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• Inheritance• Variability• Limited resources• Selection

Evolution

Evolution is not random!

Evolution has no goal or pre-determined direction

Note:

Lines of Evidence

• 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 DiversityAnimals: estimated 3-30 million species||--Invertebrates: 97% of all known species| `--+--Sponges: 10,000 species| |--Cnidarians: 8,000-9,000 species| |--Molluscs: 100,000 species| |--Platyhelminths: 13,000 species| |--Nematodes: 20,000+ species| |--Annelida: 12,000 species| `--Arthropods| `--+--Crustaceans: 40,000 species| |--Insects: 1-30 million+ species| `--Arachnids: 75,500 species|`--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

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.

Introduction to Game Theory

*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

Stay Silent Confess

Stay Silent -1\-1 -20 \ 0

Confess 0 \ -20 -8\-8

Payoff Matrix

Alex’s Decision

Mike’sDecision

• 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

Player 2

Cooperate

Cooperate

Defect

Defect

3/3 1/4

1/14/1

Purpose: Win the game by accumulating the most points over 12 rounds

You may not speak to your opponent to conspire or reveal your strategy.

Rules:

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?