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Is Hydrogen gas present in biogas, and does it spontaneously ignite?
Is Hydrogen gas present in biogas? As it is highly inflammable, may it ignite the other gases like methane?

What's your question here? Are you asking why biogas with hydrogen doesn't spontaneously ignite?

first question is whether Biogas constitutes Hydrogen and if yes why doesn't then the biogas spontaneously ignite?

cf. http://biology.stackexchange.com/questions/7336/gas-from-bacteria-thats-not-methane

The constitution of the biogas depends greatly on its source and the fermenting microbe. But in general, it does contain hydrogen about 0-1%. Even if it did contain large amounts, the mixture would be inflammable, but it would not burst into flames without any external igniter, which could be any small fluctuation of heat if the mixture is too unstable. But in general, an inflammable gas doesn't start burning on its own.

The auto ignition temperature of a combustible mixture of hydrogen in air is 500 degrees C source - Wikipedia. It will not spontaneously ignite, some part of it must first reach that temperature through a spark, flame, or other heat source.  Once it ignites, the methane of course will burn too.


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Data Bias in protein-protein interactions data
Databases like STRING have so many predicted as well as experimental interactions data for many organisms.However there is a bias in the data which they have?.

a)The first is gene co-occurrence  which is more like a circular argument.
b)And the second one is that all interactions that are predicted computationally are tested for experimental interactions.This leads to a bias in the interaction data available for organisms in STRING.

How do we overcome this data bias while using STRING interaction data for analysis purpose?

a)Avoiding evidence channels of gene co-occurrence is one way.Is there any other way other than this?
b)How to statistically say that the bias is not governing the data or any way to test statistical significance of the data bias?

I'm one of the STRING maintainers, so I hope I can clear things up a bit.
Gene co-occurrence: genomic context methods are very useful for bacterial genomes, but not so much for eukaryotes. However, they are actually the most unbiased data we have, since there's no human influence (beyond selecting species for sequencing).
Benchmarking: Interactions predicted from text-mining etc. are benchmarked against the KEGG database. However, this doesn't necessarily lead to biases, as this benchmarking is basically a calibration step.
Actual biases: For eukaryotes, most interaction data comes from the experimental, database and text-mining channel. All of these are biased in various ways: e.g. there are study biases (disease genes will get more attention) and technical biases (some proteins are hard to work with)
As we don't know the actual set of protein-protein interactions, we can probably not test for biases in the data.

Could you please answer this question http://biology.stackexchange.com/questions/25914/string-id-allelic-differences-and-splice-variants

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STRING ID - allelic differences and splice variants
STRING has protein (amino acid sequences) mapped to a single gene ID.
I have these doubts with respect to STRING ID.
I find that

1.All alleles of a single gene share the same STRING ID and
2.Especially in Eukaryotes, splice variants of the single gene(which might translate to different proteins) share the same STRING ID.

Does STRING take into account these two things like UniProt and have different IDs based on allelic differences and splice variants?If so,how?

At this moment the STRING database is not accessible. Can you give an example?

Rvxxxx is a gene id.

STRING uses only gene ID to map protein sequences

STRING is now working.Another example STRING ID:4932.Q0010 (Saccharomyces cerevisiae) AA sequence:MYYIMFLYNMLLIIILIFYSIVGVPIIIFNNNYYWDPDIFLFIIYYFIKFIIIFNLYLYYMINYIVYTPSGSPPGRGTYI LLYNMLYSYNMFIDYVMKFITCVTYMYLMFWLLSPTPSPYYVSEVPVS

please don't use (non-biological) acronyms such as w.r.t - it makes things unnecessarily hard to read (http://meta.biology.stackexchange.com/questions/104/use-of-abbreviations-and-acronyms-in-answers)

okay changed it.

STRING does not distinguish between different products of the same gene. E.g. for human, the protein identifier you see (ENSP...) corresponds to the longest splice form for each gene (ENSG...). Therefore, STRING won't help you if you need to distinguish between splice forms.
Splice forms are merged because for most sources of evidence, there is little data for the interactions of individual splice forms.

What about allelic differences?

we also don't distinguish alleles at all, we don't even retrieve them from Ensembl

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Why does ostrich meat look and taste more like beef than chicken?
Some time ago I tasted ostrich meat, and what was amazing to me was that the meat very much resembled beef, much more than it resembled chicken, turkey or duck meat. And even more than lamb and pork resemble beef.
The resemblance is both in look, both raw and grilled, and in taste (only tried grilled). I would have thought that the meat of related animals would have similar taste. Why is it that the meat of an ostrich, which is a bird, doesn't taste like that of other birds?
Warning, the following links are to pictures of meats!

A picture of beef
A picture of ostrich meat
A picture of chicken meat

There is a very plausible explanation here.
Basically, it explains that meat colour is due to the protein myoglobin (a haem-containing protein related to haemoglobin). There are two types of skeletal muscle: fast-twitch and slow-twitch (Wikipedia). Slow-twitch muscle is red muscle because it contains lots of myoglobin. Fast-twitch muscle is white muscle, containing less myoglobin. The Wikipedia link explains a little more about these muscle types and their functional differences. Evidently the lifestyle of the ostrich dictates that it have more fast-twitch muscle, and so it has red meat. It isn't unique in this: duck and goose are classified as red meat too.
Incidentally the role of myoglobin is to improve the rate of diffusion of oxygen from the haemoglobin in the capillaries through the cytoplasm of the myocytes to the mitochondria. It has also been suggested that it acts as an oxygen storage mechanism in diving mammals which have very high levels of myoglobin in their muscles, but this storage function is unlikely to be important in other mammals, despite what you may read in textbooks.

Great answer, and it also explains why tuna has red-meat-like qualities.

"Slow-twitch muscle is red muscle because it contains lots of myoglobin"
"Evidently the lifestyle of the ostrich dictates that it have more fast-twitch muscle, and so it has red meat"
Huh?


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The evolution of dogs through domestication and artificial selection
I am currently reading Richard Dawkins's book 'The Greatest Show On Earth: The proof for evolution' and in the second chapter he talks very much about the evolution of dogs.
He says centuries ago there was only such dog-like creature as the wolf, but in a matter centuries the wolf has evolved into the many breeds of dog we have through artificial selection conducted by man.
This to me seemed very peculiar and quite frankly untrue, and I may be getting the wrong end of the stick and he is in fact being analogous, although I'm pretty sure he's not.
So, did wolves evolve into the many breeds of dog we have through artificial selection conducted by man?
If so, how many centuries did this take?
(Dawkins's point was that if the wolf can evolve into the vast amount of breeds of dog we have at the moment from artificial selection over a matter of centuries, then surely over many millions of years, the evolution we claim to know of through natural selection could definitely have happened).

What makes you think it is untrue? Domestication is the process of artificially selecting a wild species in order to benefit humans.

