The graph below shows the results of a laboratory investigation which measured the body temperatures of a lizard and a bird under changing artificial conditions. Use it to answer the question.
Which of the statements below is valid?
The bird's blood was always warmer than that of the lizard
The body temperature of the bird varied less than that of the lizard during changes in environmental temperature
The body temperature of the bird remained constant despite changes in environmental temperature
The body temperature of the lizard was always close to that of the environmental temperature
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The correct option is B.
This question aims to test one's knowledge of homoithermic and poikiolothermic organsims. Poikilothermic organisms (e.g., lizards, toads, fish) have body temperature which fluctuates or varies with the external or environmental temperture over a wide range just as can be seen on the graph. On the other hand, homoithermic organisms (e.g., birds, man) can only tolerate a minimal/ narrow range of body temperature variation despite a widely changing environmental temperature.
As shown on the graph, the temperature variation in bird is from 94 -104 degrees Farenheit, while the temperature variation in lizard is from 62 -110 degrees farenheit. When compared, it is logical to conclude that the 94 -104 temperature variation is narrow while the 62 -110 is wide. Thus, bird is homoiothermic while lizard is poikilothermic.
It should be noted however, that the bird does not have a constant body temperature (I mean, it's obvious). The body temperature varied, but within a narrow limit. It will therefore be safe to say the bird has a fairly constant body temperature not a constant one. That is the basis of homeostasis; there is a little deviation which is always corrected in time before it gets too wide or beyond what the organism can tolerate.
You can also think about it this way; as humans, we are homoiotherms but none of us will have the same body temperature every single moment we measure it. Why? Because there is room for a little variation in the parameters we measure in our body.
In summary, the 94-104 degrees Farenheit temperature varaition seen in bird (on the graph) is a variation, not a constant value but it is a minimal variation. Also, the 62 - 110 degrees Farenheit temperature variation seen in lizard is also a variation ( a wide one at that).
