
Plants repeatedly got rid of their ability to obtain their own nitrogen - curtis
https://arstechnica.com/science/2018/05/plants-repeatedly-got-rid-of-their-ability-to-obtain-their-own-nitrogen/
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chiefalchemist
> "Use it or lose it" applies to genes as much as (or maybe even more than)
> anything else. Genes involved in biological processes are lost if the trait
> they confer is unused or unnecessary."

Why would this be true? Can't a gene be dormant? Or perhaps over-ridden but
another gene or genes?

Or is, over the long haul (read: __many__) years any and all genes will
naturally mutate (that is, be lost). Then if the "replacement" is more
advantageous, the replacement will persist.

Fair enough. But that's not use it / lose it per se. It's still in use, but
less so (and is over time replaced).

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vertexFarm
While you make a significant distinction in that evolution does not
necessarily make a decision to eliminate unused traits, most traits that
consume resources and energy do get culled as it almost universally improves
survivability.

After all, one of the things that's so hard for us to grok about evolution is
that it's not a goal-oriented process in any way. It's not engineering, it's
the process of random chance and what can persist.

For example, a lot of people think that all our junk DNA actually does
something profound and important, and while some of it probably does have a
purpose we don't yet understand, I think it's almost certain that any process
that makes a bunch of random decisions that are mindlessly culled by
environmental forces will inevitably generate some flotsam and noise in its
code. It's kind of like training AI; it definitely won't give you the most
minimalist method of carrying out that task, but it will eventually find some
way to carry it out. Almost as a brutal, automatic tropism.

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hinkley
The “survival of the fittest” phrase is a huge disservice to generations of
students.

Traits that are _maladaptive_ are culled. Ones that have no effect are
preserved, increased or diluted depending entirely on what other genes they
appear with. Not the gene themselves.

If pale eyes were not beneficial in northern latitudes, we would _still have
blue eyes_ because the norsemen had them, and they were very successful. That
gene will stick around until something forces it out of the pool because there
is otherwise nothing to stop it.

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im3w1l
In the simplest case there is a default state (e.g. eyes have color of
whatever pigment just happen to be produced there as a sideeffect of important
genes). And then there are genes that override this default. They may disable
the normal pigment genes, they may produce additional pigment, they may break
down pigment. These genes can then exist in variants (alleles). Following the
example, they may produce pigment molecules with different colors.

In the absence of selection pressure the override genes will mutate randomly.
The end state of that process are broken genes that don't do much of anything
(loss of function), and so the color goes back to the default.

For human eyes, the default is blue eyes and there are then some genes that
overrides this by producing melanin, which turns the eyes brown.

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rdtsc
I wasn't taking too much care of the grass and fertilizing it and after a few
years I started seeing more and more clover. It turns out clover fixates
nitrogen from the air. The clover took over in some areas almost completely.
After a while I started liking how clover looked.

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dmurray
This happens on my parents' lawn too. I don't understand though, if grass
grows better than clover in nitrogen-rich soil, why doesn't the grass come
back once the clover has replenished the nitrogen?

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mikekchar
If you overseed with grass seed it will. Grass and clover makes a really nice
sward. When I had a lawn (more than 10 years ago!), I eventually realised the
beauty of this. Mix in camomile for an even lusher, softer lawn. Let it grow
long enough for the clover and camomile to flower and it's amazing. The longer
grown inhibits other weeds. It's practically maintenance free -- just run over
it with a push mower every once in a while.

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bitwize
The ability to synthesize compounds is often lost when those compounds abound
in the organism's environment because synthesis consumes energy and an
organism's energy budget is limited.

Examples from the animal kingdom include frugivorous humans lacking the
ability to synthesize vitamin C, and cats lacking the ability to synthesize
taurine.

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JumpCrisscross
> _cats lacking the ability to synthesize taurine_

Where, in the wild, do find their plentiful taurine?

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drb91
Small mammals!

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saalweachter
And birds and insects!

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SomewhatLikely
I wonder if the symbiotic bacteria provide other benefits, such as fighting
off other bacteria that would attack the plant.

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jmccarthy
Fava beans! Easy to grow, fun to watch, nice flowers, tasty, and big nitrogen
nodules.

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reificator
Plus they pair well with a nice chianti.

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aetherson
I feel like this pairing lacks a protein to really balance it out.

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exolymph
Fava beans have a fair amount of protein in 'em already!

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strait
Couldn't it be as simple as as a selection of ample seed production over ample
nitrogen availability in an environment where adequate sunlight was more often
a limiting factor than adequate nitrogen. It takes significant energy to
produce the root exudates that encourage and feed the specialized symbiotic
bacteria that will fix some amount of nitrogen for the roots. The plant
already needs lots of energy to build it's carbon structure and immune system.
Then more energy for seed production, which is the most important of all. This
energy has to come from sunlight. In growing competition with other taller
plants and trees, sunlight is often greatly diminished. The plants that
'stopped' producing these exudates and used the available energy in structural
fitness / robust seed production were able to compete more effectively as a
species over a larger area.

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rumcajz
This may be an evolutionary stable strategy
([https://en.wikipedia.org/wiki/Evolutionarily_stable_strategy](https://en.wikipedia.org/wiki/Evolutionarily_stable_strategy)).

If nitrgoen-fixating species already cover N% of the niche, other species may
not be pressed too hard to retain their own nitrogen-fixing ability.

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oever
Yay for outsourcing.

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anomaloustho
How do non-symbiotic plants normally process their nitrogen into ammonia?

Article didn’t mention.

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undersuit
Ammonia and other nitrogen containing molecules are already in soils in
varying quantities and are taken up by the roots like other nutrients.

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hinkley
This article is showing its biases. You only need to fix nitrogen in a
_monoculture_ , and rather than giving up on that idea they’re going to keep
trying to make plants that are everything to everyone.

If your ecosystem contains nitrogen fixers you can scavenge nitrogen from your
neighbors. In some cases this could be construed as a second symbiosis: A
vining legume is working with the bacteria for nitrogen and its neighbors for
loft. It has access to more sunlight in the spring, and can lay down more
nitrogen before the trees wake up. At which point the trees have access to
more nitrogen for manufacturing leaves.

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perpetualcrayon
To my way of thinking, this makes a ton of sense.

I don't think Darwin got it right. It's not "survival of the fittest". It's
"survival of that which can find its place in an ecosystem".

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5DFractalTetris
I think it's "Survival of the Fittest Ecosystem," actually. So not like,
"Humans are fittest," but instead, "Human eating corn cow sheep soy etc. while
building machines is fittest"

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eternauta3k
It's interesting how selection acts at different levels. Individuals are
reasonably good at enslaving their cells so they cooperate (when they don't,
they get cancer).

But cooperation between individuals is much less effective, not to mention
between species. An ecosystem is incapable of enforcing a contract between
species to prevent a selfish species from destroying the whole thing.

