Temperature Regulation (Leaving Cert Biology): Revision Notes
📚 Revision Notes
Temperature Regulation
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Homeostasis: the maintenance of a constant internal environment.
- Plants: Plants can survive in a wide range of temperatures. Transpiration cool plants down.
- Animals: Some regulate temperature more easily than others. Humans maintain a constant temperature of 37°C.
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Transpiration is the loss of water vapour from the aerial parts of a plant.
Ectotherms
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Ectotherms are animals that cannot maintain a constant internal environment (e.g., reptiles, insects).
- Environmental temperature changes will cause a change in their internal temperature.
- Example: reptiles, insects.
Endotherms
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Endotherms are animals that can maintain a constant internal body temperature, despite changes in external temperature (e.g., mammals, birds).
- Endotherms' main source of heat is from metabolic reactions, which are controlled by thyroxine (a hormone produced by the thyroid gland).
To stay cool, endotherms:
- Sweat: Heat is lost as water evaporates from the skin.
- Vasodilate: Blood vessels widen to increase heat loss.
- Breathe rapidly: Heat is expelled through faster respiration.
To warm up, endotherms:
- Shiver: Skeletal muscles contract and relax, producing heat.
- Goosebumps: Hair stands up, trapping a layer of warm air close to the skin.
- Vasoconstrict: Blood vessels narrow, reducing blood flow to the skin and minimising heat loss, keeping vital organs (e.g. heart) warm while extremities get colder.
- Secrete thyroxine: Increases metabolic activity in body cells, generating heat.
Energy Demands:
- Endotherms eat more frequently than ectotherms due to high energy demands.
- Endotherms need a lot of energy to regulate their temperature, so they must eat large volumes of food at regular intervals.
- Ectotherms need less energy and can survive without food for long periods of time.