Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: John Harrison on 26/06/2009 16:30:02
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John Harrison asked the Naked Scientists:
Cold Bloodedness: We all know that reptiles must sun themselves in order to build the energy / ability to sustain activity. This attribute is generally attributed to the fact that they are cold blooded.
How then is it possible for other cold-blooded species (fish, invertebrates such as octopus, squid, etc.) to sustain high levels of activity in near freezing water?
What do you think?
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For an important chemical reaction, poikilotherms [cold-blooded animals] may have four to ten enzyme systems that operate at different temperatures. As a result, poikilotherms often have larger, more complex genomes than homeotherms [warm-blooded animals] in the same ecological niche. Frogs are a notable example of this effect.
Because their metabolism is so variable, poikilothermic animals do not easily support complex, high-energy organ systems such as brains or wings.[citation needed] Poikilothermic animals do not use their metabolisms to heat or cool themselves. For the same body weight, poikilotherms need half to 1/10 of the energy of homeotherms, and thus eat half to 1/10 of the biomass.
source: http://en.wikipedia.org/wiki/Poikilotherm (http://en.wikipedia.org/wiki/Poikilotherm)
So to answer your question: They have specialized enzymatic systems.
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Listen to the answer to this question on our podcast. (http://www.thenakedscientists.com/HTML/podcasts/show/2009.10.11/)
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Can cold blooded animals live in warm water?????
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cold blooded animals have that skin that protect them
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cold blooded animals have that skin that protect them
Skin alone is insufficient for temperature regulation in a cold climate.
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On the "cold-blooded" point, this brings up something I've wondered about. Dolphins.
These originated, according to conventional evolutionary theory, from ancestors that lived in the sea. Where they were, presumably, cold-blooded.
Then these ancestors came out of the sea and evolved to live on land. Where they became warm-blooded mammals.
Then these land-living mammals, for not very clear reasons, took a kind of retrogressive step, by going back into the sea again.
And this brings up the thing that puzzles me. When they went back into the sea - why didn't they go back to being cold-blooded again?
Why did they stay warm-blooded? I mean if they were going to retrogress by going back into the sea, shouldn't they have gone the whole hog, so to speak. And lost not just their land-based legs, which degenerated into fins and flippers, but their entire warm-body metabolism.
And so turned into versions of comparably-sized cold-blooded fish such as sharks.
Sharks seem to do very well by being cold-blooded. So why are dolphins still warm-blooded?
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Some sharks are warm-blooded.
There are advantages to being warm-blooded over cold-blooded, such as the ability to retain high energy levels despite cold conditions. That would give them an edge when hunting cold-blooded prey or escaping cold-blooded predators.
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Sharks seem to do very well by being cold-blooded. So why are dolphins still warm-blooded?
One reason is that it takes a lot of oxygen to maintain an active lifestyle and a large brain.
- This is an ecological niche which was not filled by fish
- It easier to get this oxygen from the air than it is to extract it from sea water.
Well-oxygenated surface water may only contain around 8 mg O2/l, while the air contains 210 mg O2/l.
See: https://rwu.pressbooks.pub/webboceanography/chapter/5-4-dissolved-gases-oxygen/