Re: Evolution and other planets

From: Malcolm (malcolm_at_55bank.freeserve.co.uk)
Date: 12/27/04 

Date: Mon, 27 Dec 2004 04:13:10 +0000 (UTC)

"Perkowski" <perkowski1@optonline.net> wrote
>
> If life can possibly exist on other planets that are similiar to Earth,
> what are the chances of animal and plant life on those planets following
> the animal and planet life here on Earth?
>
> For example, could a planet somewhere in our galaxy be the home
> of past creatures like the dinosaurs that appeared here on Earth?
>
> All things being equal, would animals/plants on other world follow
> the same evolutionary map that animals/plants on Earth do?
>
The problem is that we don't have another example of a life-bearing planet.
So any answer must be highly speculative.

Organisms on earth are dividied into prokaryotes (bacteria) and eukaryotes.
Eukaryotic cells are much more complex, and seem to have formed from several
cells living symbiotically.

One of the features of eukaryotic cells is that they contain mitochondria,
which produce ATP, which is used by all cells on Earth as their primary
energy source.

Now it is hard to believe that cells from other planets would also contain
mitochondria. It is easier to believe that they would use ATP as energy
currency, but even that is difficult to determine.

All multicelular organisms on Earth are eukaryotes. It is not really
understood why that should be, and some bacteria do appear to have a certain
amount of social life, and be partway to multicellularity. Until we
understand what it is about eukaryotes that leads to many of them becoming
mutlicellular organisms, we cannot really give an answer concerning the
possibility of mutlicellular life on othe planets. It may be common, it may
be extremely rare, it may be that some other system that is analogous to
neither multi-celled nor single-celled terrestrial organisms is in fact the
norm.

As for whether the animals would look anything like vertebrates, almost
certainly not. Science fiction movies you see with aliens like lizards,
clutching laser guns that look more or less like modern assualt rifles, are
showing a serious lack of imagination.

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