Temperature Regulation

• 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.

Ectotherms

• Environmental temperature changes will cause a change in their internal temperature.
• Example: reptiles, insects.

Endotherms

• 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:

1. Sweat: Heat is lost as water evaporates from the skin.
2. Vasodilate: Blood vessels widen to increase heat loss.
3. Breathe rapidly: Heat is expelled through faster respiration.

To warm up, endotherms:

1. Shiver: Skeletal muscles contract and relax, producing heat.
2. Goosebumps: Hair stands up, trapping a layer of warm air close to the skin.
3. 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.
4. 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.