Evolutionary Fitness Calculator
Calculate relative fitness of genotypes from reproductive output. Fitness W = reproductive output / maximum output. Selection coefficient s = 1 - W. Understand how fitness differences drive allele frequency change.
🧬 Evolution📐 W = offspring / max offspring🧬 Biology
Offspring count for genotype AA
Offspring count for genotype Aa
Offspring count for genotype aa
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Evolutionary Fitness Calculator | — | W = offspring / max offspring | relative fitness |
Step-by-Step Examples
Example 1
Sickle Cell
AA=10, Aa=11, aa=6 (in malaria region).
- Max=11 (Aa), W(AA)=0.909, W(Aa)=1.0, W(aa)=0.545
- Aa has highest fitness (heterozygote advantage)
- h<0: overdominance maintains both alleles
- Explains balanced polymorphism for HbS
✓ Heterozygote advantage — balanced polymorphism
Example 2
Dominant Beneficial Allele
AA=10, Aa=10, aa=6.
- W(AA)=W(Aa)=1.0, W(aa)=0.6
- h=0 (A fully dominant)
- aa individuals have selection against them
- s(aa)=0.4
✓ h=0, A dominant beneficial allele
Example 3
Additive Fitness
AA=10, Aa=8, aa=6.
- W: 1.0, 0.8, 0.6
- h=(1-0.8)/(1-0.6)=0.5: additive
- Each A allele contributes equally to fitness
- s per allele = 0.2
✓ Additive fitness, h=0.5
Real-World Applications
Population Genetics
Fitness values drive allele frequency change in quantitative models.
Conservation
Fitness of hybrid genotypes determines viability of translocated individuals.
Plant Breeding
Fitness components (germination, growth, seed set) measured across genotypes.
Experimental Evolution
Track fitness changes in evolving laboratory populations.
Common Mistakes to Avoid
⚠️
Confusing absolute and relative fitness
Relative fitness W is always 1.0 for the most fit genotype. Absolute fitness (actual offspring number) varies with conditions.
⚠️
Ignoring environmental variation
Fitness is environment-specific. A fit genotype in one environment may be unfit in another.
⚠️
Single trait not total fitness
Total Darwinian fitness includes all components: survival, mating success, fecundity, offspring quality.
Frequently Asked Questions
What is fitness in evolution? ▾
The reproductive success of a genotype relative to others in a population. W=1.0 for most fit; W<1.0 for less fit. Difference drives allele frequency change.
What is selection coefficient s? ▾
s = 1 - W. s=0: neutral. s=0.1: 10% fitness reduction. s=1: lethal. Determines speed of selection.
What is dominance coefficient h? ▾
h measures how much the heterozygote resembles the less fit homozygote. h=0: A dominant. h=0.5: additive. h=1: a dominant. h<0: overdominance.
What is mean population fitness? ▾
Mean fitness W_bar = sum over genotypes of (frequency x fitness). Natural selection maximizes W_bar (Fisher's Fundamental Theorem).
What causes balancing selection? ▾
Heterozygote advantage (overdominance), frequency-dependent selection, or spatially varying selection. Maintains both alleles at intermediate frequencies.