What is Science?
• This picture is of
a wood ant and a
microchip.
Thinking like a scientist
• While the picture
was colored in, it
shows the size of
each organism.
It’s not as hard as it looks…
What is Science?
The goal of science is to:
• investigate and understand the natural
world.
• explain events in the natural world.
• use those explanations to make useful
predictions.
What is Science?
• Science is an
organized way of
using evidence
to learn about
the natural world.
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So How do Scientists Work?
• Question:
Have you ever noticed what happens
to food left in an open trash can for a
few days in the heat?
How Scientists Work
• For centuries, people have watched these
worm-like maggots appear on discarded
food.
• The maggots seemed to appear out of
nowhere.
• This made people ask the question:
– Where do they come from?
How Scientists Work
• In Aristotle’s time
(about 2300 years
ago), people
believed that living
things were brought
into being from
nonliving things.
How Scientists Work
• They believed some special “vital” forces
gave some nonliving things the opportunity
to be alive.
• Example: Recipe for Bees
– Romans thought that you could create bees
by
1) killing a bull in winter
2) building a shed and putting the bull
inside with branches and herbs until the
summer
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How do living things come into
being?
• For centuries, people believed the
explanation that living things “arose”
from nonliving things.
• The maggots arose from meat, the
mice arose from grain and the beetles
arose from cow dung.
Is spontaneous generation the
answer?
• Francesco Redi
(1600’s)
– An Italian physician
– In 1668, he proposed a
different idea to explain
the appearance of
maggots on meat.
How do living things come into
being?
• The scholars of the time named
the idea of life arising from
nonliving matter spontaneous
generation.
Redi’s Experiment
• Redi placed meat in
four jars.
• He covered two jars
with gauze and left the
other two jars
uncovered.
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Redi’s Experiment
• Redi believed that the flies were
laying eggs that were too small to see
on the meat.
• After a few days, the eggs hatched
and maggots would appear on the
meat.
• He thought that the covered meat
would not have any maggots.
Redi’s conclusion
• Redi’s experiment confirmed what he
thought would happen.
• His tests showed that the maggots were
produced by flies.
• They also showed that spontaneous
generation was not possible.
Redi’s results
• Uncovered flask = maggots and flies
• Covered flask = no maggots
Another scientist tests Francesco
Redi’s findings…
• Lazzaro Spallanzani
(1700’s)
– Another Italian scholar
– Read about Redi’s
experiment and decided to
try to get the same results
from gravy.
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Spallanzani’s Experiment
• Spallanzani boiled two
containers of gravy.
• Why do you think he
boiled the gravy?
Spallanzani’s Experiment
• He sealed one jar
immediately and
left the other jar
open.
• After a few days, he
checked the jars.
Spallanzani’s results
The gravy in the open flask
was filled with microorganisms
(tiny living things).
The gravy in the sealed flask
did not have any
microorganisms.
Spallanzani’s conclusion
• Spallanzani concluded that
nonliving gravy did not produce
living things.
• He concluded that the
microorganisms in the unsealed
jar were the offspring of
microorganisms that had entered
the jar through the air.
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Another scientist tests spontaneous
generation…
• Louis Pasteur
(1864)
– A French scientist
– Finally found a way
to totally disprove
the idea of
spontaneous
generation
Pasteur’s Experiment
• Pasteur placed broth in two flasks.
• He boiled the flasks to kill any
microorganisms they might contain.
• He waited for one entire year to see if any
microorganisms were found in the flasks.
He did not see any microorganisms in
either flask.
Pasteur’s Experiment
• Pasteur designed a flask that had a long,
curved neck.
• The flask would be open to air, but
microorganisms from the air did not make
their way through the neck into the flask.
Pasteur’s Experiment
• One year after starting his
experiment, Pasteur broke the neck
of one of the flasks, allowing dust and
air and other particles to enter the
broth.
• What do you think his results were?
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Pasteur’s results
Pasteur’s conclusion
• In just one day, the flask was clouded from
the growth of microorganisms.
• His work concluded that all living things
come from other living things.
• His work also caused a major shift in the
way scientists viewed living things.
Reflection Frames:
• Today’s Topic:________________
1.
What did I learn about the topic?
2. What part of the topic made me “think?”
3. What did I enjoy about the topic?
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