Enter your species' Reproductive Rate (r), Carrying Capacity (K), Initial Population, Offspring per Event, and Survival Rates into the r and K Selection Calculator to find your Selection Strategy Type, Final Population, Growth Rate, and Reproductive Value.
Selection Strategy Type
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Final Population Size
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Population Growth Rate
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Reproductive Effort Index
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K-Strategy Score
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r-Strategy Score
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r-selection favors high reproductive rates and rapid population growth in unstable environments, while K-selection favors competitive ability and stable populations near carrying capacity. r-strategists produce many offspring with low survival rates, while K-strategists produce fewer offspring with higher survival rates.
Higher r-strategy scores indicate organisms that reproduce quickly with many offspring, typical in unstable environments. Higher K-strategy scores suggest organisms with longer lifespans, fewer offspring, and greater parental investment, typical in stable, competitive environments.
r-selected species include bacteria, weeds like dandelions, insects, and small mammals like mice. K-selected species include elephants, primates, large trees, and humans - species with long lifespans and extensive parental care.
Carrying capacity (K) represents the maximum population size an environment can sustain. As populations approach K, growth rates slow due to increased competition for resources, following the logistic growth model.
Unstable, unpredictable environments with frequent disturbances favor r-selection, while stable, predictable environments with intense competition favor K-selection. Climate variability, resource availability, and predation pressure all influence these strategies.
Yes, most species fall somewhere on a continuum between pure r and K strategies. Many organisms can shift their reproductive strategies based on environmental conditions, displaying phenotypic plasticity in their life history traits.
r-selected species typically have short generation times, reaching reproductive maturity quickly. K-selected species have longer generation times, investing more time in growth and development before reproducing.
The reproductive effort index measures the proportion of an organism's resources allocated to reproduction versus survival and growth. Higher values indicate greater investment in reproduction (r-strategy), while lower values suggest more investment in survival (K-strategy).