Bizarre sea slug is half plant, half animal | Hacker News Reader

Bizarre sea slug is half plant, half animal

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106 pointsabsconditus46 comments

Any chance of genetic modification so that I too can utilize photosynthesis? I love food, but it'd be nice to not have to worry if I was stranded on a deserted island in the tropics.

You could breathe your homegrown oxygen too that way!

On a more serious note, the sun puts out about 1KW per square meter of receiver that is exactly perpendicular to the incident rays, in full sunlight. So theoretically there is enough power there, but in practice photo-synthesis is not efficient enough to make this happen, typically somewhere around 5% of the energy gets captured, and that's for a very dark plant. So if your cross section towards the sun is .2 m^2 and you convert at 5% efficiency then you can expect about 10W from that in usable energy. There is a reason leaves are relatively flat and can change orientation.

http://en.wikipedia.org/wiki/Photosynthetic_efficiency

It's not easy, being green.

Of course, you wouldn't need oxygen. You need oxygen to break down compounds; you need carbon dioxide to build them. Your lungs would have to switch to absorbing CO2 and expelling O2.

Now, on the other hand, if you continued to eat food AND synthesized, that could get pretty cool. I'm not really sure what you'd wind up expelling in that case.

You still need oxygen. Plants breath in oxygen too. Photosynthesis does not magically create "bio energy". Or rather, photosynthesis does not directly regenerate ATP. It creates glucose which then has to be broken down for ATP via Krebs cycle (same thing you do).

I guess in theory, you COULD do everything anaerobically. But then your efficiency drops even more.

A plant still produces a net positive of oxygen though, correct?

Only during the day from what I've read. At night they consume a net amount of oxygen.

The amount consumed is smaller than the amount produced, so there is a net production over the whole cycle.

Sort of, a plant converts a net positive of CO_2 to O_2.

This is also another one of those cases where some folks can misunderstand the statement to believe that plants somehow take in all this CO_2 and scrub it of Carbon. Not really, that Carbon becomes the plant itself. The amount of C's that a plant pulls out of the CO_2's is nearly equivalent to the plant's dead weight. This is important to understand, because old growth forests don't actually remove net CO_2 from the atmosphere, they just fail to release it. If you cut down the forest, the dead plant matter starts decomposing and/or burning and then CO_2 and/or methane goes back into the atmosphere.

Or at least, that's how I understand it.

Essentially correct. There may be some second order effects that help established forests pick up some more carbon out of the atmosphere, especially if the atmosphere gets more carbon laden than it used to be when the forest was formed. The Economist had a special report on forests last week that had some details on the climate benefits of old forests.

Also, when you're the only guy on the block that's able to turn energy into a useful form, you tend to get eaten a lot.

This brings up a somewhat more scary discussion: It's more efficient to be a cybernetic organism than a gene-modified human with genes from plants.

If I get this correct, this (cited) Wikipedia-article says that solar cells with a 0.01 m^2 surface area would produce approximately 1.4 watt. Multiplying 1.4 watt by 20, to get a 0.2 m^2 surface area, gives us 28 watts.

http://en.wikipedia.org/wiki/Solar_cells#Energy_conversion_e...

For reference, a 2000 Calorie per day diet translates to about 100 Watts.

2K Calories of energy per day translates in to 1163*2 = 2326 Watt-hours, which you could interpret as an average consumption of 96.91 Watts over the course of a day.

It would be a lot easier if you hadn't been conceived, yet.

But you'd get fat by being outside. That seems suboptimal.

Weight control: wear a jacket.

Alternatively: body paint.

Not if you're a programmer.

I'm guessing you'd need some huge surface area to power a human with photosynthesis.

Perhaps an acre (wild guess)? Maybe someone could look that up?

http://duckduckgo.com/?q=calories+in++1+pound+of+whole+wheat...

Gives 1538 Calories per pound of whole wheat flour.

According to these folks an acre of wheat yields 42 bushels: http://www.wheatfoods.org/AboutWheat-wheat-facts/Index.htm

At 60 pounds/bushel that gives you 2520 lbs. * 1538 Calories = 3875760 Calories / acre / year. We'll divide by two to assume you're mixing wheat with some foods that are a little less calorically dense, because you'll want at least some green leafy veggies and beans for iron and protein, and that gives us 1937880 Calories per acre per year, divided by 365 days in a year yields 5309 Calories per acre per day.

