Building Evolutionary theory Flashcards
(14 cards)
Describe development of theory
Theoretical biology begins with the natural world.
By thinking about observations of the world, we conceive an idea about how it works - theory
Theory can be formalised using mathematical models that describe appropriate variables and processes
Describe the theory of evolution by natural selection
Darwin collected enormous amounts of information on artificial selection to make inference about natural selection
Describe the theory of competitive exclusion
Gause
A simple unstructred environment containing only a single resource can support only one competitor (Aurelia and Caudatum)
Describe kin selection theory
A behaviour is favoured when it leads to a net increase in the inclusive fitness of the actor
Describe mathematical models
Mathematical models are by definition abstractions of reality. We need to decide which assumptions to include (must be routed in biology)
Describe the process of building models
Dynamic.
Assumptions: choose key compoents, processes, variables
Model development: mathematical analysis, computer simulations
Model validation: experiments, observations.
Repeat
Describe generating hypotheses
Need to be testable
Difficult to verify a hypothesis through empirical confirmation
Therefore, hypothesis can only be falsified. They have to be falsifiable i.e. it should be possible to conceive of an experimental observation that disproves the idea in question
State what makes a theory scientific
Theories that are not falsifiable by any conceivable event are not scientific
Describe quantitative vs qualitative predictions
Both quantitative and qualitative predictions are important, but quantitative predictions allow easier falsification
e.g. kin selection theory makes qualitative predictions
Kimura’s neutral theory makes quantitative
Describe the predictions of kin selection theory
An altruistic (cooperative) act is able to spread through the population if
benefit to recipient x relatedness between altruist and those gaining benefit > cost to altruist
Captures potential general trends of when cooperation might or might not be favoured.
Not suited for quantittive predictions
To test kin selection theory, we need to calculate the core parameters, which is a non-trivial tast
Describe Kimura’s neutral theory
Quantitative predictions
Natural theory of molecular evolution combines population genetics theory and molecular evolution data
The hypothesis:
most molecular polymorphisms and substitutions are due to neutral mutations and genetic drift.
Describe predictions of neutral theory
- The ratio of the variance to the mean number of substittions on a lineageis R=1
- The expected heterozygosity under the equilibrium between mutations and random drift is (slide) where u is the mutation rate and N is population size
Give an example of testing kin selection theory
Invertase production in S. cerevisiae
Relatedness can be manipulated through spatial structure.
Structured: cooperators and cheats separate (high relatedness).
Unstructured: mixed, low relatedness
Both environments equally promoted cooperation. Have we falsified the theory? No, spatial structure hasn’t manipulated the relatedness, and sugars diffuse
Describe testing neutral theory
Computational tests show that heterozygosity does not increase as much as expected in large populations. Imprtantly, the qualitative trend is consistent.
The ratio of the variance to the mean number of substitutions on a lineage is R=1. Combining DNA sequence data and computer simulations, it was shown that R>1.
