Warm Blooded vs. Cold Blooded: How cold can you go?

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Difference between Warm Blooded and Cold Blooded

Warm blooded and cold blooded classifications are both biological terms that distinguish between animal species and how they regulate their body temperatures. The two terms are used to classify whether a species can maintain their heat and withstand cold temperatures and if they are able to regulate their bodies in such a way to withstand warm temperature climates.  Although this classification refers exclusively to temperature regulation and adaptability of the organism, it also has its deep roots in other classifications that define which animal species an organism belongs to. These classifications help to organize organisms according to their abilities to adapt to their environments as a whole.

Warm Blooded
Cold Blooded

Biological Terms 

A warm-blooded animal or its Latin derivative homeothermic animal species, is an organism that can maintain thermal homeostasis. Homeostasis describes the ability of the organism to regulate its own temperature to adapt to warm and cold weather at a consistent temperature level, regardless of the external temperature surrounding it. In order to be able to maintain a consistent internal temperature, the organism must be able to cool down to adapt in warm weather or to produce heat in a colder climate. They, in effect, can autonomically regulate the internal temperature of their bodies according the external influences placed upon them. Cold-blooded is a classification of organism who has the inability to adapt to the acclimate demands placed upon it. They are also referred to as ectothermic organisms or disambiguation.  Unlike warm-blooded organisms, cold-blooded organisms are unable to regulate their body temperatures to protect the organism from the extremes that it incurs around it naturally. 

Staying Cool and Keeping Warm

Warm-blooded animals are able to control their body temperatures by regulating their metabolic rates. They are able to increase their metabolic rate when confronted with a cold climate, increasing their internal temperature. In turn, they are able to decrease their metabolic rate when confronted with a warmer climate and need to cool down their internal temperature. As with most scientific classifications, however, as our understanding and instruments of measurements continue to increase our understanding of these classifications have grayed the areas between the two classifications and have made them less standard and less reliable. Cold-blooded animals do not have the ability to autonomously regulate their internal temperature and are therefore, limited in their adaptability to different climates. Cold-blooded animals are usually classified as those contrary to mammals or birds, which consists mostly of reptiles.

Science Progresses

Although being primarily layman’s terms throughout the scientific community, up until the last couple decades these terms were thought to be good classification tools for species.  Over the past 30 years, scientists have begun to see that the line that defines warm-blooded versus cold-blooded animals is not as clear as once thought. With the findings of animal species that fit into neither category completely, there arises the argument whether the classifications themselves really have any relation to defining the organisms.  In the past three decades thermophysiologists (scientists who specialize in temperature classifications), have added additional classifications such as poikilothermic and bradymetabolic, and found that some organisms are capable of wavering between the three classifications at any given point.


  • Warm-blooded organisms can regulate their own temperature
  • Cold-blooded organisms are not capable of regulating their own temperature
  • Although once thought to be a good classification, innovative scientific discoveries have lessened the divide between the ability of the two organisms in relation to temperature regulation.

Which one fares better during global warming?
  • Warm Blooded
  • Cold Blooded

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