@nico The reason it would seem quite untrue is because (to me) even through artificial selection, evolving from a wolf to the vast amount of breeds of dog we have now in centuries seems like a very short amount of time. But I do accept it's true and don't doubt him. Do you know roughly how long ago it was when only wolves were present?

Would you say my reason seems unreasonable?

@Olly Your reasons are in fact spot-on but if I remember correctly (but it might have been another of his books), Dakwins explicitly mentions that in order for changes to occur so fast, the variability in the genome has to be already present.

That would make perfect sense, I couldn't imagine it happening in such short time if there wasn't variability in the genome, thank you.

I just wanted to add that although we are pretty confident that domestication of wolves created domestic dogs in pretty short order.  In addition to the fact that they can still interbreed and the taxonomical resemblence of dogs to wolves and finally the genome sequence, probably the most awesome evidence is the domestication of the silver fox.
Russian biologists at the Institute of Cytology and Genetics (ICG) in Novosibirsk, Russia in 1959 started with 130 foxes.  Even though they can be bred in captivity and they are close to dogs, they had never been domesticated.  By selecting the animals with the least aversion to human contact over 10 generations, they were able to breed foxes that were very much like domestic dogs.  They follow humans around, enjoy contact with humans, and generally act friendly.  In addition they also bred the most averse animals to human each generation as a control (sure enough these animals would rather nip your fingers off before letting you rub their belly!) there are videos of these animals floating around.
Ten generations of animals ended up being less than 20 years.

Yeah I read about this, their appearance even changed dramatically!

@OllyPrice like dogs, their appearance change is an unexpected effect of such strong selective pressure.  The fact that the coat changes color, the ears get softer and floppier.  Its strange how they sort of get cuter when they are domesticated.  This should be a coincidence, aggression and physical competition might be associated traits, but its a little odd when you think about it.

+1 for the fox example! This shows how few genetic polymorphisms and how fast domestication (ie, taming) can occur. Other studies have shown that a few genetic polymorphisms can lengthen snout, shorten legs, alter other characteristics which are used to distinguish a breed of dog.

You say strange, but then surely (and this is where natural selection would no doubt come in), the genes of those dogs that were 'cuter' AND friendlier would have passed on more often than the others.

In the case of dogs, yes.  In the case of the foxes the scientists were trying to be pretty clinical about it. They had a test where someone would approach the animal and they would try to rate the reaction alone.  ugly but friendly foxes were a distinct possibility here.  The fact we think they may be cute might come from some other interesting possibilities, including that friendlier genes may come from some arrested development in the animals which may maintain juvenile traits for instance, which are usually cuter. just a thought.

According to Serpell, 1995 (http://books.google.co.uk/books?id=I8HU_3ycrrEC, page 8), wolf bones in association with human bones have been found from as early as the middle pleistocene (126,000–781,000 years ago). I think we're talking about more than a few centuries here :) It's still relatively little in comparison to naturally selected evolution, but that's probably the point he is trying to emphasize.

If I remember correctly his argument was that the transformation (if I may use such a word) from wolf to dog did indeed occur over a much shorter time span. I’m pretty sure Dawkins was making a factual claim, and since he’s well-versed in dog-breeding and researches all his books with great care, I’d be surprised at such a blunder.

Later on in the book he does mention that it's 1million years ago that the wolves started becoming village-scavengers (which of course kicked off the domestication of them), I had asked this question before I read that part.

Many dog breeds went through genetic bottlenecks about 200 years ago. Many of today's breeds either did not exist a couple to few hundred years ago or looked rather different than the breed looks today. It doesn't take long to change the characteristics when selective breeding occurs.
One may need to consider the co-evolution of Homo sapiens and Canis familiaris. Our close friendship with dogs tipped the balance in favour of modern man over the Neanderthals, who had previously occupied present-day Europe for a staggering 250,000 years. More on how dogs helped human hunt and be watchful is explained here.
This other report, just out, states that modern dog breeds are genetically disconnected from ancient ancestors. Cross-breeding of dogs over thousands of years has made it extremely difficult to trace the ancient genetic roots of today's pets, according to a new study.

Pat Shipman's suggestion seems very unlikely, earliest evidence for a domestication event of the gray wolf is maybe 32,000 or 40,000 years ago, the last Neanderthals died out 42,000 years ago in Gibraltar & 44,000 years ago in the rest of Europe, the math doesn't stack for dogs to have any involvement in the Neanderthals demise.

Hmm.. on the other hand (sorry, I think I was sitting on it earlier) the common ancestor of wolves & dogs obviously predates those domestication event dates (which come from genetic evidence rather than fossil record iirc), obviously those animals may have been extant as partners used by humans for some time b4 the (probably not so deliberate) selective breeding diverged them from the wild ones that evolved into wolves, that may push the association with humans back far enough it is possible.

A couple more links to compliment your one: National Geographic / The Guardian

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Is there a standard definition for plant "maturity"?
Is there a species-agnostic metric for identifying plant maturity?
There seems to be plenty of literature defining life-history stages for specific crops, but it is not clear if there is a generic definition.
In the context of crops, I would like to be able to identify the stage at which plants are no longer exhibiting juvenile traits.

Exactly what types of traits are you looking for? First onset of flowering seems to me to be an obvious choice, since sexual maturity is the definition of being an adult. Do you find this insufficient, and if so, why? It is generally easier to use "positive" definitions (presence of traits) than "negative" ones (e.g. lack of juvenile traits).

Also, I realize that some plants only reproduce clonally, but this should be less of a problem(?) in crop plants.


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What controls leaf senescence in deciduous tree species, and how can I predict it?
If I want to predict litterfall, what data do I need to collect, and what statistical model might I use?
For example, I might use the following coding to record phenological stage every other day, or perhaps once per week:
|value| description
|-----|--------------
| 0   | all leaves fallen
| 0.5 | most leaves fallen
| 1   | no more green in canopy half of leaves have fallen
| 2   | most leaves yellow or red few leaves have fallen
| 3   | noticeable reddening or yellowing, green still present
| 4   | summer condition

Once I have these data, I can also collect weather data. Now, say I want to predict the day on which each of the transitions ($4\rightarrow 3$, $3\rightarrow 2$, etc) occur.
Many studies use a temperature metric of growing degree days $GDD = (T_{max}+T_{min})/2-T_{base}$, but I have also seen chiling days and photoperiod used to predict changes in phenological stage. I would like to develop a function (statistical model) $f$ that would allow me to predict a date of state change from environemental variables, such as $$D_{4\rightarrow 3} = f(GDD)$$
My questions:

what controls litterfall? Is it photoperiod, temperature, other?
do the controls vary by species?
is there a "standard" approach to modelling senescence?

there was a related question on stats.SE (about modeling bud burst) http://stats.stackexchange.com/q/9797/1381

You might check out the R package chillR by Eike Luedeling, and his various papers documenting its use .

