Key Concepts of Evolutionary Fitness Measures to Know for Evolutionary Biology

Understanding evolutionary fitness measures is key to grasping how species adapt and survive. These concepts, like absolute and relative fitness, reveal how individuals contribute to their populations and the gene pool, shaping the course of evolution.

1. Absolute fitness

   • Measures the total number of offspring an individual produces over its lifetime.
   • Indicates the overall contribution of an individual to the gene pool of the next generation.
   • Can be influenced by environmental factors and individual traits.

2. Relative fitness

   • Compares the absolute fitness of an individual to that of others in the same population.
   • Expressed as a proportion, often relative to the most fit individual (set to 1).
   • Helps to understand how natural selection favors certain traits over others.

3. Inclusive fitness

   • Considers an individual's genetic success through both direct reproduction and the reproduction of relatives.
   • Highlights the importance of altruistic behaviors that benefit kin.
   • Expands the concept of fitness beyond individual survival and reproduction.

4. Darwinian fitness

   • Synonymous with reproductive success, emphasizing the survival and reproduction of individuals.
   • Reflects the ability to pass on genes to the next generation.
   • Central to the theory of natural selection, where advantageous traits increase fitness.

5. Reproductive success

   • Refers to the number of offspring an individual produces that survive to reproductive age.
   • A key measure of fitness in evolutionary biology.
   • Influenced by factors such as mate choice, parental care, and environmental conditions.

6. Survival rate

   • The proportion of individuals in a population that survive to a specific age or stage.
   • Affects overall fitness by determining how many individuals can reproduce.
   • Can be influenced by predation, disease, and resource availability.

7. Fecundity

   • The potential reproductive capacity of an individual, often measured by the number of eggs or seeds produced.
   • High fecundity can lead to greater reproductive success if offspring survive.
   • Influences population dynamics and evolutionary strategies.

8. Viability

   • Refers to the likelihood of an individual surviving to reproductive age.
   • Affected by genetic health, environmental conditions, and competition.
   • Important for understanding population stability and evolutionary pressures.

9. Selection coefficient

   • A measure of the relative fitness of a phenotype compared to others in the population.
   • Indicates the strength of natural selection acting on a trait.
   • Values range from 0 (no selection) to 1 (complete selection against a trait).

10. Adaptive landscape

    • A conceptual model representing the fitness of different genotypes in a population.
    • Visualizes how populations can evolve over time through peaks (high fitness) and valleys (low fitness).
    • Helps to understand the dynamics of evolution and the impact of environmental changes on fitness.