Re: Bizarre Newsnight Story About England Flags and Racial Hatred



George wrote:

"Deirdre Sholto Douglas" <finch.enteract@xxxxxxx> wrote in message
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George wrote:

"Madra Dubh" <ccaine@xxxxxxxxxxxxxxxx> wrote in message
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"George" <george@xxxxxxxxxxxxxxx> wrote in message
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I'm not so sure. There appears to be a lot of different species
laying
low in the La Brea tar pits. As for destroying the planet, that is
always a possibility, though we are hardly the first and only species
to
alter the planet. With the advent of cyanobacteria, the earths'
atmosphere changed from one composed of Nitrogen, carbon dioxide, and
methane, to one where nitrogen and oxygen are the major constituents.
Because oxygen is a corrosive and a poison to many species that
existed
at the time, that major change in the composition of the atmosphere
let
to one of the first, if not the first mass extinction on the planet.
Of
course, it also led to the rise of most species that exist today,
including us.

Still, most of the mass extinctions I'm familiar with came about
through
natural causes.
Man, OTOH..............

Well, origin of species (cyanobacteria) is about as natural as it gets.

Cyanophytes are unlikely to be the origin of species
as they were one of the _last_ prokaryote forms to
develop. Chemoautotrophs hit the scene before photo-
trophs and it's likely the first cells were more closely
aligned with modern archaeans than cyanophyta.

Deirdre

Umm, it was a metaphor, Deirdre. I wasn't suggesting that they were the
first lifeform on the planet (obviously they weren't if they were churning
out oxygen, poisoning the oceans and atmosphere with it, and killing other
lifeforms - the ones that already existed - in the process), but that they
were the lifeforms that ultimately led to mammals and humans.

It was a bad one, George, science is not metaphorical.

Additionally, they _didn't_ kill off the "other life forms"
by "poisoning the atmosphere" because at the time they
arose, there were no land based lifeforms _to_ kill off.

They also didn't "poison" the oceans...the only other or-
ganisms about when the cyanos were doing their thing
were chemoautotrophs which live in a completely differ-
ent (anaerobic) environment. The ones in the benthic
zone had no problems whatsoever because it _stayed_
anaerobic and those which had been up top in the eu-
photic zone (when it was also anaerobic) simply went
down in the water column and found a happier spot to
reside on the other side of the redox cline...light isn't
an issue if lunch is a sulphur molecule.

In fact there are even bacteria today with their own
magnetic compasses so they can _find_ their side of
the redox cline...if you're a bug in the ocean, magnetic
north is always _down_.

The light dependent cyanos were up euphotic zone and
since dissolved oxygen in the water column is directly
correlated to temperature (generally forming a clino-
grade curve) and since, dissolved O2 or no, it wasn't
getting any warmer down there, it's unlikely that diffu-
sion was occurring at a rate where it had any impact
on a bacterium motile enough to swim away.

Additionally, the organic wastes associated with the
photosynthetic reaction _sink_...even cyanophyta
curl up their (figurative) toes eventually. This means
that the CO2 at the bottom is _increased_ and the
reaction at the bottom is reversed to _favour_ res-
piration. Moreover, it's been demonstrated that
cyanobacterial exudates have a _synergistic_ affect
bacterial communities with the increase in organic
carbon resulting in an increase in biomass production.

It wasn't the "death" of anything, it was more like
the Golden Age of facultative dissimilatory reducers.
And they _didn't_ lead to mammals or humans...your
bacterial ancestors were heterotrophs, which most
likely arose from the chemoautotrophs, _not_ photo-
autotrophs...you don't photosynthesise, do you?

Stick to rocks, George, leave the bugs to others.

Deirdre
.

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