One can sometimes notice street lights delaying the annual shedding of leaves in some species (a well-lit branch will be mostly green while the rest of the tree is turning). So at least part of it would be day/night length in at least some species.
I would expect, however, that the answer varies based on species, genus, and/or family, and that there are probably multiple causes at work (one obvious alternate cause being temperature). Just going from memory of my personal observations, years when autumn weather patterns start earlier do tend to have trees turn and lose leaves earlier, so it's not all day/night length.
Drought is also a factor. I live in a seasonal-rainfall part of the world (US Pacific Northwest), and if summer is drier than normal (and normal is pretty dry), by mid-August many of the native deciduous trees will be starting to drop leaves. (Not all of them, but some of them, definitely more than just a few, will be turning and dropping.)

Can you provide some details with references (at least for some species). It looks more like a long comment as it is now.


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Why is mammal coloration so dull?
I have seen species of birds, insects and fishes with splendid colours. But when it comes to mammals (including us humans), they almost always appear in shades of brown, grey, orange, or in black and white. I don't recall seeing any pink, green and purple. Why is that so?

That mandrill face in the picture you uploaded is pretty brightly colored.

Great question. At least according to this BioScience article, it seems like most of the answers are still unknown. No time to fully review it now, but this paper in PTRSB by the same author looks very good, and basically takes as its starting point that black and white stripes / spots is as colorful as mammals get, and is already surprising in mammals, "a class of vertebrate generally thought to be drab and cryptic".

Most mammals have poor colour perception, which might be the reason for the lack of bright colours. Plenty of mammal species are very contrasty with deep blacks and bright whites on the same animal, which might be all that's required. Primates have much better colour perception than most mammals, and there are a few monkey species that have bright blues and oranges. Of course, I have no idea whether mammals were more colourful before colour vision was lost; this is pure speculation on my part.

I don't think, there is a precise answer about the evolutionary mechanisms, but "mechanically":

mammals have principally just two types of pigments: eumelanin and pheomelanin, both of which have their color variants, but within a known range. Bird pigments, besides melanins, include carotenoids and porphyrins. Arthropods generally have carotenoids, melanins and ommochromes [and other pigments?]. E.g. carotenoids and ommochromes alone can create rather "exotic" coloration from a mammal point of view (green, pink, violet).
both birds and insects actively utilize iridescence. With fur it seems to be technically much more difficult to achieve than with feather or scales.
many (most?) mammals do not differentiate colors. Birds have much better vision abilities in this respect. From a selectionist point of view this cuts out a considerable part of selection acting upon coloration, which could otherwise produce broader spectrum of phenotypes.

Nice answer. Come to think of it, no wonder our eyes are most colorful because it is made of carotenoids. Thanks!

In addition to the arguments presented in the accepted answer, I would like to add that most species of mammals are red/green colour-blind. This has to do with the fact that for much of their evolutionary history, mammals were nocturnal creatures and so the ability to see different colours wasn't necessary.
This dates back to the mesozoic period when mammals had nocturnal lifestyles in order to avoid predation from dinosaurs.
Here's an article that summarizes recent research on this topic: http://www.utexas.edu/news/2012/10/29/effects-prehistoric-nocturnal-life-mammalian-vision/

The Answer is simple..EVOLUTION..
The colour of an living organisms depends on 2 things 1) attracting other sex. 2) escape from the predators.
In birds and insects: They doesn't much depend on other sex for living(except for the process of reproduction)and there is no need t exhibit  physical work for attracting other sex... For example if you take a peacock the male needs to be colourful to attract female. but there is no physical work....Let The Other example be some Insect,then if it is colourful.. a predator may not eat for its bright colour..
this made insects and birds evolute into colourful..
But in mammals. the attracting and escape both depend on physical work... a lion being handsome cannot attract lioness..  :P It need to be physically healthy to escape from predators and give an enough competition to other lions in his territory...
this made evolution for mammals much depend on their capability of body.. rather than physical attractiveness.. for example in a forest a tigress will obviously pair with a Tiger which has more territory than a more attractive handsome tiger without territory(this is not a case with insects)..

This isn't really a good argument. Mate choice in mammals (as in other creatures) is complex. For example, I'm pretty sure the character of the mane (size?, colour?, fluffiness?) plays a role in mate choice, since it's the most obvious reason for the strong sexual dimorphism.

I think that the basic concepts here are right on – there's a balance between attracting the opposite sex and hiding from predators (crypsis); among other strategies, including putting off predators with bright coloration (aposematism). However, the answer is a bit unclear and it would be very nice to see some references.

sorry for the ambiguity.. i have just edited my answer adding some more examples.. I have a video on y insects and birds have more colourful than mammals.. Its a documentary by discovery "PlanetEarth"..

Unfortunately, your edits don't address the main problem. Your entire premise that mate choice in mammals doesn't depend on "physical attractiveness" isn't supported by evidence. Lionesses choose their mate partly by the attractiveness of the mane, several primates have rather conspicuous sexual displays (the inflated cheek pouches of orangutans, the silver fur on the back of the silverback gorilla, the bright facial patterns on mandrills, etc.).


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Why did life not evolve to use radio?
We use electromagnetic communication everywhere these days. Cell phones, wifi, old-school radio transmissions, television, deep space communication, etc.
I'm curious about some of the possible reasons we have never seen biological systems having evolved to use electromagnetic, i.e. radio, for communication. The one obvious exception to this are organisms that generate their own light, i.e. bioluminescence. Cuttlefish are masters of this, and many other species as well.
It seems like bio-radio could have offered all kinds of evolutionary advantages for animals capable of using it.
Are their basic physical limits in chemistry, or excess energy requirements or something that would basically have made this impossible? Or was this perhaps just something that life never evolved to use, but would otherwise be possible in evolution?

Also, don't forget magnetotactic bacteria

Light is an electromagnetic wave. The only difference is wave length and energy.

What about Sharks?

Life did evolve to use radio, we use it all the time.

See electrocommunication, weakly electric fish and Mormyridae. They use 500 Hz electric sine signals (however, AFAIK using conductance of water, not - electromagnetic waves).

All life generate and absorb EMR, outside of the light spectrum. The fact that there are only a few species known to actively sense or use frequencies above or below the infrared-ultraviolet spectrum, may in part, be due to our inability to recognize those structures.  I would add my own answer here, but perhaps I don't have the reps for it?

Does this answer your question? Why do some bad traits evolve, and good ones don't?

There is a very different mechanism for generation (and detection) of ultraviolet, visible and infrared light vs radio waves.
For the first, it is possible to generate it using chemical reactions (that is, chemiluminescence, bioluminescence) with a typical energy of order of 2 eV (electronovolts). Also, it is easy to detect with similar means - coupling to a bond (e.g. using opsins).
For much longer electromagnetic waves, and much lower energies per photon, such mechanism does not work. There are two reasons:

typical energy levels for molecules (but it can be worked around),
thermal noise has energies (0.025 eV) which are higher than radio wave photon energies (<0.001 eV) (it rules out both controlled creation and detection using molecules).

