Endotherm and ectotherm graph interpretation

How do you recognize BMR on an endotherm metabolic-rate graph?

It is the lowest flat region of the curve inside the thermoneutral zone.

How do you identify the lower critical temperature (LCT) on an endotherm graph?

It is the ambient temperature where metabolic rate first starts rising as temperature falls.

How do you identify the upper critical temperature (UCT) on an endotherm graph?

It is the ambient temperature where metabolic rate first starts rising as temperature increases above the TNZ.

If metabolic rate is still decreasing as ambient temperature rises, is the animal below or above the TNZ?

Below the TNZ.

If the line of an endotherm graph no longer fits the data at warm temperatures, what does that suggest?

The animal may have reached the upper part of the TNZ or gone above the UCT, so the simple cold-side linear trend no longer applies.

If a duck’s metabolic rate at 0°C is much higher than the minimum on the graph, is 0°C equal to BMR?

No.

If an endotherm’s graph shows no flat minimum between -20°C and 20°C, can you assume the LCT is below 20°C?

No. The LCT may be above or below that range depending on the graph; you need the flat minimum region to identify it.

What graph change would you expect if insulation increases in an endotherm?

The LCT shifts lower and the TNZ broadens.

What graph change would you expect if insulation decreases in an endotherm?

The LCT shifts higher and the TNZ narrows.

How do you estimate oxygen unloading from an oxyhemoglobin curve?

Subtract tissue saturation from arterial saturation, then multiply by carrying capacity if oxygen content is needed.

If Hb saturation is 95% in arterial blood and 40% in tissue-side blood, what percent of Hb-bound oxygen was unloaded?

About 55% of carrying capacity.

If oxygen carrying capacity is 20 mL O2 per 100 mL blood and Hb saturation is 40%, how much O2 is bound to Hb?

About 8 mL O2 per 100 mL blood.

At PO2 ≈ 25 mmHg on a standard human Hb curve, what is Hb saturation?

About 40%.

At PO2 ≈ 40 mmHg on a standard human Hb curve, what is Hb saturation?

About 70%.

At PO2 ≈ 85–100 mmHg on a standard human Hb curve, what is Hb saturation?

About 95–99%.

What does a left-shifted oxyhemoglobin curve mean at the same PO2?

Higher Hb saturation and higher oxygen affinity.

What does a right-shifted oxyhemoglobin curve mean at the same PO2?

Lower Hb saturation and lower oxygen affinity, which helps unloading.

What does a lower P50 mean?

Higher oxygen affinity.

What does a higher P50 mean?

Lower oxygen affinity.

If one species’ Hb curve is left-shifted relative to another’s, which species has the higher oxygen affinity?

The left-shifted species.

At the same PO2, which species is carrying more oxygen on hemoglobin: the one with higher saturation or lower saturation?

The one with higher saturation.