Life is Hot and Cold (Part III)


What makes me warm-blooded and my pet reptile cold-blooded, yet we both thrive?

You, and your pet reptile, are made of matter that must live within the physical and chemical laws of nature.  This means that you both must deal with heat, the transfer of energy from one object to another, and (core) temperature, the amount of internal energy and random motion of the molecules that make up your cells.  The core temperature for both of you is controlled by the hypothalamus.  You, and other mammals and birds, are called warm-blooded because your core temperature is mostly dependent on the release of heat during cellular respiration and can be kept relatively constant, usually warmer than the temperature of your surroundings.  In contrast, your pet and other reptiles, amphibians, insects and fish are called cold-blooded because their core temperature is mostly dependent on the temperature of their surroundings, which is constantly changing and, in the same surroundings, is usually colder than it is for warm-blooded animals. 

Just as a machine can malfunction if it’s too hot or too cold, so too, the cells that make up the organs of yours, and your pet reptile’s body, can malfunction if the core temperature is too high or too low.   Most of the enzymes your body uses for its vital metabolic processes work best within an ideal temperature range of about 97o-99oF (36oC-37oC).  Any significant rise above, or drop below, this range makes your metabolism run too fast or too slow which can impair brain and other organ function and cause muscle weakness.  The same applies to your pet reptile, and other cold-blooded animals, which although they (e.g. frogs) often have other enzyme systems that can be used at different temperatures, when it gets too cold their systems slow down too much so that they can barely move which puts them at a disadvantage to warm-blooded animals.  Warm-blooded animals are therefore able to forage for food faster and defend themselves better within a wider temperature range and are able to support highly-complex energy-dependent organs like the mammalian brain.  After all, your pet reptile only has to learn how to feed and defend itself and reproduce whereas you must do that and also learn to read, calculate, communicate, think, analyze, imagine, create, and do all the things unique to being human (my apologies to your pet reptile as we really don’t know what it’s like to be one).

Your, and your pet reptile’s, core temperature is directly related to how much heat its cells release from its metabolism and how much heat it loses to, or gains from, its surroundings.  If you’re too hot you can voluntarily go out of the sun and into a breezy shade or jump into a cool lake, and if you’re too cold you can come out of the breezy shade into the sun or jump into a hot spring.  Your pet reptile can do the same things but that’s about all.  But, your body can also do a lot of involuntary things to keep its core temperature relatively constant and usually warmer than your surroundings so your brain, organs and muscles can work properly to keep you alive. 

Inside the mitochondria of your cells is where cellular respiration takes place but they are only able to harness about one-quarter of the energy from this process and release the rest as heat.  This “inefficient” use of energy from cellular respiration in warm-blooded animals seems to be the main way that they keep their core temperature above their surroundings and has recently been determined to be mainly due to the effects of thyroid hormone.  This is why when someone doesn’t have enough thyroid hormone in their blood they tend to feel cold and when they have too much they tend to feel hot.  The cells of your pet reptile, and other cold-blooded animals, have fewer mitochondria which also seem to lack this effect of thyroid hormone, so they don’t release as much heat.   Also, if you’re too cold your hypothalamus can tell your muscles to shiver and your body to burn up fat to release more heat and tell the muscles surrounding the blood vessels in your skin to contract to reduce blood flow and limit heat loss.  And if you’re too hot it can tell the muscles surrounding the blood vessels in your skin to relax to increase blood flow to the skin, and turn on your sweat glands, to promote heat loss.  But all of these actions require a lot of energy that has to come from somewhere.   

Being warm-blooded and able to maintain tight control of your core temperature so complex organs, like your brain, can work properly requires that you use up more energy from the food you bring into your body.  In fact, warm-blooded animals must eat much more food, usually five to ten times more, than cold-blooded ones of a similar size.  Warm-blooded animals are nature’s equivalent of the gas-guzzling and energy-inefficient car since they use up so much fuel just to maintain their core temperature to keep their organ systems running properly.  And cold-blooded animals are eco-friendly and energy efficient because they don’t need to use up as much fuel to keep their organ systems running properly.

Conventional scientific wisdom says that warm-blooded animals evolved from cold-blooded ones.  Little else is said about how this evolutionary development could have taken place while allowing for survival capacity each step along the way.  In looking at a cold-blooded animal and considering the innovations needed to make it capable of being warm-blooded, one can see that this would be like converting a Model-T Ford into a Lexus.  Instead of cranking the engine to start, sitting in a drafty vehicle and moving in a herky-jerky motion from shifting gears, the modern driver electronically starts the engine from a distance, sits comfortably in a climate-controlled air-tight vehicle and enjoys smooth acceleration from the automatic transmission. 

This is a good example of how the more you understand what it takes for life to survive within the physical and chemical laws of nature, the more you come to realize how inadequate, overly simplistic and implausible the theories of evolutionary biologists who claim that the design we see in life is only apparent and not real. 

Three Questions for Mr. Darwin

    1. If cold-blooded animals evolved into warm-blooded ones, where did the information come from to make the transitional and eventual warm-blooded ones (like me) have the right amount of thyroid hormone and mitochondria in their cells to release enough heat from their metabolism?

    2. Compared to warm-blooded animals of the same size, cold-blooded ones (e.g. frogs) seem to have more genes to produce different enzyme systems that work at different temperatures to survive, so where did the information come from to tell organisms that were transitioning from being cold-blooded to warm-blooded which genes and enzyme systems to get rid of each step along the way and how did they survive?

    3. For me to have a highly complex energy-dependent brain that, among other things, can maintain strict control of my core temperature so I can be warm-blooded, first required me to be warm-blooded, so where did all the new information come from to accomplish this core temperature control and which came first?   

 


Also see Dr. Glicksman's Series on

"Beyond Irreducible Complexity"

"Exercise Your Wonder"


Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.

Comments and questions are welcome.

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