In other words - radiation which is less energetic than thermal radiation (far infrared) is not suitable for communication using molecular mechanisms, as thermal noise jams transmission (making the sender firing at random and making the receiver being blind by noise way stronger than the signal).
However, one can both transmit, and detect it, using wires. In principle it is possible; however, without good conductors (like metals, not - salt solutions) it is not an easy task (not impossible though).

Why is the thermal noise not a problem in mechanical devices then? Is the only reason the better conductivity of the material?

Thermal noise is devastating for molecular devices, as detectors/emitters (two-level systems) are all the time saturated (so e.g. a photon has the same probability of being absorber and to steal excitation). For macroscopic currents there is no such mechanism and one can easily go beyond the thermal noise (so for animals its only a technical problem of getting good enough conductors and generators of high frequencies). Moreover, AFAIK water absorbs most of radio waves (it's why submarines use sonars, not - radars), so radio communication would work only for land animals.

Wires (like tubules, axons) for electrical signaling seem to be very common in the cell world. Is it actually known that they don't have a radio wave antenna function too?

@LocalFluff Axons are not "wires". They propagate signal due to depolarization, not - conductance.

Okay, I'm lost in this weird universe of microbiochemo whatever. Fascinating stuff. But there are plenty of microtubules around, up to a couple of millimeters long. Life seems to like to make tubes and strings of different kinds. My wild thought is that maybe they could generate and react to radio waves? Some speculate that they might even have quantum mechanic properties. Water is bad for radio, but on the scale of a few cells maybe that doesn't matter much.

Point of fact: Technological EMR absorption, raises the average human body temperature by a significant fraction of a degree, which consequently reduces our caloric requirements. We may not yet have a full enough understanding of all the ways that each part of the EM spectrum may be used, sensed/emitted by life forms. If you stand to too close to a high enough power output radio antenna, in some RF bands, you will "feel the heat". In other cases, electrostatic charges raise the hairs on our skin.

So an interesting follow up question would be, why didn't organisms evolve to incorporate metallic conductors into their body

Because the intermediate stages are not evolutionarily favoured. That's why.
Sound and light perception are useful without any generative capability. An organism with a tiny amount of perception for either of these things has an advantage over those without; and an organism with a tiny amount more has an advantage over those with a tiny bit less. This advantage forms the basis for selection and thus improved sensory capabilities (balanced, of course, by the cost of those capabilities).
Being able to perceive radio on the other hand provides no useful information about the world at low level perception so even if an organism was to randomly mutate so as to detect radiowaves* there would be no selection for this ability, and thus no mechanism to drive the evolution of advanced radio reception. Without the ability to perceive radiowaves there is no possibility of evolving the ability to generate radio signals in a controlled manner.
*-In fact, since radiowaves generally interact very little with organic materials unlike heat, light and sound even this first step of random mutation is much less likely than for sense that have evolved.

I find the "intermediate stages" along with "no useful information about the world" argument more satisfactory than thermal noise argument.
Terrestrial animals preferred visible light to be visible because of Sunlight spectrum. https://en.wikipedia.org/wiki/File:Solar_Spectrum.png
Sound has high attenuation, so it is more fit for local communication without attracting predators from long distance.

How about bats? Their ecolocation is useful without any transmitter.

@DanDascalescu: (1) What do you mean there is no transmitter? Bats create the sound they listen for echoes of and (2) Bats' echolocation works by further evolution of the already-selected-for abilities to hear and make sounds.

@JackAidley, I meant without another transmitting animal.

@Vikas Multicellular organism have many cells which communicate with each other, using many complicated chemical and electrical signals. The first multicellular individual that somehow mutates to use radio could certainly benefit from it. All cells in it would then have the same genes, the same radio channel.

@DanDascalescu It was. many animal can produce ultrasound. Cat for example communicate in ultrasonic we human don't hear normally. Animal other than us mostly nocturnal need ability to find prey and aware of predator. They evolve to hear wider range of sound than us. Then they communicate with that range. And some evolve ability to do echolocation after that

@LocalFluff the problem is "using" radio is not one mutation it is many many mutation because there is no useful amount of ambient radio around. There already is useful amounts of, sound, visible light, and heat.

Actually, electromagnetic communication is used by certain fish, the mormyrids and the gymnotids.  Pulse modulated in the former and amplitude modulated in the latter.
However, the frequencies used are not much greater than 1Khz, which is not what we ordinarily consider to be in the radio frequency spectrum.
There is, too,  another biological species in which the use of the full RF spectrum has evolved. Its activities even extend to the use of the UV and X-ray frequencies.
That species is our own. I am not being flippant here. We must not fall into the trap of considering ourselves as apart from nature.  Contrary to our usual intuitions, technologies have evolved autonomously within the collective imagination of our species.
The broader evolutionary model which supports this contention is outlined, very informally, in "The Goldilocks Effect: What Has Serendipity Ever Done For Us?" , a free download in e-book formats from the "Unusual Perspectives" website.

Thanks for the info about mormyrids and gymnotids. I'll do some further reading on them. I am only interested in biologically-generated radio communication, which was where my question was directed. One of the key differences between technology and biology is that the former is not inherently inheritable. A flock of birds that communicate via radio will pass that ability to their young and is innate. Human speech capability is passed innately to our young. The knowledge to build technology is sociological, not biological.

You miss my point. The evolution of technology cannot be dismissed as "sociological". If examined carefully is ti an inevitable outcome of biology.  It is so very easy to fall into that anthropocentric trap.  The mechanisms of transmission are, of course, not identical for the various phases of the overall life process.

this is a good answer - adaptation could, given proper conditions, create radiosensitive organisms I'm sure.

I just found a research about possibility of organism with loop DNA (Mostly bacteria) could use there DNA as antenna to transmit and receive radio wave around 1kHz
http://www.wired.com/2011/04/bacterial-radio/
But as other said. Communication mostly evolve from sensory organ. So the radio wave has too much noise and could not give useful information about situation. They don't selectively evolve to the point that they could be used to communicate
But the bacteria has inherently possibility from start. So they may actually do some communication

That's really interesting! Thanks for the update.

A quick comparison between light and sound vs. Radio

Light: Wavelength 380 nm -740 nm
Sound: 17 mm - 17 m
Radio: 1mm - 10e5 km

From the Planck relation, the energy of a wave is inversely proportional to the wavelength. As a result light is stronger than sound which is stronger than FM radio which is stronger than AM radio. Very likely, the energy density provided by radio is far too weak to have meaningful signal processing.
However, there are some uses in the radio frequency. Bat echolocation occurs at a frequency of 14,000 to 100,000 Hz which is well within the radio frequency.

You don't need a lot of energy to communicate anything. Anyway, radio and wifi works, so it's not a good argument.

@PiotrMigdal, I agree with that counterargument. However, electronic forms of communication via Radio and wifi have the luxury of being amplified. Yes, signaling cascades exists but certainly are not optimal compared to higher frequency channels. Your answer is certainly better.

