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Re:Re:avian flight



<<A living being has a certain way
of life, a mutation appears, this way of life provides selectionary pressure
too keep this mutation, and afterwards the mutation is called an adaptation.
And adaptations like wing feathers (or limbs, for that matter, in the origin
of tetrapods) can be exapted for use in other ways of life.>>
The  mutation happens----> the caracter(s) that that are the espression of the genetic mutation are under a selective pressure(with the whole animal bearing it) and if this mutations gives some advantages to the animal, against other animal of the same species,( and in general against all the "forces" that will deny it survivaland thus reproduction ) with the "old" caracter(given the possibility of  the permanence of the same  enviromental conditions for some generations), then it will probably become the most present "version" in the population;
 
you wrote., <<this way of life provides selectionary pressure
too keep this mutation>>I don't understand what you mean by "selctionary pressure to keep this mutation"
the selective pressure is on, the mutation, meaning( i know  i write not very well, i'm sorry; hope you understand what i mean) that it's not acting to keep it( it sounds like "trying to preserve the mutation"), but against it.
 
<<Dippers hunt aquatic insect larvae.>>
ok
 
<<Remember the tail of *Archaeopteryx* that prevented it from gliding? >>
 Mr Cunningham answer to this...
 
<<Prey in
the mouth would have pulled the center of gravity forward and thus made
flight easier. >>
 
has someone tried to quantify this "easier"?
 
 
<<Well, then, why has flight only evolved three times among vertebrates and
not three hundred times? Or, on the other hand, much earlier?>>
 
maybe because the phisical features (not the same in the three cases, surely) needed to be able to get in the air evolved  rarely; and , however, i don't think it's sufficent to have these features: contingence has  its role, an important one.
 
<< in the air above
small ones, there are the same insects as on the dry land around.>>
Infact I said that , given the possible use of this scenario( an aquatic theropod trying to get something in the air from the water surface) as one of the reasons that possibly led to the evolution of flight, it would be nothing different from the scenario imagined as a support to the ground-up theory.
 
Have you ever talked about large masses of whater?
 
 
<<if you can detect one in the hypothesis
I presented... and if I can't "discuss it away"...>>
 
I think the dynamic ones and the others regarding the possible reasons for the evolution of flight from swimming theropods are quite correct and you haven't demonstrated that I'm wrong in my observations (because no studies have been done, surely....).
 
<<The wild form of the domestic chicken that lives somewhere in South East
Asian jungles doesn't fly more.>>
what are their predators?
 
 
<<I'm quite sure predator pressure hasn't changed much since the Permian or
so. Why should it have?>>
maybe i told badly what i wanted to say, because this answer doesn't make much sense to me.
 
the predator pressure is sctrictly related to the particular habitat you look at; it depends on what kind of predators are present, how many different kinds and so on; predatory animals have changed a lot from permian times so i don't really understand what you mean.
Big flightless birds evolved in australiaand other isolated(big or small) enviroments because of the absence of big predators..you know how the story ended.
 
<<You know, ostriches and rheas have evolved flightlessness in environments
that were always full of predators>>
I'd like to know something more about this, if possible.
since I've always thought big flightless birds evolved in relatively "hunterpoor" enviroments...
 
however do you want to compare the running abilities of chickens and ostriches?
 
"In a jungle, hiding from predators is very easy."
 
oversimplifying...
predators can hide as well....
 
<<But this doesn't explain in any way *how* "the features
needed to get in[to] the air" *evolved*, >>
 
infact..
 
<<I'm the one who has probably written the longest post in the history
of this list. :-]>>
 
we will probably end up writing very much indeed;-)
..it would be even more if someone else wanted to join the discussion....=)