Bertvan has a fantasy:
>T: Good morning, students, this is a biology class, where we study biology,
>and nothing but biology. Evolution is an important part of biology.
>
>ST: What is evolution?
>T: Evolution is what scientists say it is.
Evolution is a change in the gene frequency of a population over time
>St: Do you mean how random mutation and natural selection turned reptiles
>into birds?
>
>T: Hmmm.
Yes, absolutely. Take for example archaeopterix (I'm quoting from Lenny
Flank's website here. He has a Ph.D. in biology and I don't. Sorry for the
length. As Christ pointed out in another post evolution does not break down
easily into sound bytes.)
One almost could not ask for a better example of a transitional fossil than
Archaeopteryx. It exhibits
an unmistakeable mixture of reptilian and avian characteristics. A bird, of
course, is defined by the
presence of feathers. Flight feathers of Archaeopteryx are well-preserved,
and are virtually
indistinguishable from those of modern birds. They possess the central
shaft and side barbules found
in any songbird of today. The feathers are also asymmetrical and are wider
on the trailing edge than
the front edge--an adaptation shown by flying birds but not by flightless
birds such as penguins or
ostriches. This indicates that Archaeopteryx was probably capable of flight
(although the fossil lacks
the large keeled breastbone which all modern birds use to attach their
flight muscles, and the
attachment points were themselves much smaller than in modern birds--thus
it is possible that
Archaeopteryx was only a glider and was not capable of powered flight). The
large contour feathers
are the only kind found on Archaeopteryx skeletons--no smaller downy
feathers have been found,
although these are possessed by all modern birds.
Apart from the feathers, however, Archaeopteryx exhibits a number of
characteristics which are
not birdlike at all, but are shared by the therapod dinosaurs--and some of
these are found in no
other group of animals. Among the dinosaurian characteristics exhibited by
Archaeopteryx are:
simple concave articulation points on the cervical vertebrae, rather than
the elongated
saddle-shaped articulation found in birds; vertebrae in the trunk region
which are free and mobile,
rather than fused together as in birds; the presence of gastralia, or
abdominal ribs, which are found
in reptiles and therapods but not in birds; a rib cage which lacks uncinate
processes and does not
articulate with the sternum, rather than the strutlike uncinates and
sternum articulations found in
all birds; a sacrum consisting of only 6 vertebrae, rather than the 11-23
found in birds; mobile
joints in the bones of the elbow, wrist and fingers, rather than the fused
joints found in birds; a
shoulder socket that faces downward like a therapod's, rather than outward
like a bird's; solid bones
which lack pneumatic sacs, rather than the hollow air-permeated bones found
in birds; and a long
bony tail with free vertebrae, rather than the short fused pygostile found
in birds;
The Archaeopteryx skull is also typically reptilian in structure,
exhibiting: a number of openings or
"fenestrae" in the skull, arranged as in therapod dinosaurs and not birds;
a heavy but short
quadratic bone which is inclined forward as in reptiles; a bend in the
jawbones behind the tooth row;
a long retro-articular process, which is found in reptiles but not in
birds; a thin straight jugal bone as
in reptiles; a preorbital bar separating the anteorbital fenestra and the
eye socket (a reptilian
characteristic); an occipital condyle and foramen magnum that are located
above the dorsal end of
the quadrate bone as in therapods, rather than below the quadrate as in all
other birds; and a brain
structure which exhibits elongated and slender cerebral hemispheres which
do not overlap the
midbrain (in birds, the cerebral hemispheres are heavy and extend over top
of the midbrain).
There are also some features present in Archaeopteryx which are present in
primitive form in the
therapods but in more advanced form in the birds. In the therapods, for
instance, the hallux, or big
toe, is located on the back of the foot and forms a short claw that doesn't
reach the ground. In birds,
this toe is greatly elongated and is used for perching. In Archaeopteryx,
the hallux is reversed, but is
elongated to an extent midway between the therapods and the birds. In
therapods, the fingers of the
front arms are long; in birds, the fingers are reduced to tiny nubbins.
Archaeopteryx is midway
between these conditions, In birds, the wings are supported by the furcula,
or wishbone, which is
composed of the two fused clavicles, and Archaeopteryx also possesses a
fused furcula (though not as
strong as that in modern birds). A few of the therapods had clavicles,
including such birdlike species
as Velociraptor. And a therapod species known as Oviraptor is believed to
have possessed a fused
furcula, as in birds.
It is thus apparent that Archaeopteryx, although it possessed feathers and
must therefore be
considered to be a bird, nevertheless demonstrated many more
characteristics which were unique
to therapod reptiles, and must be viewed as an evolutionary transitional
from therapod dinosaur to
birds.
>St: My cousin Abby says some scientists don't believe random mutation and
>natural selection turned reptiles into birds.
>
>T: All reputable scientists believe it. Your cousin Abby is an ignorant liar.
The cousin is certainly ignorant of the facts. Mutation and natural
selection have been observed to occur in the wild and in the laboratory and
all scientists know this even the ones who deny it for religious reasons.
Cousin Abby should read up a bit.
>St: She said one of the scientists who doesn't believe it is Sir Fred Hoyle.
>Has he become disreputable?
>
>T: Hoyle is an astronomer. No one is allowed thoughts about evolution except
>biologists.
as far as biology is concerned Hoyle is disreputable. He believes that
insects have superhuman intelligence and are concealing it from us. He also
believes that aliens caused evolution.
>St: I've heard there are even biologists who don't believe it.
don't believe what? In natural selection? Don't believe the evidence of
their eyes? Don't believe in "macro" evolution? Don't believe in what?
>T: Yes, well, as your cousin knows, the supreme court does not allow such
>talk in a biology classroom. To continue, evolution complicated, and no one
>but biologists completely understand it. However evolution is what
>evolutionary biologists say it is, and we are not here to discuss it. My job
>is to explain to you that evolution is TRUE.
the teacher's job is to explain evolution.
>St: What about those scientists who believe the universe is the result of a
>rational design?
>
>(student from back of classroom): He said "design", teacher! I heard him!
>That's practically the same as saying G--. I'm going to tell my cousin in
>the ACLU that someone practically said the G-word in the classroom!!!
ROFL!!!! The teacher is not allowed to teach religion (ID) in the
classroom, but, of course, the students can say anything they like. The
ACLU is worried about people using the force of government to teach the
religious views of one of the many religions in the U.S. The student, of
course, does not have the force of government behind him or her as the
teacher does.
etc. :-)
Susan
----------
The most important human endeavor is the striving for morality in our
actions. Our inner balance and even our very existence depend on it. Only
morality in our actions can give beauty and dignity to life.
--Albert Einstein
http://www.telepath.com/susanb/
This archive was generated by hypermail 2b29 : Wed Aug 09 2000 - 12:52:21 EDT