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William Holder

Communication & Homeostasis
a) Outline the need for communication systems within multicellular organisms, with reference
to the
need to respond to changes in the internal and external environment and to coordinate the
activities of different organs
Organisms need to respond to external stimuli e.g. Temperature, Oxygen conc. &…

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temperature.
Physiological: The horned lizard expands its ribcage & frilled lizard expands its frills to absorb
more heat due to a larger surface area exposed to the sun.
Behavioural: Snakes expose their body to the sun, so more heat is absorbed. Locusts
orientate their body in the direction of the…

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William Holder
Physiological:
· Sweat glands in skin. If body temperature is high, the sweat glands secrete sweat which
evaporates, cooling the body. If it is too cold, less sweat is secreted so less evaporated,
therefore less heat loss.
· There are hairs on the skin, if it is too…

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William Holder

Nerves
a) Outline the roles of sensory receptors in mammals in converting different forms of energy
into nerve
impulses.
Sensory receptors are specialised cells that can detect changes in our surroundings. They are
energy transducers ­ they convert energy from one form to another. Each transducer is
adapted…

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