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Biology 20 – Introduction Notes
What is Biology?
 Biology = _______________ (Bio = _____ - logy = ___________)
 What is life? While philosophers spend a lifetime pondering this
question, biologists give life a fairly practical definition:
 Life is defined by the following characteristics:
– ___________________________________________
– ___________________________________________
– ___________________________________________
– ___________________________________________
– ___________________________________________
Biology is the Most Interdisciplinary Science
 Because organisms are made of chemicals
 And chemicals are governed by the laws of physics
 And physics uses mathematics to describe natural phenomena
 And mathematics is the most useful tool in the world
 Biologists must master chemistry, physics, and mathematics to
master biology
Branches of Biology
– Molecular Biology – ______________________________
– Cellular Biology – ______________________________
– Botany – ______________________________
– Zoology – ______________________________
– Paleontology – ______________________________
– Ecology – __________________________________________
Why study biology?
So you can make decisions on some sensitive questions in society
such as:
If I choose to limit my family size, what methods of birth control do
I use?
Is it right to protect an endangered species at the expense of jobs?
Is it ethical to use fetal tissue in biomedical research?
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Biology 20 – Introduction Notes
Are there dangers in cloning humans?
Are genetically modified foods safe to eat?
Origins of Life (Pgs. 585-588)
Aristotle (384 –322 BC)
 Proposed the theory of ____________________________
 Also called ________________________________
 Idea that _______________ can arise from __________________
 Idea lasted almost 2000 years
Spontaneous Generation
 For centuries, people based their beliefs on their interpretations of
what they saw going on in the world around them without testing
their ideas
 They didn’t use the _____________________ to arrive at answers
to their questions
 Their conclusions were based on ___________________________
Francesco Redi (1668)
 In 1668, Francesco Redi, an Italian physician, did an experiment
with flies and wide-mouth jars containing meat.
 It was a common belief at the time that rotting meat turned into
maggots and flies.
Redi’s Experiment
 Redi used ____________________________________________.
 His hypothesis was that _________________________________.
 He observed these flasks to see in which one(s) maggots would
develop.
Redi’s (1626-1697) Experiments
Evidence against spontaneous generation:
1. Unsealed – ___________________________
2. Sealed – _____________________________
3. Gauze – _____________________________
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Biology 20 – Introduction Notes
Results of Redi’s Experiments
 The results of this experiment disproved the idea of spontaneous
generation for larger organisms, but people still thought
microscopic organisms like algae or bacteria could arise that way.
 He proved that only flies could give rise to more flies.
So how was the theory of abiogenesis disproved for microbes??
 Enter a famous scientist who developed a process for purifying
milk, etc.
 Who is he??__________________________ (1822-1895)
_______________ Problem
 Hypothesis: Microbes come from cells of organisms on dust
particles in the air; not the air itself.
 ________________ put broth into several special _____________
 Each flask was boiled and placed at various locations
____________________Experiment - Step 1
 S-shaped flask filled with broth
 The special shaped was intended to trap any dust particles
containing bacteria
___________________Experiment - Step 2
 _______________________
 _______________________
____________________ Experiment - Step 3
 Flask left at __________________________
 _____________________________________________
 Notice the dust that collected in the neck of the flask
______________Experimental Results
The Theory of __________________________
 _____________ S-shaped flask kept _______________________.
 Proved microbes only come from other microbes (life from life) biogenesis
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Biology 20 – Introduction Notes
What is a Theory??
 In science, a theory is a proposed description, explanation, or
model of the manner of interaction of a set of natural phenomena,
capable of predicting future occurrences or observations of the
same kind, and capable of being tested through experiment.

It follows from this that for scientists "theory" and "fact" do not
necessarily stand in opposition. For example, it is a fact that an
apple dropped on earth has been observed to fall towards the
center of the planet, and the theory which explains why the apple
behaves so is the current theory of gravitation.
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