Quantifying Biological Fitness: Selection, Inclusive Fitness, and Genetic Load

All flashcards

Biological fitness

The expected contribution of a genotype or phenotype to future generations in a specified environment.

Fitness as a propensity

An expected or average contribution across a class of individuals, not a guaranteed outcome for one individual.

Fitness and lifespan

Fitness concerns contribution to future generations; living longer does not necessarily mean leaving more descendants.

Environmental dependence of fitness

A trait’s effect on reproductive contribution depends on the selective environment.

Allele fitness in sexual populations

It can be estimated by averaging an allele’s effects across the genetic backgrounds where it occurs.

Quiz questions

1. Which measure describes a genotype’s proportional change in abundance over one generation due to selection?Answer: Absolute fitness
2. In a population subject to selection, what tends to happen to a genotype whose relative fitness is above the population mean?Answer: Its frequency tends to increase.
3. What does inclusive fitness account for?Answer: Effects on the focal individual’s reproduction and on other individuals sharing the allele, without double counting.
4. Why can the same phenotype have different fitness in different environments?Answer: Its effect on reproductive contribution depends on the selective conditions.
5. Why can relative fitness values alone not show whether a whole population is growing or shrinking?Answer: They compare genotypes but do not convey overall population abundance.