A good point with amplification. For radio you want sine-wave amplifiers, not cascade amplifiers, so here there may be a problem as well. However, the first step is to have good wires...

echolocation uses sound not light. the mechanism for detecting sound is basically the same regardless of frequency while light has to change significantly across that difference. the detection of sound can lead to the detection of high frequency sound but an eye cannot be made to detect radio without significant changes at every level.


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How does "be altruist to those who are similar to you" evolve?
There are many cases when people commit altruism. One is relationship. I am willing to die for 2 of my children or 8 nieces, say an evolutionary psychologist. Another is reciprocal altruism, which is just a selfish cooperation rather than true altruism.

In the 1930s J.B.S. Haldane had full grasp of the basic quantities and
  considerations that play a role in kin selection. He famously said
  that, "I would lay down my life for two brothers or eight cousins".[8]
  Kin altruism is the term for altruistic behaviour whose evolution is
  supposed to have been driven by kin selection.

Is it possible that humans may be altruists not for their 2 children or 8 nieces but to say, 1000 people that are similar to them.
If so, how does "Be altruist to 1000 of people similar to you" evolve?
Note: If the answer is negative, then we will have a hard time understanding voting. Why sacrifice your time. However, if the answer is positive that humans do love other humans "a little bit" then voting, or even suicide bombing make sense. Those humans sacrifice their little time to improve reproductive success of those who are similar to them.
Answer DOES NOT have to be about humans. If you can show me why strong/weak chimps tend to help each other or whether alpha males like one another, that'll do. Of course, naturally we would expect that leaders need followers and followers need leaders. But sometimes there are behavior that defy even this complementary nature.
Similarity does not have to be genetic. For example, fellow programmers and fellow engineers tend to be gang up.... Or does it have to be genetic?

Can you rephrase the question so that the example is not directly political? There's a valid question here, but in my opinion, it's packaged in a way that is not appropriate for this site.

I see. The problem is voting is always taking from one guy to another. It's not about common goals. I am picking the simplest sample. I suppose I can make that the other way around of middle class diligent people wanting to lower tax. The truly rich don't care about tax though. Google pays like 2% income tax or something.

Also this "altruism" toward someone not related but similar may explain suicide bombing, rather than just mere voting, for example. It explains why people are loyal to their religion, etc. I think I should have used samples in animals.

I changed the questions and the packaging. However I can't find a less political samples where I can put some math in it.

I think this article may be of interest Children, but Not Chimpanzees, Prefer to Collaborate - Rekers et al., Current Biology 2011

@JimThio My objection to this question stands. I understand that your questions stems from your political beliefs, but your examples make this question argumentative.

I've removed all the overt political stuff, that is not on-topic here, this site is about biology, and not a vehicle to promote your own political ideas.

If you make a statement like "I am willing to die for 2 of my children or 8 nieces, say an evolutionary psychologist." please provide a citation. To me it seems like you refer to some pop evo-psychology material instead of a authoritative source.

The above answers are good, but have unfortunately confused some of the concepts in the theory, I will do my best to explain.
What we are assessing is how does one behaviour evolve, links with cooperation and altruism are applications of this. The process of selection in evolution removes the the worst individuals from the gene pool, thus those with comparatively good genes survive to reproduce. With physical traits these mechanisms are well understood, with behaviour there are still multiple theories which have not been concluded but our understanding of them is reasonably complete.
Inclusive fitness is the combination of direct and indirect fitness, direct being your personal fitness, indirect being fitness gained from others. In general this is measured in terms of reproductive success (RS) (the number of offspring you successfully raise to reproductive maturity). Out of this understanding came Hamilton's Rule:

                               r.b > c

Where r is the relatedness, b is the benefit & c is the cost. In this scenario the cost is a reduction in RS, the benefit is a gain in RS. Benefits are multiplied by the relatedness to the offspring. In normal diploid organisms (Gets DNA from both parents) you are related by 0.5 (half from mother, half from father), but only related to your brother/sister's offspring by 0.25. Thus, if you have two children you have a direct fitness of 1, if your brother has two children you gain an indirect fitness of 0.5. Thus, you would prefer under normal circumstances to have your own children rather than raise your brothers.
Altruism is suffering a cost for someone else's benefit, @Winawer mentions the greenbeard theory, which rests on the assumption that if you can tell someone has the same genes as you then you know that you are related to them in someway and this will be on average be greater than to any other individual. Altruism is a behaviour, defined above, and not a specific action like giving up your own reproduction, thus it is a part of cooperation and not separate from it.
It is true that there are different forms of altruism however these are all just perspectives pertaining to the same theory. ALL behaviour is selfish, reciprocal altruism is just an example of this. Reciprocal altruism, is "If you scratch my back, I'll scratch yours" (You need help now, I may need help in the future), it is altruistic because you suffer a cost for another's benefit but it is selfish because it is still in the individual's interest to help. This is where prisoners dilemma comes in, this is basically asking the question "how do I pick the most optimal situation in this scenario?"
For simplicity, it is generally ill advised to study behaviours in humans because of the implicit bias we have in our judgment on ourselves. From political and religious associations that cloud judgment to the fact that we always strive to see ourselves differently. Also, there are all sorts of ethical difficulties in actually testing and manipulating theories on us. Thus we normally study animals to get around this. However your question specifically talks about people so I will try and answer this based on biological theory alone.
Based on the foundations above, why would someone behave altruistically to someone only 'similar' to you? The biggest difficulty is knowing that we understand all the costs and benefits involved, most of the time we only know some of them and its impossible that you can know all of them because you can't know what you don't know. Humans have effectively 'bootstrapped' behaviours which are 'for the good of society' building on from previously developed behaviours. However we are still fundamentally asking a question about Hamilton's Rule. Being seen as a part of society induces altruistic behaviour towards you (because you are seen as worth something), this is good for you and the costs associated with being altruistic are usually low. Thus you would never rationally die for 1000 unrelated individuals unless you had at least had all the children you were going to have and raised them to be independent. But you would vote, by voting you suffer a tiny cost, your time, for a huge benefit. Benefits might include:

Being seen as caring for others (altruism given to you)
Possible benefits to yourself (less tax, more support, better roads, clean air.. etc)
Possible benefits to others related to you
General good moral of your community, leading to a better life.