So, back to the original point, it looks like you can easily power a human using half an acre of land and photosynthesis. Possibly one quarter of an acre if you're willing to live on bread alone. (Whole grain being not so unhealthy as white.)

I doubt wheat is the most energy efficient plant. I'd guess it's actually pretty poor, although it may be one of the best in terms of us eating it.

That said, you tend to lose a ton of efficiency if you grow a plant, cut it down, process it, and then eat it. That plant is doing a lot of things other than making you food. If you are producing your energy straight from the sun, you'd do this a lot better. I'd say you could get away with far less than your estimate.

But man does not live by bread alone!

2000kCal = 2.3kWh Assuming 5% conversion efficiency (http://en.wikipedia.org/wiki/Photosynthetic_efficiency) Win = 46.5kWh. "standard" solar radiation equals approximately 1kW/m^2, so given 12 hours of solar exposure per day this works out to about 3.9 square meters.

Whenever I do these kinds of calculations I'm always amazed at how much power the sun is able to provide on a square meter 93E6 miles away!

So you'd be okay with a moldy green look?

Hmm. Women who want to stay slim + algae. Maybe we can finally get real live Orion slave girls… (Not actual slaves. Not actually from Orion. No refund possible. Ask your dermatologist, divorce lawyer and Michael Okuda for side effects)

green women sounds kind of sexy

I want to be powered by photovoltaics!

Sure! Coax a retrovirus into reverse-transcribing some chloroplast-supporting genes into your skin cells, eat a salad, and you're all set!

And we already have retro-virus genes in our genome.

"Half plant, half animal" seems incorrect: it's an animal that has borrowed some DNA and cell parts from algae.

Or vice versa: It's plant DNA that has infected an animal and uses it for reproduction. The algae's chloroplasts haven't figured out how to survive the step into the next generation, yet, though.

Right. If the genes were giving the snail sores, we'd call it a virus. Perception is reality

What I would call reality is the percentage of the genome from the original snails and from the algae.

That's probably a good way to look at the issue.

Outcome is reality.

I recall a definition of mental illness that requires it to have a negative impact on the person.

A mutation may be adaptive or maladaptive. It depends on the creature as a whole - and also the current environment.

That environment is analogous to the market part of "product+market" for a startup: the identical technology/product can be a winner or a loser, depending on extra-product factors.

Yes, outcome is reality. But the words we use, plant taking over snail or snail stealing plant genes, are shaped by perception.

I see that your reply to davidw was about actor/object; but I was replying to crayz, who was talking about "borrowing some DNA"/"being infected" ie. whether the effect was good or bad. hmmm... at least that's how I read him, anyway; but maybe he was also focusing on actor/object... regardless, I still say I have a valid point! :-) Good day, sir!

But the plant DNA is encoded into its genome. "Half" is stretching it, but it's certainly partly plant since it received the plant genes via horizontal gene transfer from the algae.

Mitochondria are hypothesised to have originated from separate organisms. Could this be additional evidence of the same process half way complete?

http://en.wikipedia.org/wiki/Endosymbiotic_theory

Here's a clip of it moving.

http://www.youtube.com/watch?v=yQNIpW0LlsU

Follow the blog spam.

So this article is a summary of, and links to http://www.livescience.com/animals/green-slug-animal-plant-1...

But that article only mentions its source "The finding was first reported by Science News" w/o a link. Some googling turns up:

http://www.wired.com/wiredscience/2010/01/green-sea-slug/

which appears to be the original reporting.

The article is actually from Science News. This is evident by the byline and the Science News logo near the top of the article. I apologize for not doing better checking.

http://www.sciencenews.org/view/generic/id/53496/title/Sea_s...

Notice the publication date on that is Feb 13th though. Science News articles sometimes appear first at wired.com for whatever reason.

And posted here: http://news.ycombinator.com/item?id=1051809

I seem to remember a while back when scientists discovered a jellyfish with similar attributes. Does anyone else recall?

Good example for an argument with anyone who doesn't believe in evolution.

What new capability now exists that didn't before? Not for the snail, but over all.

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