How does three chambers of heart help the amphibians?

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Discussion Overview

The discussion centers on the structure and function of the three-chambered heart in amphibians, exploring its efficiency and adaptations in relation to their physiology and environment. The scope includes theoretical aspects of cardiac design, evolutionary biology, and physiological adaptations.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes that amphibians can prevent blood from going through the pulmonary circuit, seeking clarification on this mechanism.
  • Another participant explains that oxygenated and deoxygenated blood mix in the single ventricle, resulting in less oxygen saturation in the body compared to a four-chambered heart, but suggests this is adequate for amphibians.
  • A different participant introduces the idea that being cold-blooded allows amphibians to function with a less efficient heart, mentioning their ability to divert blood flow to the skin for respiration during diving.
  • One participant comments on the evolutionary perspective, suggesting that the heart's design reflects a thrifty approach by nature, providing only what is necessary for survival.

Areas of Agreement / Disagreement

Participants express varying views on the efficiency and adaptations of the three-chambered heart, with no consensus on the overall implications of these features for amphibians.

Contextual Notes

Some assumptions about the efficiency of the three-chambered heart and its evolutionary significance remain unresolved, and the discussion does not clarify the implications of blood mixing in the ventricle.

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it seems that these kinds of animals can prevent blood going through the lung (pulmonary vein,artey)Can anyone clarify it please?
 
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Oxygenated blood returning from the lungs (into the left atrium) and deoxygenated blood returning from the body (into the right atrium) get mixed in the single ventricle, the ventricle then pumps part of this blood to the lungs and part to the rest of the body. This has the effect that the body will not get blood satured with oxygen but it is good enough even if it is less efficient than a four-chambered heart.
 
The fact that these are cold-blooded animals and are not expending a lot of energy in heat production probably factors into this. Thus, reptiles* and amphibians can survive with a less efficient cardiac design. They are also able to shut off pulmonary artery flow to divert blood to the skin for cutaneous respiration during diving which may also compensate for a less efficient heart.

*The crocodilians are the exception to this design in the cold-blooded realm and have a four-chambered heart. However they are also capable of shunting pulmonary blood flow while diving. This anatomical setup is believed to be the http://jeb.biologists.org/cgi/content/abstract/186/1/269in any vertebrate.
 
I guess this just goes to show that evolution is very thirfty. You only get what you proved (to nature) to need and not anymore.
 

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