About the chicken and egg issue, this has been solved satisfactoraly:
The chicken which has hatched from the egg has the same genotype as the
egg. The individual which laid the egg did not have the same genotype as
the egg, i.e. the bird which laid the egg was nearly a chicken. So, the egg
came first.
Gijs
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> Van: Kay Lavalier <[log in to unmask]>
> Aan: [log in to unmask]
> Onderwerp: Re: Scavengers
> Datum: vrijdag 31 maart 2000 0:58
>
> Andrew Vik
> [log in to unmask]
>
> Dear Nora and Paulino:
>
> I guess this is one of those "which came first, the Chicken or the Egg"
type
> discussions.
> The best answers still amount to educated speculation. Most predators
will resort to
> scavenging in the right situation, and some seem to prefer it
(opportunistic
> scavengers). The number of animal species that eat only carrion (true
scavengers) is
> quite small when compared with the part time scavengers. Here are some
examples of
> full time scavengers which originated from predatory ancestors. The
Vultures and
> Condors (Aves, Cathartidae) are specialized raptors. The Slime Hags
(Agnatha,
> Myxinoidea) are jaw less fishes that consume a carcass from the inside
out. I can
> think of no examples of predators that evolved from full time scavengers.
That is one
> of the reasons why some paleontologists theorize that the highly
specialized
> Tyrannosaurus (its forelimbs were quite useless) was a carrion fancier.
>
> True, our human chauvinism is what makes us take more interest in
predators than the
> more highly specialized scavengers and parasites. We are predators
ourselves. But even
> humans will resort to scavenging and even cannibalism in hard times.
>
> I'll now try to bring this thread back in line with our subject,
Malacology.
> Does anyone know of any molluscs that are full time scavengers?
>
> Yours, Andrew
>
> NORA BRYAN wrote:
>
> > We were discussing this issue again last night and were thinking about
the raging
> > T-Rex controversy - was T-Rex a predator or a scavenger? We'll never
know for
> > sure, but some people go to great lengths to 'prove' that they were
predators -
> > i.e. they are more noble creatures being predators, and have better
box-office
> > billing. Jurassic Park would not have been so thrilling for audiences
if T-Rex
> > was poking through garbage dumps for tasty morsels!
> > I think most so-called predators and scavengers are opportunistic
feeders anyway -
> > meat is meat, although some animals like most cats disdain old meat.
> > In George Schaller's famous book about lions, he showed that different
prides have
> > different habits but that many lion prides got a good portion of their
meat by
> > driving hyenas off their kills. This shocks some people because after
all lions
> > are noble animals and hyenas are scavengers - right???
> >
> > Kay Lavalier wrote:
> >
> > > Andrew Vik
> > > [log in to unmask]
> > >
> > > Dear Nora:
> > >
> > > I agree with you 100%. Scavengers do a very important job on this
planet. They
> > > just aren't as exciting as predators are. But we must realize, most
scavengers
> > > have evolved from predators, not the other way around. I do not
believe in
> > > de-evolution, the idea that life forms can regress to a more
primitive state.
> > > Therefore, scavengers could be thought of as an improved predators.
> > >
> > > Yours, Andrew
> > >
> > > NORA BRYAN wrote:
> > >
> > > > Andrew
> > > > Interesting choice of phrase - "defaming". It's odd how we tend
to think
> > > > of scavengers as somehow less worthy of our admiration. I guess
it's a
> > > > natural reaction (maybe we picture ourselves eating roadkill and
get a
> > > > little grossed out at the idea!). Of course we know logically
that
> > > > scavengers are an extremely important part of the natural cycle.
Sometimes
> > > > when I see a dead animal I feel sad, but then I feel better when I
see the
> > > > various birds and animals making use of the carcass to feed
themselves and
> > > > their young. Death feeds life.
> > > >
> > > > Nora
> > > > Calgary, Alberta
> > > > CANADA
> > > >
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