Temperature-size rule

[9] His rule postulated that selection favored within species individuals with larger body sizes in cooler temperatures because the total heat loss would be diminished through lower surface area to volume ratios.

This creates an inaccurate description of observed body size variation in ectotherms since they routinely allow evaporative heat loss and do not maintain constant internal temperatures.

His study, which included 92 species of ectotherms ranging from animals and plants to protists and bacteria, concluded that a reduction in temperature resulted in an increase in organism size in 83.5% of cases.

[18][19][20] In doing so, these individuals sacrifice growth to larger adult body sizes to ensure reproductive success, even if the trade-off results in smaller offspring that have increased mortality rates.

[20] Ectotherms occupying colder environments, such as mountain ranges or other areas of higher elevation, have been observed to invest in reproduction at larger adult body sizes due to a prolonged growth period.