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Lungs?; What else might work?
Topic Started: Feb 13 2010, 01:20 PM (760 Views)
sam999
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Is there any other way for getting oxagen into a body that works as well as lungs and could be used by a larrge creature?

EDIT. Must be for use on land.
Edited by sam999, Feb 14 2010, 12:44 PM.
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Holben
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Zorku
Mar 21 2010, 11:18 AM
We don't chew things in our nose but the nose joins up at the back of our throat where we need to switch the larynx's role to mostly one purpose of the other. Because we only swallow occasionally we can handle giving up most of the air flow for a few seconds at a time. Imagining your own bowel movements interrupting your breath is unrealistic because a small animal just evolving gas exchange wouldn't store up nearly as much waste or need to go to much effort to expel it. After the alternative lungs were in place evolutionary constraints would limit bowel movements to only the types still possible with breathing of concern.
The nasal passages allow air to come through when the mouth is shut, and food doesn't exactly fill your mouth unless you are one greedy pig. A lot of air is ingested along with the food we eat, hence its loss quickly afterwards.

A small animal can breathe dermally, so why?

Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea.

"It is the old wound my king. It has never healed."
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Zorku
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You seem to not understand that I'm talking about swallowing. You know, when the food goes down your throat? When that spot where the airway and the foodway use the same section of tubing? Food in your mouth is not a problem, it's when it's in your throat that matters.

Likewise the only time fecal matter would be an issue would be while it was moving through a particular stretch of the pipe works.
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The same reason we developed lungs that came through our mouth.

But take a quick gander at fish and notice how they have no nose. If airflow was around the back you might very well place chemoreceptors in a secondary cavity around the back. This would ultimately mean trouble for any animal trying to specialize in directional smell, as walking in a direction your eyes can't see tends to be less than effective. Growing eyes on the back and losing the ones on the front makes for a silly image of an animal that eats with it's butt but a twisted body plan like that of a snail would be a near infinitely more likely route for evolution to take at that point. This would be somewhat at odds with the spacing of paired appendages in fish but those would probably be more malleable before becoming load bearing structures.
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colddigger
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fish have nostrils.

i'm pretty sure they connect to the mouth since fish take water in through the mouth and pump it through their gills. that action is probably the only reason we can breath through our mouths, since our ancestors already took oxygen in through that opening anyway...
Oh Fine.

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Zorku
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Nope. The fish "nose" isn't connected to to the mouth at all. Hence I didn't consider it much of a nose.

Upon light google research I've found that the "out" pair of nostrils on fish migrated into the mouth in tetrapods giving us that second path for air that we prefer to breath through.
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colddigger
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oh snaggle!
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Holben
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Zorku
Mar 21 2010, 12:52 PM
You seem to not understand that I'm talking about swallowing. You know, when the food goes down your throat? When that spot where the airway and the foodway use the same section of tubing? Food in your mouth is not a problem, it's when it's in your throat that matters.

Likewise the only time fecal matter would be an issue would be while it was moving through a particular stretch of the pipe works.
-

The same reason we developed lungs that came through our mouth.

But take a quick gander at fish and notice how they have no nose. If airflow was around the back you might very well place chemoreceptors in a secondary cavity around the back.

Ignoring the contentious tone, i'd like to point out that swallowing uses air. Wow. Swallow now, feel the oesophagus begin to expand then contract. Food is pushed down by these contractions, and spends about 9 seconds before going through a sphincter into the stomach. Along with this food, already mashed up and full of air which can reach the lungs, a lot of air is drawn down by the changes which is partially sucked into the lungs through the back of the epiglottis.

I dunno about you, but our fecal matter remains in our rectum for a while before passing out. It fills up the rectum brfore the significantly long and vlnerable process of defecation, which causes more air to escape than exchange.

Fish allow oxygen to diffuse through the gills straight into the blood, impractical on land.
Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea.

"It is the old wound my king. It has never healed."
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Zorku
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As I was saying the way we poop would be very bad for breathing. Filling up the space directly behind the opening oft times with liquid would be a surefire way to suffocate but with a quick glance at our reproductive systems you can see that our bodies are more than capable of designs where waste material only occupies a bit of tubing very temporarily.

Furthermore there would be a nice window for adaptation during the intermediate phase of switching to gas exchange. Because the rectum empties periodically and moving about outside of the water would be a temporary effort at first the creature would need only empty its bowels before trudging about on land. With such a behavior in place the rectum could easily migrate back into the body leaving behind a chamber that would eventually expand for specialization in gas exchange. Defecation need only interrupt the process infrequently and perhaps even incompletely like swallowing does.
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