Why do mamals, birdies, fishies and many other creatures have two nostrils? Do any have three? Does an elephant have one or two? Just wondering… :rolleyes:
Last time I saw the business end of an elephant’s trunk I saw two nostrils. I assume the elephant must have an 8-foot septum.
Nature seems to favor bilateral symmetry.
Wouldn’t you still have bilateral symmetry if you had only one nostril? If you cut a person in half and created a mirror image of one of the halves you would be left with a whole person, with one nostril.
Then why not two nostrils on each side? 
I think this might provide the answer.
It seems it may just be a hangover from the fish we evolved from, who needed to have two nostrils to allow water to flow through rather than causing drag.
Isn’t it odd though that we have two of many things we dont really need to live (arms, legs, eyes, ears, nostrils), yet we have only one heart.
I always found it odd that our ousides are so bilaterally symetrical, but our innards aren’t. (Except for the bones and the kidneys.) Seems like the outards would be less important than the innards.
What’s “important” isn’t a determining factor here. It’s a combination of what works and what an organisms predecessors had.
The digestive innards and their related glands are variations on one long tube from mouth to exit.
Most of the other innards – reproductive gizzards, kidneys, lungs – are bilaterally symmetrical.
The heart, while it’s not part of a pair, and is not *exactly * symmetrical, is a variation on a bilateral form. It’s got a left and a right half, a top and a bottom half, but some parts have developed into larger structures is all.
Reproductive gizzards??
You do know what gizzards are used for don’t you?
Hint…they ain’t reproductive.
Also, note that the heart, while singular, begins as two endocardial tubes (click on the “formation of the heart tube” link from there), which later fuse as development progresses.
I was speaking metaphorically. Gizzards = innards.
If we were being technical, gizzards generally = poultry stomachs.
Very well explained, as usual. Thank you. Do you teach this stuff?
Close
The gizzard is the second part of the stomach. Most fowl will eat small stones that situate themselves in the gizzard to grind seed and other hard foods the bird eats.
Yep…I’m a country boy.
How can you tell?
I’d thought it was because we have 2 lungs, and one nostril usually gets stuffed.
Your nostrils open into your throat. Well before your lungs.
I think your onto something about one being stuffed though.
:dubious: sniff
Nah. I’m just a hobbiest. But thanks 