There could be thousands of other benefits that I can't, off the top of my head, think of. The cost is negligible and the benefit is intangible but probably higher than the cost. Relatedness isn't important (so long as it is greater than 0), if the cost is sufficiently low or the benefit is sufficiently high. I hope this has helped clarify your thinking and answer the question.
For further information:

Wikipedia is great for getting an overview of terms and definitions, but remain critical of what you could be reading.
A decent book on animal behaviour in general is: Alcock J. (2009) Animal Behaviour: An evolutionary approach. 9Th edition. Sinaur Associates.
Academic papers; if you have access to them (i.e. are an academic)

Provides the foundations
Hamilton W.D. (1963) Evolution of altruistic behaviour. The American Naturalist 97 354
Hamilton W.D. (1964) The Genetical Evolution of Social Behaviour I . Journal of Theoretical Biology 7 1
Hamilton W.D. (1964)  The Genetical Evolution of Social Behaviour II. Journal of Theoretical Biology 7 17
The current controversy mentioned in another answer is from this paper, it is widely dislike but does have some support. It is slightly off topic from from the question here, but eusociality is fundamental to our understanding of evolutionary behaviour:
Nowak M.A., Tarnita C.E. & Wilson E.O. (2010) The Evolution of Eusociality. Nature 466 1057

Very good answer. Let me read. By the way, humans related fitness with brothers and sister should be .5 not .25. It's .25 from Mom and .25 from dad.

+1 for picking that all actions are actually selfish. The thing is the genes are selfish. So how come gene "be nice to fellow programmers" evolve?

Somehow I feel that even suicide bombing (the terrorist die but others can reproduce better when free sex is illegal) is still selfish. Here the cost is actually significant. Moreover, the similarity is religion, instead of genes. I guess I didn't take into account that terrorists do get paid well (by their community standard). But some variables are still missing.

For small costs altruism it make sense. I tend to observe that people treat those who have the same religion with them as "family".

This is an important question in evolutionary biology, but you need to distinguish the biological terms 'altruism' vs 'cooperation'.
Altruism in biology means giving up your chance to reproduce so that someone else can more readily.  This is not like a gorilla troop, where only one male breeds, and the rest contribute to mutual security.  A more typical example is a honeybee or an ant, where the vast majority of the hive have no ability to reproduce at all.  This happens in animals, but is relatively rare. Its causes are currently the subject of intense debate but as far as I know, the only cases are where you do this for others who are genetically similar to you.   That logic sort of plays out as you say: "My brother has kids, why do I need to have any? I'll just help out a little bit there."
Cooperation includes forming groups for mutual safety and increased competition for food resources are why you might vote or schlep down to the DMV to get a drivers license when simply getting in your car without might be just as good most of the time.
Cooperation is incredibly common in biology.  It even happens between species.  A dolphin helps a ship navigate submerged rocks, symbiotic bacteria in our gut help us digest food, but also get enough to live and reproduce.  The benefit is always win-win in such situations.
To understand how cooperation occurs spontaneously, one of the best experiments to look at is the Prisoners Dilemma experiment.  If individuals are in a situation where you are likely to see each other again later (like a society).  The most successful ones are the ones who treat each other reasonably well, even if you do look out for less reliable types.  Why do people from Northern climates have strong hospitality traditions?  "Today you (are in trouble) tomorrow me."  As the saying goes.
There are individuals who are not cooperative, but the selection forces are positive enough that those folks will regularly disappear from the group, while more cooperative types will become more numerous.
This is a significant selective pressure that you can train robots with very simple reward mechanisms to cooperate.  http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.144.2881

+1 for mentioning prisoner dilemma, which is the real issue. In cooperation, every single individuals are better of cooperating. In voting they are better of not voting. Voting are secret anyway. Ah perhaps going to voting booth is a way to hang out with neighbors. Also the cost for voting democrat is the same with the cost for voting republican? Or perhaps humans are not entirely selfish but care about others, say by 1%? But how does care about others' reproductive success, by 1% reproduce?

thanks - ive had to go over this quite a few times in the past year - glad the question came up.

The question's a little broad, but I'll answer the question in the title:  how does "be altruist[ic] to those who are similar to you" evolve.  It turns out one way is discussed by a simple theoretical model called the "green-beard" model.  In essence, it says that a gene for altruism can spread if it produces a characteristic that can be perceived by and recognized in others (the 'green beard') and promotes altruistic behaviour towards other greenbeards.
Wikipedia has a round-up of some examples of this in action;  my general feeling from reading on this is that though it's a good idea in theory, greenbeards won't be too common in practice because of the difficulties involved in keeping out mimicry (as in many signaling systems) and because of the complexity involved in creating and maintaining all three parts of the greenbeard effect on the part of one gene.  For that reason, it's been suggested that it may be more common in smaller organisms like bacteria, where this machinery can all occur in the same cell.

This answer makes sense. It still doesn't explain why humans vote.

That question answers itself if you think about what voting really is. It's the most concise way of stating your opinion - exactly what is needed if a lot of opinions are to be assessed in a short time. It's merely a device, an idea somebody once came up with and which has since proven useful again and again. I wouldn't attach any evolutionary idea to voting (except if we're talking about memes).


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Why Didn't Evolution Cause the Human Body to become Streamlined?
If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?

No single advantage drives the evolution of body type.  The advantage of streamlining is much greater for aquatic animals as water has a much greateer influence on viability. On land other concerns, defense, physical strength and size are at least as important.  Most land animals don't even move quickly.

This question seems to be based on a fundamentally flawed premise, I don't think it is really answerable due to that.

I don't think the premise is flawed, as evidenced by @shigeta's comment. I vote to reopen.

I agree - @shigeta's comment does essentially answer the question. The reason we're not as streamlined as fish is that we don't need to be!

" 'cause we're lovers, not fighters!"

If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?

As with everything in Evolutionary Biology, you must ask yourself: Gain vs. Cost?
In your specific case, the Gain is very little.  Air isn't nearly as dense as water, so a streamlined form won't show a major benefit unless the organism is traveling very, very quickly. This is why you see it in birds; raptors can travel over 100mph while diving, and at those speeds small changes in drag can mean the difference between dinner and starving. Smaller birds often make very quick turnabouts and changes in direction mid-flight where, again, small changes in efficiency can mean the difference between life and death. The cost was is worth it.
For apes and monkeys, moving very quickly isn't a case of living or dying. That's what we evolved opposable thumbs and prehensile feet(/tails) for. You don't need to run fast when you can climb a tree and simply get away from any predators on the ground. After we came down from the trees permanently, our larger brains allowed us to use tools to fend off predators - which, again, is much simpler than evolving an aerodynamic form that won't make a difference until you're running at the speed of a car.
So, in lieu of becoming a land-shark, we have hands that can use keyboards and minds that can invent the keyboard. Unfortunately, while the gains are many, the costs do include both a very long period of time where humans are helpless without parents, and an absolutely terrible form of locomotion with our upright stance on forward-pointing knees. Though you won't catch Cheetahs digging sewers anytime soon.

Who says we are not streamlined?
One could easily imagine body structures that would cause much greater drag in air and humans do not have them.


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Estimation of number of species at an earlier time
The estimated number of species on Earth, as reported in this article is around 8.7 million. I am fascinated by how nature produces such a wide variety of species.
As per my understanding, many species have gone extinct, that is, were not able to adapt to changing conditions on Earth. Perhaps the number of species before few thousands of years were larger than today. Can we estimate the approximate number of species at a given point in the past, using available data?

