The ability of an organism to maintain its metabolic rate is affected by external abiotic factors.

Abiotic factors include temperature, salinity and pH.

Conformers’ internal environment is dependent upon external environment.

Conformers use behavioural responses to maintain optimum metabolic rate.

Behavioural responses by conformers allow them to tolerate variation in their external environment to maintain optimum metabolic rate.

e.g. sun basking to raise body temperature

Conformers have low metabolic costs.

Conformers have a narrow range of ecological niches.

Regulators maintain their internal environment regardless of external environment.

Regulators use metabolism to control their internal environment.

Regulators have an increased range of possible ecological niches compared to conformers, as they use metabolism to control their internal environment.

Regulators have increased metabolic costs as regulation requires energy to achieve homeostasis.

Regulation requires energy to achieve homeostasis, which is the maintenance of a constant internal environment .

Thermoregulation is achieved by negative feedback.

— The hypothalamus is the temperature monitoring centre — it plays a role in thermoregulation by monitoring the temperature.

— In thermoregulation, information from the hypothalamus is communicated by electrical impulses through nerves to the effectors.

— The effectors bring about corrective responses to return temperature to normal.

Regulating temperature (thermoregulation) is important for optimal enzyme activity and high diffusion rates to maintain metabolism.

The body has corrective responses to an increase in body temperature.

— sweating: body heat used to evaporate water in the sweat, cooling the skin.

— vasodilation: increased blood flow to the skin increases heat loss.

— decreased metabolic rate: less heat produced.

The body has corrective responses to a decrease in body temperature.

— shivering → muscle contraction generates heat.

— vasoconstriction: decreased blood flow to skin decreases heat loss.

— hair erector muscles contract: traps layer of insulating air.