Ectotherm - Advantages and Disadvantages

Advantages and Disadvantages

Ectotherms will increase their body temperature mostly through external heat sources such as sunlight energy, therefore they depend on the occurring environmental conditions to reach operational body temperatures. Endothermic animals mostly use internal heat production through metabolic active organs (liver, kidney, heart, brain, muscle) or specialized heat producing organs like brown adipose tissue (BAT). In general, ectotherms therefore have lower metabolic rates than endotherms at a given body mass. As a consequence they would also need higher food intake rates, which may limit abundance of endotherms more than ectotherms.

Because ectotherms depend on environmental conditions for body temperature regulation, they typically are more sluggish at night and in the morning when they emerge from their shelters to heat up in the first sunlight. Foraging activity is therefore restricted to the day time (diurnal activity patterns) in most vertebrate ectotherms. In lizards, for instance, only a few species are known to be nocturnal (e.g. geckos) and they mostly use a 'sit and wait' foraging strategy which may require less high body temperatures than active foraging. Endothermic vertebrate species are therefore less dependent on the environmental conditions and have developed a high variability (both, within and between species) in their activity patterns across the day .

It is thought that the evolution of endothermia was crucial in the development of mammalian species diversity in the Mesozoic period. Their endothermic capabilities provided them with a benefit over the mostly ectothermic dinosaurs that dominated the Mesozoic era. Endothermia gave the early mammals the capacity to be active during night time and avoid higher predation risk during the day. Endothermia therefore may have contributed to the fact that most mammalian taxa were already present at the end of the Mesozoic (65 million years ago) and that most extent mammalian taxa thus went through an evolutionary bottle neck (the nocturnal bottleneck hypothesis).