Nice question.  It would be interesting to try and plot the extinction of species vs speciation of a new one.  I strongly doubt it's liner over time, even if you account for catastrophic extinction events.


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Is it possible to have life in vacuum?
I just got struck by curiosity now: Intuition says no, but I've never had confirmation of it.

Define life. You can probably get viral spores that can survive and even some extremophile bacteria but in a dormant state. Would you consider something that is not interacting with its environment in any way at the moment alive?

See very similar question and answers here: http://biology.stackexchange.com/questions/2700/can-the-body-of-any-organism-on-earth-live-without-impairment-both-in-vacuum-an/2703#2703

nobody has had confirmation of this - with the possible exception of the tardigrade in space experiment and those like it in the ISS/space shuttle.

You could build robots that feed on debris, like man made satellites, that satisfy common definitions of life (e.g. Reproduce, have a metabolism etc). In general life as we know it does not do well in space because it is very cold, and not much chemically is going on to support metabolic processes. The lack of food, water and the vacuum make it rough as well.

As @terdon comments, dormant organisms can survive in vacuum. This includes lichens, bacteria, and even an animal: the ever-amazing and adorable tardigrade (Jönnson et al 2008). In 2006, tardigrades survived exposure to the vacuum of outer space with no appreciable difference in mortality compared to controls.

Tardigrade Hypsibius dujardini, a different genus than the ones sent into space, but probably equally hardy. Photo by Bob Goldstein & Vicky Madden (CC by-nc-ca via Goldstein lab - tardigrades on flickr).

Jönsson, K. I. et al (2008). Tardigrades survive exposure to space in low Earth orbit. Current Biology 18(17):R729–R731

Be able to survive it is quite different from living permanently in it...

I agree! Which is why I upvoted your answer.

No, it is not. Or at least not in the form we know life. The reason is that water (which is essential for life) boils at low pressures at room temperature. This makes life impossible in the form we live it on earth.

No, because some kind of fluid (liquid or gas) is necessary to supply resources and carry away wastes. Bacterial spores, tardigrades, etc. are in a dormant state when in a vacuum.


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What elements are a possible basis for life?
I've been told that life on earth is carbon-based, Then I got curious about one thing: What are the possible bases for life and under which circumstances could lifr based on other elements exist?
If the existence of a silicon-based life is possible and if it is, under what temperature, pressure, etc?

The general consensus is that carbon is unique in its ability to form stable chains, to bond to a variety of other 'useful' atoms (e.g. N,O), and to form stable double bonds, all of which are central to life. There is some useful speculation at http://en.wikipedia.org/wiki/Silicon_based_life#Silicon_biochemistry

This is more of a chemistry than a biology question. You are basically asking what other element has similar bonding capabilities as carbon and could be used to form the chemical backbone of complex macromolecules. Maybe you should try your luck at Chemistry.SE

I've found also a book on astrobiology, but still don't know if it's gonna be useful.

OK, I'll bite...

One thing that hasn't be mentioned and should is that there is no consensus on how to define what life exactly is. Basically, all known life form is carbon-base, so say you would find some other "life-form" that is not carbon-based, how would you even tell if it is alive?

@Bitwise But isn't there a consensus on what is it?

@GustavoBandeira the consensus is that what is "similar" to what we define as alive is also alive (of course you have to agree what "similar" means). The problem is what happens when you consider something which is a bit different than what we know... This is a well-known problem. For example check Wikipedia or any other place.

For the time being, I think the best bet is to regard things as life if they look like life as we know it on Earth. It is dreadfully anthropocentric but at least its a starter until  we really understand what separated living from non-living.

This is an interesting question, particularly considered in the context that Cairns-Smith (1985) even suggested that clays (silicates in solution) may have had some sort of early selection acting on them due to their surface chemistries.
However, there are a number of major problems with Silicon. Some are chemical and some are astrophysical in nature. For example:

Silicon has a lower electronegativity than carbon and a longer bond length. Silicon can polymerize, but many conformations (such as rings) are highly reactive or unstable.
Silicon lacks chirality. Since biochemical reactions are very specific this may present a fundamental problem for alien biochemistries.
We don't see silicon macromolecules in nature. Large carbon molecules are seen in space such a polycyclic aromatic hydrocarbon rings. The largest silicon molecule seen in space is a chain of SiC_3 (and maybe SiC_4).
On reacting with oxygen (which it does readily) silicon likes to form solids like sand.
Silicon is much less common than Carbon in the Universe. The Solar abundance of silicon is 1/10 that of carbon, and supernova yields suggest that the silicon abundance may be as low as 1/100 that of carbon during nucleosynthesis in low/intermediate mass stars.

To form complex silicon molecules we would probably need to keep it in an oxygen-free environment and somehow maintain it in solution. One possibility would be to hold it at high pressure and temperature such as in the interiors of planets (think deep hot biosphere theory) but this presents another host of problems for conceivable biochmistries and is very speculative.
Apponi, A.J., McCarthy, M.C., Gottlieb, C.A., & Thaddeus, P. 1999, Journal of Chemical Physics, 111, 3911
Cairns-Smith, A. G. (1985) Seven Clues to the Origin of Life  Cambridge University Press, New York, ISBN 0-521-27522-9.
Woosley, S.E., & Weaver, T.A. 1995, Astrophysical Journal Supplement, 101, 181

It's an interesting question. However I suspect we'll be finding lots of weird carbon-based slime rather than anything silicon based. However,  it's a big Universe out there!

I was thinking about another environmental condition where it could happen, but I have no idea if such a thing would be possible.


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How would ecology be affected if 100km² of an ocean surface was covered by a floating object?
Assume that we planted floating solar cells on the ocean surfaces. Assume a 100km² solar cell field in the middle of the Pacific Ocean. All of the sunlight will be blocked by them. How would that affect the life in oceans?

It might, however, result in an increase of macrofauna, especially if the solar plates were anchored somehow at the bottom of the ocean. This may seem paradoxical, but for most groups of sessile macrofauna (cnidarians, tunicates, bryozoans, brachiopods, some molluscs, and so on), the limiting resource in the ocean is space, and any solid or semisolid surface is a good surface to live on, so at least along the margins of the solar plates, we should expect to see enormous amounts of macrofauna, in the same way as we see lots of it on the keels of ships, on jetties, oilrigs, and all other man-made structures in the sea.
I would expect that once such a sessile community is established, it would be beneficial to other organisms as well. Many polychaetes, molluscs, arthropods, and other groups are predators of the sessile community, and as the larval stages are often planktonic, I would expect to see these established in this community as well, given time.
This could in turn attract fish, especially if the platform is not too far from land, and is not cleaned, but the various shells and structures built by the sessile community is allowed to remain even after the actual organisms die off. The spaces between and inside dead sea shells are often very important places for egg deposition by fish, which may or may not remain in the area when they grow up.
Now, if the solar plates were divided into smaller connected discs, so that there is sunlight reaching the water between the discs, this margin effect would be even more profound, I would expect, as there would be sessile macrofauna around all the margins, and if sunlight comes down between the discs, that would allow some primary production even within the solar field.
So while rg255's answer is certainly also correct, I do not think the situation is necessarily as bleak as depicted in that answer, however, it would all depend on how the structure is built and maintained. Dividing the solar panels into smaller, connected units would be much better than having one solid platform (I assume this would be true also for mechanical and engineering reasons, but I'm not an engineer...), and there are certainly other ways to reduce the impact of such a solar system platform.
I would also guess that any platform placed in the middle of the ocean would have to include some system for keeping oceanic birds away.

