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Lecture 3

BIOLOGY 1M03 Lecture Notes - Lecture 3: Cell Theory, Spontaneous Generation, List Of First Overall Nba Draft Picks

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Dr. Dushoff

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Lecture 3
Cell Theory (Cont'd); Pasteur Experiment
Spontaneous generation may not have occurred
Maybe the broth wasn’t the right kind to support cells
Maybe the flask was somehow discouraging or poisonous
Does this prove all cells come from cells?
Maybe cells can generate spontaneously under other conditions
Maybe that's not what's happening here
Hypothesis: We pursiue by evaluating hypothesis (sing. Hypothesis) these are
proposed explanations of facts
We use hypothesis to make predictions, use experiments to falisfy hypotheses to prove
they are false
Most hypotheses cannot be proved to be true,instead if we fail to falsify them, we
say that they are supported
If a hypothesis explains many facts, and survives attempts at falsification, we tend
to believe it
Observational Studies: Look for ways to collect data that will support or challenge
Scientists are cautious about making conclusions from observational studies
Its hard to know if you’ve taken everything into account
Experiments are more reliable
But you cant always do experiments, which is why we do observational studies
Why are giraffes so tall?
They eat from trees, so that probably has something to do with it
They use their necks for dramatic fights so that probably has something to do with
What can you do to investigate?
o How high do the giraffes feed?
o Do males with long necks win fights?
Winners of the fights get the females; which is why they also have long necks?
4.2 Experiments
How do ants navigate landscapes? They find food and return to their nests; They
usually walk in the same line so they might be following a trail of smell to find their
Saharan desert ants meander long distances to find food, in a squiggly line, but
then walk home ina straight line
Maybe they have some quantitative sense by judging distance by counting steps
o After cutting ant legs or making them longer; they discovered that ants count
their steps to get home. With stumps, it didn't go far enough, with stilts, it went
too far
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