Ectotherm performance and classification

Does an ectotherm’s metabolic rate always increase as ambient temperature rises?

No. It usually rises up to an optimum, then declines as high temperatures become stressful or damaging.

What usually happens to ectotherm performance at temperatures above the pejus temperature (Tp)?

Performance begins to decline and the animal enters a stress region.

What does the pejus temperature mark on an ectotherm curve?

The point near maximum performance where further warming leads into declining performance or stress.

At the upper critical temperature (UCT) of an ectotherm, is normal function starting to fail?

Yes.

Is an ectotherm more likely to survive at its UCT or its ULT?

At its UCT. ULT is lethal.

In an ectotherm, is metabolic rate at UCT necessarily greater than at the pejus temperature?

No. By UCT, performance and metabolism may already be declining.

What is the difference between To and Tp on an ectotherm graph?

To is the thermal optimum or preferred temperature; Tp marks the start of the decline/stress region near peak performance.

Does shuttling usually help an ectotherm reach its maximum metabolic rate?

No. Shuttling usually helps it stay near preferred or optimal temperatures, not maximize metabolic rate at all costs.

What is optimal metabolic rate (OMR)?

The metabolic rate at the thermal optimum.

Is the optimal metabolic rate in an ectotherm always equal to the maximum metabolic rate?

No. They are not necessarily the same.

In this course’s simplified usage, are all thermoconformers ectotherms?

Yes.

Are all ectotherms thermoconformers?

No. Many ectotherms behaviorally regulate temperature.

Can a homeotherm be ectothermic?

Yes. If the environment is very stable, an ectotherm can maintain a fairly constant body temperature.

Can an endotherm be heterothermic?

Yes. Some endotherms use torpor or hibernation and do not maintain a constant body temperature all the time.

What is the key difference between endotherm/ectotherm and homeotherm/poikilotherm?

Endotherm vs ectotherm describes the source of heat; homeotherm vs poikilotherm describes stability of body temperature.

Compared with a eurytherm, what kind of thermal range does a stenotherm have?

A narrower environmental temperature range.

In test-style comparisons, what value may be greater in a stenotherm than in a eurytherm?

Q10, because performance may change more steeply with temperature.

During acclimatization in an ectotherm, does only To change?

No. The whole performance curve can shift.