Human physiology?!


Question:
Why do we have two eyes?

Why do we have two ears?

Why do we have two nostrils?
Answers:
ask Darwin

Other Answers:
Two eyes and two ears-- Having one for a back up. Two eyes gives 3 dimentional viewing.
As for 2 nosterals, not sure.

EYES



MadSci Network: Evolution

http://www.madsci.org/posts/archives/feb99/920061344.Ev.r.html



Re: Why do all fish, mammals, reptiles and birds have exactly two eyes?



"In summary, animals that have two eyes have them because of two

reasons. All vertebrates with eyes have two because the common

ancestor of vertebrates had two eyes. That common ancestor had two

eyes for the same reasons that invertebrates with eyes tend to have

only two complex eyes: two eyes are better than one because they allow

comparison of light coming from two directions, while a third eye

doesn't give enough extra information to make it worth the costs of

having it."EARS



Two Ears Are Better Than One

http://www.starkey.co.uk/pages/learn/learnHearing2.html



Why do we have two ears? Much like having two eyes helps us to see all

around us, having two ears helps us locate sound in time and space.



Balanced or binaural hearing is vital to your ability to locate where

a sound is coming from. The brain instinctively locates a sound’s

source by measuring the tiny differences in duration and intensity in

the way each ear hears the sound.



*****



"Q: Why do we have two ears?

Http://freda.auyeung.net/5sens.



A: We have two ears because the sounds hits one ear a fraction of a

second before the other and produces stronger vibrations. It helps

you tell what direction the sounds come from."NOSTRILS



MadSci Network: Development

http://www.madsci.org/posts/archives/jan2000/947001218.Dv.q.html



"Question: Why do humans have two nostrils?



Is there any particular reason/advantage in having two nostrils? What

would happen if someone only had one nostril?"



Answer:

http://www.madsci.org/posts/archives/jan2000/947001218.Dv.r.html



"Why do humans have two nostrils?


Most animals, including humans, are bilaterally symmetrical. This means

that the right and left sides are mirror images of one another. Thus both

sides develop somewhat independently of each other. Having said that I have

to emphasize the word "somewhat," since there is a great deal of

interrelationship, interaction, and communication between the two sides

for normal development to occur. Thus, as the face develops, two nasal

placodes (thickenings of the frontal process) develop. These begin to

submerge and as they do, each placode results in the formation of a nasal

chamber, and the region surrounding each placode forms a horseshoe-shaped

thickening, known as the nasal process. Each nasal process is subdivided

into a lateral and a medial nasal process, which partially surround the

opening into nasal chamber. Since it is a horseshoe-shaped structure, it

will require a closure at its open end and that closure results from the

fusion of the lateral and medial nasal processes with the developing

maxillary process."
Answers:

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