Transcript Document 7182795

Biology Warm Up: Copy these assignments into your binder. Be sure to include dates and page numbers
August 30-31
WarmUp:
Agenda
Lab: Using a Compound Microscope p29
Homework: Read and take complete notes 1.1 and 1.2
answer q1-5p15
DUE NEXT CLASS
September 1
WarmUp:
Hypothesis/Procedure/Observations
QuickLab: What are the Characteristics of Living Things?p18
Homework: Read and take notes 1.3 answer q1-6p22
DUE NEXT CLASS
September 2-3
WarmUp: Levels of Organization
InClass: Safety Contract
and quiz
InClass: Applying the Scientific Method p31LabManual
Quiz: sections 1.1 – 1.3
Homework: No homework over Labor Day Weekend!
When you finish, please read the procedure for the Compound Microscope lab on page
1
29. Write a summary for each step of the procedure.
Thinking Like a
Scientist
1.d. Think logically and use evidence
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Aristotle (384 –322 BC)
Proposed theory of spontaneous
generation
Also called abiogenesis
Living things can arise from
nonliving matter
Idea lasted almost 2000 years
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Examples of
Spontaneous
Generation
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Example #1
Observation: Every year in the
spring, the Nile River flooded
areas of Egypt along the river,
leaving behind nutrient-rich mud
that enabled the people to grow
that year’s crop of food.
However, along with the muddy
soil, large numbers of frogs
appeared that weren’t around in
drier times
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Example #1
Hypothesis: It was perfectly
obvious to people back then that
muddy soil gave rise to the frogs
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Example #2
Observation: In many parts of
Europe, medieval farmers stored
grain in barns with thatched
roofs (like Shakespeare’s house).
As a roof aged, it was not
uncommon for it to start leaking.
This could lead to spoiled or
moldy grain, and of course there
were lots of mice around.
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Example #2
Hypothesis: It was obvious to
them that the mice came from
the moldy grain.
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Example #3
Observation: Since there were no
refrigerators, the mandatory,
daily trip to the butcher shop,
especially in summer, meant
battling the flies around the
carcasses. Typically, carcasses
were “hung by their heels,” and
customers selected which chunk
the butcher would carve off for
them.
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Example #3
Hypothesis: Obviously, the rotting
meat that had been hanging in the
sun all day was the source of the
flies.
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Abiogenesis Recipes
Recipe for mice:
Place a dirty shirt or some rags in
an open pot or barrel containing a
few grains of wheat or some wheat
bran, and in 21 days, mice will
appear. There will be adult males
and females present, and they will
be
capable
of
mating
and
reproducing more mice.
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Testing a
Hypothesis:
The controlled
experiment.
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Francesco Redi
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Step 1 - Observation
There were flies around meat
carcasses at the Butcher
shop.
Where do the flies come
from?
Does rotting meat turn into
or produce rotting flies?
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Step 2 - Hypothesis
Rotten meat does not turn
into flies. Only flies can
make more flies.
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Redi’s (1626-1697) Experiments
Evidence against spontaneous generation:
1. Unsealed – maggots on meat
2. Sealed – no maggots on meat
3. Gauze – few maggots on gauze, none on meat
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Redi’s (1626-1697) Experiments
In a controlled experiment, the scientist changes
only one variable, the manipulated variable.
What is the manipulated variable in this experiment?
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Redi’s (1626-1697) Experiments
The variable the scientist, observes, measures,
and records is the responding variable.
What is the responding variable in this experiment?
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Redi’s (1626-1697) Experiments
It is called a controlled experiment because all
other variables are not allowed to change. Those
other variables are the controlled variables.
List several controlled variables for this experiment.
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Anton van Leeuwenhoek (1674)
Leeuwenhoek began making and looking
through simple microscopes
He often made a new microscope for each
specimen
He examined water and visualized tiny
animals, fungi, algae, and single celled
protozoa; “animalcules”
By end of 19th century, these organisms
were called microbes
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Anton van Leeuwenhoek 1632-1723
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Leeuwenhoek’s Microscope
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Needham’s Experiment
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Lazzaro Spallanzani’s (1765)
Boiled soups for almost an hour
and sealed containers by melting
the slender necks closed.
The soups remained clear.
Later, he broke the seals & the
soups became cloudy with
microbes.
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Spallanzani’s Results
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Conclusion
Critics said sealed vials did
not allow enough air for
organisms to survive and that
prolonged heating destroyed
“life force”
Therefore, spontaneous
generation remained the
theory of the time
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The Theory
Finally Changes
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How Do Microbes Arise?
By 1860, the debate had become so
heated that the Paris Academy of
Sciences offered a prize for any
experiments that would help resolve
this conflict
The prize was claimed in 1864 by
Louis Pasteur, as he published the
results of an experiment he did to
disproved spontaneous generation in
microscopic organisms
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Louis Pasteur (1822-1895)
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Pasteur's Problem
Hypothesis: Microbes come
from cells of organisms on dust
particles in the air; not the air
itself.
Pasteur put broth into several
special S-shaped flasks
Each flask was boiled and placed
at various locations
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Pasteur's Experiment - Step 1
S-shaped Flask
Filled with broth
The special shaped was
intended to trap any
dust particles
containing bacteria
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Pasteur's Experiment - Step 2
Flasks boiled
Microbes Killed
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Pasteur's Experiment - Step 3
Flask left at various
locations
Did not turn cloudy
Microbes not found
Notice the dust that
collected in the neck of
the flask
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Pasteur's Experimental Results
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The Theory of Biogenesis
Pasteur’s S-shaped flask kept microbes
out but let air in.
Proved microbes only come from other
microbes (life from life) - biogenesis
Figure 1.3
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