Hi titromua,
Thank you for a very interesting question. :)
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."
*****
Does an objective look at the human eye show evidence of creation?
http://www.2think.org/eye.shtml
"Biologist George Williams wrote an entire book on the subject of
design and purpose in nature. Near the beginning of The Pony Fish's
Glow, Williams responds to Paley's watchmaker argument using various
body parts as examples of why Paley's argument may look good on the
surface, but it lacks credibility when closely examined using modern
technology and biology. Here he discusses the human eye:
"not all features of the human eye make functional sense. Some are
arbitrary. To begin at the grossest level, is there a good functional
reason for having two eyes? Why not one or three or some other number?
Yes, there is a reason: two is better than one because they permit
stereoscopic vision and the gathering of three-dimensional information
about the environment. But three would be better still. We could have
our stereoscopic view of what lies ahead plus another eye to warn us
of what might be sneaking up behind."
*****
Sight Sense
http://freda.auyeung.net/5senses/see.htm
"Q: Why do we have two eyes?
A: We have two eyes because having two eyes increases your angle of
vision. It helps you to judge depth. Having two eyes allows us to
see 180 degrees and three-dimensional objects."
=========
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/5senses/hear.htm
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."
*****
Hearing Health
http://www.drf.org/hearing_health/Archive/2003/spr03_aretwoearsbetter_ex.htm
Are Two Ears Better Than One?
"Why do we have two ears anyway? According to the Roman philosopher
Epictetus, ?We have two ears and one mouth so that we can listen twice
as much as we speak.?"
[edit]
"Among the advantages of having input from both ears is the ability of
the one nearest to a stimulus to pick up and focus on that specific
sound rather than others. This is known as the ?better ear? effect.
Another benefit of having input from both ears is that specialized
neurons in the auditory pathway are sensitive to cues that help us
identify the location of a sound source, a phenomenon called binaural
hearing. These important cues include differences between the two ears
in the arrival time and intensity of sounds from various directions.
For instance, a sound that arrives from the right will reach the right
ear first and have greater intensity in the right than the left ear.
The reverse is true for sounds arriving from the left."
*****
MEI.com
http://www.michiganear.com/library/H/hearingaidtext.html
"We have two ears for many reasons. Two ears help us to hear from all
sides, not just from one restricted area. Two ears help us hear speech
in noise situations like restaurants or parties with lots of people
talking. Our brain must compare the information from different angles
to help filter the unwanted sounds from those we need to hear. Two
ears help us hear those quiet sounds. This is very important when we
need some amplification but not too much amplification. Many loud
sounds can be very loud and this is even more striking for many
indivinuals with a hearing loss."
=========
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."
*****
Smelling roses: Your nostrils may part ways
http://news-service.stanford.edu/news/1999/november10/smell-1110.html
"Michael Leon, a professor of neurobiology and behavior at the
University of California at Irvine said the Nature article "describes
a wonderfully clever piece of work that answers a question that nobody
had even thought to ask. That is, why do we have two nostrils?" The
data suggest, he said, that the olfactory system maximizes the ability
of its distributed receptor neurons to encode differentially absorbing
odors.
The difference in perception of the nostrils is very subtle and
probably cannot be noticed by most people most of the time, Sobel
said. The world is made up of complex, smelly things, such as a rose
that may consist of countless odor components. To establish that there
was a difference between the nostrils, the researchers mixed equal
amounts of two chemicals whose odors sorb at different rates --
octane, which smells similar to anise, and l-carvone, which smells
like peppermint."
=========
Great Moments in Science:
http://www.abc.net.au/science/k2/moments/s198395.htm
Nostrils smell differently
"We have two eyes on the front of our heads. Each eye gets a slightly
different picture of the world, and this stereo image gives us the
impression of depth. Our two ears pick up sounds at slightly different
times, and this lets us work out where the noise is coming from. And
it now turns out, that each of our two nostrils can pick up different
smells."
=========
http://www.metanexus.net/metanexus_online/show_article.asp?5789
"Well, any alien arriving on the planet Earth might be struck by the
obvious bilateral symmetry of its creatures. Two eyes, two ears, two
nostrils, two legs, two lungs...but, wait, what about the heart? Not
to mention the entir= e [sic] digestive system. It would seem that in
the biological realm, as the needs change, so do the rules. Bilateral
symmetry is only a rule as long as bilateral symmetry is useful."
=========
Keyword search:
Why do humans have two eyes
Why do humans have two ears
Why do humans have two nostrils
Best regards,
tlspiegel |
