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  • From: Lawrence London <lfljvenaura@gmail.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: [permaculture] How chemistry affects the evolution of life (SciLog article and YouTube video)
  • Date: Sat, 21 Mar 2015 15:36:33 -0400

Article:
http://www.scilogs.com/maniraptora/how-chemistry-affects-the-evolution-of-life/
How chemistry affects the evolution of life
20 March 2015 by GrrlScientist, posted in Chemistry, Evolution, Journal club
Video:
Science Stories - Adaptability
https://www.youtube.com/watch?feature=player_embedded&amp;v=xqXawm9m9Gg
This film is part of a series of science stories that celebrate 350 years
of scientific publishing by the Royal Society.

SUMMARY: In this fascinating video, Professor Ros Rickaby from Oxford chats
with Professor Simon Conway-Morris at Cambridge about how Earth’s changing
chemistry has affected evolution, and how this can sometimes lead to
evolutionary convergence

A feature of natural selection, or “survival of the fittest”, is that
context defines what is “fittest”. Traits that are “fittest” in one habitat
can become liabilities in others. This was observed first-hand across
Britain when it was newly industrialising: wing colour of the peppered
moth, Biston betularia, changed from pale grey with darker spots to dark
charcoal. This was due to the effects of predation by birds, who suddenly
could easily spot pale-winged peppered moths dozing on soot-covered tree
trunks by day (doi:10.1098/rsbl.2011.1136). Most of the peppered moths that
survived long enough to reproduce had charcoal-coloured wings, a trait that
they passed on to the next generation. Thus, within the context of sooty
trees and hungry birds, a trait that was previously “fittest” became a
liability.

Likewise, where natural selection occurs at the molecular level, it can
only occur within the context of the chemistry that is available at that
time (doi:10.1098/rspb.1981.0071). When a major revolution occurs in the
chemistry, that could lead to significant innovations in the evolution of
life itself. For example, we know that in the absence of atmospheric
oxygen, a variety of important elements, such as copper and zinc, were
inaccessible to life. Those elements may have played a key role in
promoting multicellularity, which is a major step in the evolution of life.

“There seems to be a way that the chemistry [of these elements] is almost
informing or feeding back onto these major evolutionary steps so we can
trace chemical evolution by peering into the genome”, said biogeochemist
Ros Rickaby, a professor in the Department of Earth Sciences at the
University of Oxford.

“One idea that I had was to try and look into the genome of RuBisCO to see
if we can see times where changing carbon dioxide has affected the working
of this enzyme”, said Professor Rickaby.

RuBisCO -- the shortened and more easily pronounced version of its formal
name, ribulose-1,5-bisphosphate carboxylase/oxygenase -- is far and away
the most abundant protein on the planet (doi:10.1073/pnas.0400981101). It
catalyses the pivotal step in photosynthesis by harnessing the energy in
sunlight to convert atmospheric carbon dioxide into the sugars that fuel
and support life on Earth. This chemical process is known as carbon
fixation.

But as enzymes go, RuBisCO is surprisingly inefficient. It is slow and
easily distracted by oxygen when the concentration of carbon dioxide is
low. Like that car filled with rubberneckers that slows all traffic to a
crawl on a narrow road, the plodding RuBisCO is the rate-limiting step of
photosynthesis. Nevertheless, after a million years of so of work, RuBisCO
eventually lowered atmospheric concentrations of carbon dioxide and
increased oxygen, and this, in turn, diminished its already sluggish
performance.

To solve that problem, a second enzyme, carbonic anhydrase, popped up. It
works alongside RuBisCO to raise the local concentration of carbon dioxide,
thereby allowing RuBisCO to work faster and more efficiently. Compared to
the lackadaisical RuBisCO, carbonic anhydrase is the speediest enzyme known.

In stark contrast to RuBisCO, which is both functionally and structurally
unique, carbonic anhydrase is a huge family of enzymes comprised of five
distinct groups that share almost no molecular or structural similarities
-- except they all use a zinc ion to catalyse the same chemical reactions.
Thus, carbonic anhydrase is one of the best examples of functionally
related enzymes that arose from as many as five very different starting
points in the Tree of Life before converging onto the same chemistry.

In this fascinating video, Professor Rickaby chats with paleobiologist
Simon Conway-Morris, a professor in the Department of Earth Sciences at the
University of Cambridge, about how Earth’s changing chemistry has affected
evolution, and how this can sometimes lead to evolutionary convergence:

Science Stories - Adaptability
https://www.youtube.com/watch?feature=player_embedded&amp;v=xqXawm9m9Gg
This film is part of a series of science stories that celebrate 350 years
of scientific publishing by the Royal Society. You can find The Royal
Society on twitter @RoyalSociety and Royal Society Publishing is also on
twitter @RSocPublishing

Sources:

Williams R.J.P. (1981). The Bakerian Lecture, 1981: Natural Selection of
the Chemical Elements, Proceedings of the Royal Society B: Biological
Sciences, 213 (1193) 361-397. doi:10.1098/rspb.1981.0071

Cook L.M., I. J. Saccheri & J. Mallet (2012). Selective bird predation on
the peppered moth: the last experiment of Michael Majerus, Biology Letters,
8 (4) 609-612. doi:10.1098/rsbl.2011.1136

Amit Dhingra, Archie R. Portis, Jr., and Henry Daniell (2004). Enhanced
translation of a chloroplast-expressed RbcS gene restores small subunit
levels and photosynthesis in nuclear RbcS antisense plants, Proceedings of
the National Academy of Sciences, 101 (16) 6315-6320.
doi:10.1073/pnas.0400981101

.. .. .. .. .. .. .. .. .. .. ..

This piece has been edited and reformatted from the original.

.. .. .. .. .. .. .. .. .. .. ..

Grrlscientist can be found on on her eponymous Guardian blog, and she's
quite active on twitter: @GrrlScientist. She sometimes lurks on social
media; facebook, G+, LinkedIn, Pinterest.
Tags: biogeochemistry, Biston betularia, carbon fixation, carbonic
anhydrase, convergent evolution, cyanobacteria, molecular evolution,
natural selection, peppered moth, Ros Rickaby, Royal Society, RuBisCO

Photographs:

Credit: P. Carrara/National Park Service/public domain A close-up of
PreCambrian stromatolites that are about one billion years old (located in
the Siyeh Rock Formation at Glacier national park in Montana).
Stromatolites are fossilised cyanobacteria biofilms. Cyanobacteria are
photosynthetic microbes that filled Earth’s atmosphere with oxygen, thereby
causing the extinction of nearly all oxygen-intolerant life forms on Earth.

Two wing colour traits of peppered moths, Biston betularia;
charcoal-coloured (melanistic; R) and pale-coloured (L) forms on a green
background.

Credit: Original work by Mike Jones (Adenosine) Overview of the Calvin
Cycle pathway. Balls represent atoms as follows: Black is carbon. White is
hydrogen. Red is oxygen. Pink is phosphorus.

--
Lawrence F. London
lfljvenaura@gmail.com
https://sites.google.com/site/avantgeared/ <http://www.avantgeared.com>
https://plus.google.com/+Avantgeared
Ello: https://ello.co/ecoponderosa <https://ello.co/ecoponderosa>
Twitter: @ecoponderosa <https://twitter.com/ecoponderosa>
Reddit: ecoponderosa
Cellphone: lfljcell@gmail.com



  • [permaculture] How chemistry affects the evolution of life (SciLog article and YouTube video), Lawrence London, 03/21/2015

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