Xref: utzoo sci.bio:1947 talk.origins:4661
Path: utzoo!attcan!uunet!lll-winken!spl1!ddsw1!corpane!sparks
From: sparks@corpane.UUCP (John Sparks)
Newsgroups: sci.bio,talk.origins
Subject: Re: The birds and the beaks
Summary: Why don't bats have beaks?
Keywords: evolution, birds, beaks
Message-ID: <464@corpane.UUCP>
Date: 20 Mar 89 23:00:37 GMT
References: <404@censor.UUCP> <27216@apple.Apple.COM>
Organization: Corpane Industries, Inc., Louisville Ky
Lines: 46

In article <27216@apple.Apple.COM>, sabol@Apple.COM (Bryan Sabol) writes:
]    To be able to fly, ancestral birds needed to modify existing
] structures to lighten their bodies, yet retain similar function with
] these adaptations.
] ...
]    The beak was a sophisticated modification that enabled birds to
] rid themselves of the great amount of weight which is associated with
] teeth and their supporting structures.
] [explanation about support structure needed to have teeth. ]
] [cranial ridges, jaws, jaw muscles etc  -deleted for space ]
] 
]    So, if an animal wanted to considerablely lessen its total mass
] without losing the function of said massive structures, a beak would be
] a particularly good development.  Beaks are strong, light, and weigh
] very little.  The one thing they can't do is chew food, so the addition
] of a few pebbles, etc., to a gizzard does the job.  The beak made the
] large jaw, and the large bones which support the muscles to operate the
] jaw, unnecessary. 
] 
]    Finally, I would argue against your friend's theory of beaks
] developing because of no front limbs (or, at least, modified into
] wings).  If this were true, then we could expect to see snakes with
] beaks.  Or maybe some bats would, too (since the snake has no front
] limbs, and the bat has wings).

Your arguement seems to break up for me here. You use the fact that snakes
and bats don't have front limbs and no beaks, to show that birds did not
develop beaks just because they don't have front limbs (just wings). What
does one have to do with the other? Snakes and bats aren't birds. Different
animals have evolved differently from the same stimuli.

If all animals evolved simularly from the same environmental pressures, I could
use your arguement to ask you then, since bats and some birds both have wings
and eat the same diet, why don't bats have beaks? Don't they have
to save weight? Why do they have teeth? Jaws and such? Why do penguins have
beaks? They can't fly. So no need to save weight there. Do penguins have teeth?
I believe they do. What is the air speed velocity of a swallow?

Enquiring minds want to know!!!


-- 
John Sparks   |  {rutgers|uunet}!ukma!corpane!sparks  | D.I.S.K. 24hrs 1200bps
______________|          sparks@corpane.UUCP          | 502/968-5401 thru -5406
 
If we weren't supposed to juggle, tennis balls wouldn't come three to a can.