Page 344 - Biology_F5

Regulation (Homeostasis)

body requires increased food consumption; common way, as many ectotherms use
that is why animals feed on large amount the sun’s rays to warm up their bodies.
of food in cold climates. Reptiles and some amphibians bask in the
sun with their bodies spread out to increase
Temperature regulation by ectotherms the surface area for heat absorption. When
Ectotherms regulate their body temperature it is too hot, they hide in the shade or near
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mainly by behavioural means, depending on water bodies; allowing their bodies to
external heat sources; since these organisms cool.
do not have temperature control centre like (d) Clustering
endotherms. The exchange is controlled by Some animals exhibit group behavioural
three factors, namely radiation, conduction mechanisms to regulate their body
and flow. Their body temperature rises temperatures. A good example is how honey
and falls along with the temperature of the bees cuddle together in large groups to retain
surrounding environment. Although they and generate heat. A similar example is how
generate metabolic heat like endotherms, they some gregarious caterpillars bask in the sun
cannot increase heat production to maintain in large groups to gather heat.
an internal body temperature. Most of the
adjustment mechanisms are by behavioural (e) Burrowing
means such as: huddling, hibernation, Some ectotherms burrow themselves and
burrowing, aestivation, clustering, migration, hide deep into the ground. This helps them
and exposing themselves to the sun in hot to survive in cold environments.
environment.
(f) Aestivation
(a) Huddling Some ectothermic animals like earthworms,
In cold regions, animals are usually active snails, frogs, crocodiles, lizards, and tortoise
during the day. Huddling of individuals maintain their body temperature by
is also another common way of reducing reducing body metabolic activities and
heat loss. Some animals are able to crowd protecting themselves from very high
together in a tightly packed group to keep temperature. During summer time, some
them warm and reduce much heat loss animals usually tend to rest in shady or
when an individual animal is exposed cool places. Normally, they take a sleep
to cold open air. Therefore, this is also a during hot hours of daytime as a means of
means of conserving heat. avoiding environmental stress.

(b) Hibernation
Some animals in cold climates undergo Some ectotherms have developed some
a period of long sleep. During this time, chemical processes to survive the cold.
the metabolic rate is reduced 20-100 These animals, such as chorus frogs,
times below normal which consequently and gray tree frogs endure the cold by
reduces food and oxygen utilisation. undergoing chemical changes to prevent
their tissues from freezing. Other animals

(c) Sun basking such as wood frog can tolerate and regulate
Ectothermic animals may use radiant heat a frozen state by changing the chemical
provided by the environment to warm composition of their blood to a sugary state
their bodies. Solar radiation is the most that helps them avoid freezing.

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