Biology 1201A Lecture Notes - Carl Linnaeus, Kinetic Theory Of Gases, Karl Popper

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11 Nov 2011
Department
What is a Theory?
How did cheetahs evolve to run fast?
they had to chase after their prey
faster cheetahs survived and produced more offspring
they moved from a high density forest to flat lands and had to
run faster
they had to compete with bigger and stronger animals for their
prey
Common vernacular: an untested idea or opinion; speculation
Scientific Definition: an explanation of a set of natural phenomena,
based upon proven or testable hypotheses and observations; theory
tries to explain what we observe in nature based on testable concepts
Examples:
Theory of Continental Drift – Pangaea
Kinetic Molecular Theory
Theory of Relativity
The Big Bang Theory
Theory of Panspermia
Verifiability – true verification would require a positive result in every
instance; has to be good, testable, and tests must be able to prove
theory wrong (theory you can’t prove wrong isn’t as strongly
supported by evidence)
Fallibility – “only when a theory could be wrong is it impressive that it
survives testing and criticism” Karl Popper
Is the following statement (i) verifiable and (ii) falsifiable?
All swans are white.
i. Not Verifiable – you’d have to gather ALL swans to check
ii. Is Falsifiable – find ONE instance where the statement is false
Historical Development of Evolutionary Thought
Early Evolutionary Thought
Static classification and characterization
All creatures on Earth created once (by Earth of divine being)
and remain the same; unchanging
Aristotle – the Scala natura (384-322BCE)
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Argued that all species were fixed; once placed on
ladder they didn’t change/move
Argued that you could rank all organisms on a ladder of
intellect (increasing complexity)
Natural Theology (1700s)
Tried to understand God’s purpose for humans by
studying classification of objects (merged Aristotle with
story of how life was created in Genesis)
Carl von Linne- the Linnean system (1707-78)
Tried to classify species on Scale of Natura to
understand God’s purpose
Recognized as father of taxonomy
“Deus creavit, Linnean dispousit” – God creates, Linne
arranges
It’s time for a change
Le Comte du Buffon (1707-88)
Discovered vestigial traits –things that don’t have any
apparent function for the organism based on its
environment
Suggested that populations of species change over
time, not actual species (stuck to static classification)
Erasmus Darwin (1731-1802)
Suggested same as le Comte du Buffon
Thought all organisms were created by one cause and
then because of sensations, volitions, irritations, they
were able to change, acquire new parts, and pass those
on
No mechanism for evolution
Lamarckian evolution
Jean-Baptiste Lamarck (1744-1829)
Species evolve to better fit their environment
HOW?
Orthogenesis – “perfecting principle” all organisms are
trying to be best suited to environment (primitive
more complex) directional, decided, gradual change in
organism to become more complex, perfect
Principle of use and disuse
Inheritance of acquired characteristics
Transformational theory of evolution
11-10-19
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