Re: How many dinosaur species survived the KT event?

Walter Bushell wrote:

In article <%QXLg.21972$kO3.12244@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
John Harshman <jharshman.diespamdie@xxxxxxxxxxx> wrote:


Walter Bushell wrote:


In article <1hlaheu.18w3ma4qjjgfcN%j.wilkins1@xxxxxxxxx>,
j.wilkins1@xxxxxxxxx (John Wilkins) wrote:



Walter Bushell <proto@xxxxxxxxx> wrote:



In article <KdoLg.8238$yO7.5567@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
John Harshman <jharshman.diespamdie@xxxxxxxxxxx> wrote:



UC wrote:



John Harshman wrote:



UC wrote:




Ken Denny wrote:




Are all birds descendants of a single dinosaur species that lived at
the time of the KT event?


Yes.





Or multiple species?


Yes, that too.

That makes no sense at all. The alternatives are mutually exclusive.




Did one species maybe
evolve into ostriches, emus, etc. another into penguins, and another
into all the other bird species?


Yes, three.

That makes even less sense.

Or was nonsense your goal?


Si.


So hard to tell, since most of what you say is nonsense, even when you
(apparently) aren't intending it.

Eukaryotes are the best prokaryotes.

ITYM eukaryotes are the best karyotes.


Eukaryotes make the best carryouts.

But I thought prokaryotes were all the life forms that weren't
eukaryotes.

according to

http://www.earthlife.net/cells.html

All living things are divided into two major groups depending on how
their cells are set up, these two groups are the Prokaryotes, and the
Eukaryotes.


Thus the eukaryotes must have descended from prokaryotes, hence
eukaryotes must be prokaryotes. It would be hard to explain how a
eukaryote could emerge, except from a simpler cell, which would have to
be a prokaryote.


Not necessarily true. Some groups are not clades, with membership
criteria based on descent, but are classes, with membership criteria
based on possession of particular characters. And this is true for
prokaryotes. They're like the everyday definition of "fish", which means
more or less "vertebrates that live in the water and have gills and
fins". We are not prokaryotes because we don't possess the defining
characters of prokaryotes.

Now of course eukaryotes have several ancestors, some of which (the
ancestor of mitochondria, for example) were clearly prokaryotes.


I was under the impression that some eukaryotes did not have
mitochondria, just like some do not have chloroplasts.

This is true, but it's far from clear whether any of them are
primitively so. Most, perhaps all, seem to have had mitochondria at one
time and have lost them.

Anyway among the
non eukaryotes descent is a murky concept.


It's
not clear whether all of them were. At this point we get into the fact
that prokaryoteness (prokaryotude? prokaryotidity?) is defined on the
basis of several characters that might not have always gone together,
and some of which are not quite discrete. There are now two sizes of
ribosomes, but what would you call a cell with intermediate-sized
ribosomes? Where did nuclear membranes come from? Was it originally a
cell membrane of yet another eukaryote component?

So the cladistic idea of prokaryotes has two big problems. First, it
goes against the common definition. This is not a really big problem,
since words can always be redefined if we find them useful, as with
other groups that were formerly paraphyletic.

It's difficult when popular usage has been established for a long time
in a widespread fashion, which results in scientists using the same word
differently from the public. We have seen the trouble this creates.

For the most part, that trouble exists in UC's mind. Any other trouble
is minor. Unless you want to provide an example?

However, if we redefine
"prokaryote" cladistically, it would appear to be a junior synonym for
"life". Second, the concept of cladistic definitions gets into trouble
if the group in question is massively reticulate, and even if we ignore
the various organelles, the eukaryote nucleus may have been assembled
from multiple sources.

As you may have guessed, I was pushing the cladist idea to it's limit,
to see how if it broke and how. In the case of "Birds are dinos", I
suppose it depends on what the meaning of "is" is.

I don't see that it does. It depends on whether you want to use a
cladistic meaning of "dino". Usually, it seems better to do so,
especially when the context is at all scientific, as we might hope it is
on TO.

.

Relevant Pages

  • Article: Is the Term Prokaryote Obsolete?
    ... Such proposals have sustained the concept that prokaryotes ... evolved into eukaryotes -- an evolutionary model invoked by the terms ... first of ribosomal RNA genes in the late ... Comparisons of ribosomal RNA sequences show a three-domain tree of life. ...
    (sci.bio.evolution)
  • Re: How many dinosaur species survived the KT event?
    ... Eukaryotes are the best prokaryotes. ... ITYM eukaryotes are the best karyotes. ... eukaryote could emerge, except from a simpler cell, which would have to ... based on possession of particular characters. ...
    (talk.origins)
  • Re: How many dinosaur species survived the KT event?
    ... Eukaryotes are the best prokaryotes. ... ITYM eukaryotes are the best karyotes. ... eukaryote could emerge, except from a simpler cell, which would have to ... based on possession of particular characters. ...
    (talk.origins)
  • Re: Why did eukaryotes evolve?
    ... > from prokaryotes, with whose reproductive efficiency eukaryotes can't ... Eukaryotes seem to be a lot more successful as social organisms than ... rapidly-reproducing organisms. ...
    (sci.bio.evolution)
  • The origin of eukaryote life
    ... Unlike prokaryotes, eukaryote organelles are arranged ... within the cell in highly determined spatial patterns. ...
    (talk.origins)