Transcript Toronto_UTACCEL_Evolution

UTACCEL 2010
Adventures in Biotechnology
Graham Cromar
Part 1: Evolution
Darwin’s Voyage 1831-1836
Adaptations of
finches to various
habitats is consistent
with descent (with
modification) from a
common ancestor.
Darwin’s four tenets
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Inheritance
Variability
Limited resources
Selection
Evolution
Note:
Evolution is not random!
Evolution has no goal or predetermined direction
Lines of Evidence
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Fossil record
Selective breeding
Ontology
Comparative anatomy
Direct observation
Comparative genomics
Ontology describes the origin and the development of an organism from the
fertilized egg to its mature form
Fossil Record provides many
intermediate forms
Human Lineage
Selective breeding
Selective breeding has produced this impressive range of characteristics in only a
few hundred years. Note these animals are technically still the same species. Both
are descended from wolves.
Comparative anatomy
Vestigial structures, such as
pelvic bones in the baleen
whale, are evidence of
evolution because they show
structural change over time.
Phylogenetic Tree of Life
Hillis Plot
This phylogenetic tree, created by David Hillis, Derreck Zwickil and
Robin Gutell, depicts the evolutionary relationships of about 3,000
species throughout the Tree of Life. Less than 1 percent of known
species are depicted.
Species Diversity
Animals: estimated 3-30 million species
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|--Invertebrates: 97% of all known species
| `--+--Sponges: 10,000 species
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|--Cnidarians: 8,000-9,000 species
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|--Molluscs: 100,000 species
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|--Platyhelminths: 13,000 species
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|--Nematodes: 20,000+ species
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|--Annelida: 12,000 species
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`--Arthropods
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`--+--Crustaceans: 40,000 species
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|--Insects: 1-30 million+ species
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`--Arachnids: 75,500 species
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`--Vertebrates: 3% of all known species
`--+--Reptiles: 7,984 species
|--Amphibians: 5,400 species
|--Birds: 9,000-10,000 species
|--Mammals: 4,475-5,000 species
`--Ray-Finned Fishes: 23,500 species
We humans have an over-inflated
opinion of our own importance.
In fact, we are only one of millions
of species.
Even our close kin the vertebrates
are not as successful in biological
terms as the invertebrates in
terms of diversity and biomass.
Its still a microbial world: There are
over a billion viruses in a teaspoon of
sea water.
There are about 100 trillion cells in
the human body and over ten times
that many bacteria in our guts.
Evolutionary Arms Race
Happens also on a molecular scale
Our immune systems are locked in an arms race with infections and rapidly
develop defences against their invaders, research suggests
Introduction to Game
Theory
The Prisoners’ Dilemma provides insight into
the difficulty in maintaining cooperation.
Often people fail to cooperate with one
another even when cooperation would make
them better off. This applies equally to
animals whose behaviour is determined by
instinct.
The prisoners’ dilemma is a particular
“game” between two captured prisoners that
illustrate why cooperation is difficult to
maintain even when it is mutually beneficial.
*2
Suppose there are 2 criminals- Mike
and Alex.
The police have caught them on a
weapons’ charge which the
punishment is 1 year.
The police suspect they robbed a bank,
but lack of evidence, therefore, they
need one or both of them to confess.
They separate the criminals and offer
each of them the same deal:
*3
• If you confess to the bank
robbery. I’ll let you go free and
your partner will get 20 years
in jail.
• If you both confess, we won’t
have to go to trial so you will
each get 8 years in jail.
• If neither of you says anything,
we’ve got you on the weapons’
charge, so you will each get
1year in jail.
*4
Payoff Matrix
Alex’s Decision
Mike’s
Decision
Stay Silent
Confess
Stay Silent
-1\-1
-20 \ 0
Confess
0 \ -20
-8\-8
• If Alex choose to confess, Mike will confess too, for -8 > -20.
• If Ales choose to keep silent, Mike will confess anyways, for 0 > -1.
• If Mike choose to confess, Alex will confess too, for -8 > -20.
• If Mike choose to keep silent, Alex will confess anyways, for 0 > -1.
For both criminals, their dominant strategy* is the same:
They should confess, rather than risk that the other will confess if they
keep silent.
* The dominant strategy is the best strategy for a player to follow
regardless of the strategies chosen by the other players.
Group Exercise
Player 1
Cooperate
Defect
Cooperate
3/3
Rules:
1/4
Purpose: Win the
game by accumulating
the most points over 12
rounds
1/1
You may not speak to
your opponent to
conspire or reveal your
strategy.
Player 2
Defect
4/1
Questions
1. How does repeated play influence the outcome of prisoner’s dilemma?
2. What was your strategy? How did you determine it?
3. Did it work? Why or why not?