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Negative feedback Positive
Reversal of a change in
the internal
environment to return to
feedback
Increases the original
chance detected by
a steady state
receptors.
Optim
um STIMULU
conditi S­
on change
away from
optimum
EFFECT
OR ­
reverse RECEPT
the OR
change COMMUNICATI
ON SYSTEM -
nervous system
or hormonal
(endocrine)…read more

Slide 4

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ECTOTHER ENDOTHERMS
MSresources to help
Rely on external Independent of external temperature; use
maintain their body temperature. internal sources of heat to help maintain
their body temperature.
Advantage: Advantages:
More energy from food is used for growth Activity in cooler temperatures
Survive longer periods without eating Inhabit cooler parts of earth
Use less of their food in respiration. Whatever the external temperature they keep
a constant internal temperature
Disadvantages:
Less active in cooler temperatures Disadvantage:
No activity during winter More energy is used to maintain body
temperature in the cold
Less energy from food is used for growth
Examples:
Expose body to sun ­ snakes e.g. basking use
Example (if temperatures are too high):
frill to absorb the heat ­ lizards
Sweat glands in skin secrete more sweat -
Orientate body to the sun ­ locusts
more water evaporates = more loss of latent
Hide in burrow - lizards
heat.
Hairs on skin lie flat - less insulation = more
heat loss.
Vasodilatation ­ more blood in capillaries
close to the surface of the skin = more heat
radiated
Liver cells ­ metabolism reduced = less heat
generated.
Endotherms monitor the temperatures of
their blood in the hypothalamus. If core
temp drops the thermoregulatory centre in…read more

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NERVOUS SYSTEM
- Relay
neurons
Located within CNS
- Motor
neurons Conducts
impulses away
from CNS
- Sensory
neurons
Conducts impulses from
sensory receptors to CNS…read more

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