An ectotherm is an animal that relies mainly on heat from its surroundings to warm its body. Its body temperature varies with the environmental temperature. Reptiles, amphibians, fish and invertebrates such as insects are ectotherms.
Ectotherms produce some heat from respiration, but they have a low metabolic rate and little insulation, so this heat is quickly lost. Instead they gain heat mainly by absorbing radiation from the Sun and by conduction from warm surfaces such as rocks. Many control their temperature to some extent by behaviour, for example basking in the sun or moving into shade, and a few make simple physiological changes, such as some lizards darkening their skin to absorb more radiation.Advantages
• Very little energy from food is used to produce heat, so they need much less food than endotherms of the same mass.
• More of their energy intake can go into growth and reproduction.
• They can survive long periods without food.Disadvantages
• When it is cold, enzyme activity and metabolism are slow, so they are sluggish and less active, for example in the early morning, at night and in winter.
• Being slow when cold makes them more vulnerable to predators.
• They are less able to live in very cold habitats, and many become dormant in winter.For example, a lizard basks on a rock in the morning until its body has warmed up enough for it to hunt insects efficiently. On a cloudy, cold day it may stay hidden and not feed at all.
Ectotherms produce some heat from respiration, but they have a low metabolic rate and little insulation, so this heat is quickly lost. Instead they gain heat mainly by absorbing radiation from the Sun and by conduction from warm surfaces such as rocks. Many control their temperature to some extent by behaviour, for example basking in the sun or moving into shade, and a few make simple physiological changes, such as some lizards darkening their skin to absorb more radiation.Advantages• Very little energy from food is used to produce heat, so they need much less food than endotherms of the same mass.
• More of their energy intake can go into growth and reproduction.
• They can survive long periods without food.Disadvantages
• When it is cold, enzyme activity and metabolism are slow, so they are sluggish and less active, for example in the early morning, at night and in winter.
• Being slow when cold makes them more vulnerable to predators.
• They are less able to live in very cold habitats, and many become dormant in winter.For example, a lizard basks on a rock in the morning until its body has warmed up enough for it to hunt insects efficiently. On a cloudy, cold day it may stay hidden and not feed at all.