This document compares and contrasts ectotherms and endotherms. Ectotherms, such as reptiles and fish, rely on external heat sources to regulate their body temperature, which rises and falls with the environment. In contrast, endotherms like birds and mammals internally produce heat to maintain a stable core temperature independent of the environment. The document discusses advantages and disadvantages of each, such as ectotherms requiring less food but becoming sluggish in cold weather, while endotherms can be active regardless of temperature but need more food and risk overheating.

1. Ectotherms vs
Endotherms

2. Ectotherms
The name ectotherm comes from the Greek “ektos”
meaning outside and “therm” meaning heat.
These are organisms which control their body
temperature through external means
They depend on environmental heat sources
Their body temperature rises and falls with their
environment

3. Examples of ectotherms
Reptiles
Fish
Insects
Plants
Invertebrates

4. Regulation of Temperature
Ectotherms have limited ability to
control their body temperature,
so they regulate it by
BEHAVIOURAL adaptations
Seeking shade or sunshine
Huddling together (bees)
Movement of
wings to absorb
light and warmth

5. BenefitsEctotherms tend to have low
metabolic rates
Energy is not being burnt to create
heat
Therefore less food is needed to
survive
◦ Snakes can eat as rarely as every 1-2
weeks
◦ Increased rates of
survival regardless
of food supply
This snake has eaten a dog

6. Disadvantages
When it is very cold, ectotherms become sluggish.
◦ They may not be able to escape from predators as easily
When it is very warm, ectotherms require
more food as their metabolic rate
increases
◦ They may be able to mitigate this by finding a cool place to rest

7. Endotherms
The name endotherm also
comes from the Greek, “endo”
meaning inside
These are organisms which
produce heat through internal
means
The internal temperature
is independent of the
outside temperature

8. Examples of endotherms
Birds
Mammals
(humans)
Marsupials
Monotremes

9. Regulation of Temperature
Endotherms require about 5 times as much food as
ectotherms of the same size
They have a lot more mitochondria per cell – the organelles
which make energy
A high rate of metabolism of fats and sugars generates a lot
of heat

10. Advantages
Endotherms can behave normally regardless of the
temperature by using behavioural modifications
◦ However, in extremes of temperature they may struggle to
maintain correct temperature

11. Disadvantages
When it is very hot, endotherms
may overheat, called
hyperthermia
◦ Panting, sweating, vasodilation
(flushing and blushing) are used to
cool down

12. Disadvantages
When it is very cold, endotherms
lose too much body heat, they
get hypothermia
◦ Insulation is used to prevent this – fur, feathers, hair, fat
deposits
◦ Vasoconstriction (reduced blood flow to extremities –
blue lips) retains
heat in the body
◦ Hibernation – controlled
hypothermia to reduce
metabolic rate

13. Hibernation
Physiological conditions during hibernation:
◦ Metabolic rate decreases
◦ Heart beat slows down to as low as 3bpm
◦ Breathing rate drops
◦ Body temperature decreases to close to ambient
temperature
◦ Must always remain above 0°C – why?

14. Hibernation
Preparation required for
hibernation
◦ Fat reserves must be built up to
provide an energy supply
◦ A suitable place to hibernate
must be found
◦ Amphibians burrow
underground
◦ Other organisms sleep
in a sheltered place

15. Review
Why might endotherms migrate between different
areas in summer and winter?
Why might some endotherms display nocturnal
behaviour?

16. Review
Is hibernation used only by endotherms or by
ectotherms as well?
Why is it important to find a suitable place to
hibernate?