth changed, so did the organisms.
• Evolution took place until the simple organisms became more and
more complex.

3. THE THEORY OF SPONTANEOUS GENERATION
• States that vital forces or organic matter can create organisms from
inanimate objects
ARISTOTLE - claimed that some cases of organisms generate
spontanously
ROBERT HOOKE - an English Scientist who wrote the book
“ Micrographia” (1665) illustrated small organisms such as fruiting
struscture of molds. His illustration and descriptions of small
organisms became the first description of microorganisms.
ANTON VAN LEEUWENHOEK - the first person to see bacteria, a
Dutch scientist; he further developed simple microscope to
investigate the natural substances present in microbes. He discovered
bacteria studying a pepper-water infusion and called this organisms
as “ wee animalcules”

4. REDI’S EXPERIMENT
FRANCISCO REDI - an
italian scientist, designed a
scientific experiment to
demonstrate that maggots
do not just appear
spontaneously but are
produced from the eggs of
flies.

5. NEEDHAM’S TEST
JOHN TURBERVILLE NEEDHAM - English Biologist who
attempted to test the relevance of Redi’s experiment and
to prove the spontaneous generation can occur under the
right conditions.
During that time, it was believed that heat could kill even
the tiniest of organism.

6. • Heat could kill organisms even the smallest ones.
• When the broth was boiled, all organisms in ithad
died from the heat.
• Days later, he noticed that a thick solution had formed
on the broth.

7. SPALLANZANI’S EXPERIMENT
Lazzaro Spallanzani - Italian who sought to verify
Needham’s test in 1767. Spallanzani believed that
Needham had not heated broth enough to kill the
organisms in it.

8. • The set-up that was sealed remained free from
microbial growth.
• He concluded that life occurred from something that
entered the unsealed flask and that it was the one
responsible for life to grow.
• pag walang takip may pumasok sa loob na naggrow
kaya nagkaroon ng micribial growth.

9. PASTEUR’S TEST
LOUIS PASTEUR - opposed the concept of
spontaneous generation. He believed that
microorganisms present in putrefying materials
are present in the air or might have been
present on the surface where decaying
materials are present.
- his experiment convinced most scientist that
spontaneous generation could not occur.
STERILIZATION - process of heating was used by Pasteur
to eliminate contaminants.
Pasteur’s experiment gave rise to the study of
Microbiology. Later on, sterilization was developed and
carried out as basic procedure on both basic and
applied microbiology research.

10. • Pasteur made an experiment to test the idea that a
vital element from air was necessary for life to emerge.
• He boiled sugar solution with the yeast in flasks with
long neck.
• Through heating, he eliminated the contaminants.
• The flask was left open to allow the vital factor in the
air to enter but no organisms developed in the
mixture.
• It was because the microorganism settled only on the
bottom of the curved neck of the flask and could not
reach the mixture.

11. • Spontaneous Generation
• Scientist conducted experiments to prove or disprove
the idea of spontaneous generation.
• Francisco Redi - “Maggot in the Flask”
• John Needham - “Boiled broth to kill organisms in it.
Kept the container open”
• Lazzaro Spallanzani - “Redo John Needham’s
experiment but with a different set-up”
• Louis Pasteur - “Curved neck set-up”

12. 11 - ORIOLE
MYCA ILUSTRISIMO
MARIA ANGELA HERMOSO
LEIAN SINAD
SHEELA MAE RETAMAL
PRINCESS PEARL GARCIA