Science Notes
Chapter 3: Coordination and response (Homeostasis)
Definition of homeostasis:
Homeostasis refers to the maintenance of the internal environment in the body of an organism.
Type of homeostasis in the human body:
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Regulation of water content
Regulation of body temperature
Control centre
Increase
Corrective
mechanism
Decrease
Normal
temperature
Normal
temperature
Decrease
Control centre
Increase
Corrective
mechanism
Regulation of water content
Regulation of body temperature
High surrounding temperature (Hot)
- Sweat glands produce more sweat to cool the skin when
sweat is evaporated.
- Hairs lie flat to reduce air trapped on the skin so that heat
can be released easily.
- Blood vessels dilate to let more blood flow to close to the
skin increase heat loss
Lower surrounding temperature (Cold)
- Erect hairs trap a layer of air that acts as a heat insulator.
- Blood vessels constrict to let more blood flow away from the
skin to reduce heat loss.
Homeostasis in Animals
Examples of
animals
Cat
Dog
Lizard
Snail
Bee
Ways of homeostasis
Lick fur to reduce body temperature
Hang the tongue to reduce body temperature
Cold surrounding
• Body activities become slower
• Muscles function more slowly
• Movements become slower
• Metabolism rate decreases
• Body temperature decreases
Hot surrounding
• The heart beats faster
• Movements become faster
• Metabolism rate increases
• Body temperature increases
Produces fluid and looks for humid places to reduce water loss
Closes spiracles between two breathing movements to reduce water loss.
Homeostasis in Plant
Definition:
Transpiration is the evaporation of water from leaves in the form of water vapour to the surrounding through stoma.
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Transpiration helps plants to absorb and carry water and minerals from the soil to all parts of the plant.
Evaporation of water from the leaves cools the plant during the days.
Stomata
The small openings on
the underside of leaves
are called stomata
During the day: Stoma opens to enable more water to be evaporated from the leaves through transpiration.
During high temperature: Stoma closes to reduce water evaporated from the leaves through transpiration.
The importance of homeostasis to humans and living things:
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Provide the optimum conditions in the body.
The internal environment in the body is regulated and maintained in a balanced and stable condition.