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  Topic: Official Uncommonly Dense Discussion Thread< Next Oldest | Next Newest >  
Patrick Caldon

Posts: 68
Joined: April 2006

(Permalink) Posted: July 23 2007,23:34


Trying to find a definition of fitness is like trying to grab hold of jello.

Actually, it's about as hard as shelling out a few dollars for a textbook on the subject and reading it:


The fitness of a genotype measures its relative ability to reproduce itself, compared to other genotypes.

Fitness shows to what extent a genotype is favored by natural selection. Fitness values are between 0 and 1. The fittest individual has a fitness of 1, and the fitness of the other members of the population can be expressed as 1 - s, where s is the selection coefficient.

The fitnesses of different genotypes are among the most important variables - perhaps the most important variables - in the theory of evolution. They determine, to a large extent, which genotypes we can expect to see in the world today.

There are three methods for measuring fitness:

Measure the relative survival of the genotypes within a generation. Kettlewell's mark-recapture experiment with the peppered moth is an example.

Measure changes in gene frequencies between generations. We then substitute the measurements into the formula that expresses fitness in terms of gene frequencies in successive generations.

Measure deviations from the Hardy- Weinberg ratios - this is used in estimating fitness in the case of sickle cell anemia.

A measure of mean fitness is commonly applied in population genetics.

The idea of a fitness landscape is particularly useful for thinking about complex genetic systems.

  29999 replies since Jan. 16 2006,11:43 < Next Oldest | Next Newest >  

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