I tend to disagree a little.  If anchored, i would think that the dead spot in the middle would still be about 5 km away from any lighted portion of the sea. that's quite a perturbation.  Filtering organisms in the middle of the array would not get so many nutrients, would they?

The vast majority of light only penetrates the top 200 metres of the ocean, the euphotic zone, so your answer is roughly "what ever lives in the euphotic zone which requires light." In all likelihood I would expect this to cause:

anything  which is not highly mobile but, is dependent on sunlight (phytoplankton etc.), would die.

the more mobile ("free swimming") which rely on either sunlight or the (now dead) slower resources would move out of the area.

reduced flow of nutrients in to the lower parts of the ocean - biomass from the upper regions dies and sinks to the lower levels, if it no longer grows in the upper 200m then there will be less down flow after time.

Overall, the impact would be low because the area of the pacific is >165,000,000 km2 so the density of biota would only increase marginally in the top 200 metres of the pacific (the sunlit water volume decreases from 33,040,000,000,000 cubic metres to 33,039,080,000,000 cub. metres). Also, if we assume that the platform is free floating that means it would drift thus only causing short term loss of sunlight for the less mobile organisms.
EDIT:
Upon reading @Kotatsu's answer I feel they have made a very good point and I should add the following:
By providing a solid surface it could also benefit oceanic life by increasing area available to live for sessile organisms (just like shipwrecks, oil rigs etc.). Further if the panels were broken up (I assume this would be the likely design because sitting a huge sheet across the ocean will leave it prone to twisting by wave motion) light would be able to pass between the gaps. I agree with @Kotatsu, and this "floating panel" could even be beneficial to the ocean ecosystem.

note: I am not an expert on this so it is purely an application of logic and my best guess


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Modern reference for Kropotkin's lazy bees
I have been reading through Peter Kropotkin's Mutual Aid: A Factor of Evolution and he mentions a curious fact about bees (bolding by me for emphasis):

predatory instincts and laziness continue to exist among the bees as well, and reappear each. time that their growth is favoured by some circumstances. It is well known that there always are a number of bees which prefer a life of robbery to the laborious life of a worker; and that both periods of scarcity and periods of an unusually rich
  supply of food lead to an increase of the robbing class. When our crops are in and there remains but little to gather in our meadows and fields, robbing bees become of more frequent occurrence; while, on the other side, about the sugar plantations of the West Indies and the sugar refineries of Europe, robbery, laziness, and very often drunkenness become quite usual with the bees. We thus see that anti-social instincts continue to exist amidst the bees as well;

He does not provide a citation for this (and even if he did, it would be something from the late 1800s). Is there a good modern reference for the above behavior?
I would in particular be interested in something like a graph of %-robber-bees vs. plentiness-of-food (in some abstract measure of the latter) so that I could intuitively see the increase in lazy/robber bees as the environment is low on food, or as it is overly abundant and compare it to 'typical levels'.
Theories that explain this behavior are of interest, as well, but I am primarily after experimental measures/observations to support and quantify the above quote.

Can you define what you think he means by Robbery? Is it robbing from the plant or raiding other colonies?

@niallhaslam that is his full treatment of the subject. He says nothing more on it in terms of defining things.

@niallhaslam I think we can assume that he's referring to what we would call today "cheat" or "selfish" individuals, rather than nectar robbers.

The quote refers to 'robber' bees, but in today's terminology, there are actually three separate phenomena. "Cheating" in bees and other social animals refers to the exploitation of a social contract for one's own benefit. Example: bee workers lay their own eggs rather than tending those of the queen. "Laziness" or "inactivity" of bee or other social insect workers is incredibly widespread, but it is not clear that it is selfish: it may be a side-effect of imperfect task allocation, or those individuals may be a reserve work force. "Robbing" in bees usually refers to removal of nectar or pollen from flowers without pollinating them.
"Cheating" associated with illicit reproduction is widespread in social insects, including in bees, and there's a broad literature on it (search terms "anarchist" "queenright", "policing") but it sounds like your question concerns differential effort and environmental resources specifically.
Differential effort in labor ("laziness vs. busynesss") has been seen in many social animals. The way you frame the question seems to be in terms of:

"how many lazy individuals can a society tolerate given environmental
  conditions?"

Most observational/experimental studies seem to have approached the question in terms of:

"how can what appears to be cheating actually be adaptive?"

For instance, Kukuk et al. suggest that in Halictine bees, lazy bees who avoid the high-mortality-risk foraging tasks are actually acting as caretakers and orphan-rearers for the brood of the foraging busy bees. It's also been proposed that apparently lazy insects act as a "defensive reserve" for the nest, although at least in Bombus impatiens, experiments show no evidence that lazy bees defend any more than busy bees (Jandt et al.)
Lazy individuals could also be acting a labor reserve ("substitute helpers"), in case of food or colony depletion. To me, this scenario is the closest to what you mention – the idea that lazy individuals become busier, either voluntarily or through coercion, in time of need. Baglione et al. show that this is the case for carrion crows, and quantify it to some degree along the terms you suggest. On the other hand, Cartar (cited in Jandt and Dornhaus) shows that for a number of bumblebee species, it was more likely that busy bees would work harder or switch tasks than it was that the lazy bees would become busy!
In sum, what you/Kropotkin suggest exists in all social insects, although the mechanisms of sociality and of laziness are diverse and various among species.

 Baglione V, Canestrari D, Chiarati E, Vera R, Marcos JM. 2010. Lazy group members are substitute helpers in carrion crows. Proc Biol Sci 277: 3275–3282. (free)
Cartar RV. 1992. Adjustment of foraging effort and task switching in energy-manipulated wild bumblebee colonies. Animal Behaviour. (full text not online?)
Jandt JM, Robins NS, Moore RE, Dornhaus A. 2012. Individual bumblebees vary in response to disturbance: a test of the defensive reserve hypothesis. Insectes sociaux. (behind paywall, buy Jandt kindly has uploaded for free on her site)
 Jandt, Dornhaus. 2009. Spatial organization and division of labour in the bumblebee Bombus impatiens. Animal Behaviour 77: 11–11. (behind paywall, but also free on Jandt's site)
Kukuk PF, Ward SA, Jozwiak A. 1998. Mutualistic benefits generate an unequal distribution of risky activities among unrelated group members. Naturwissenschaften. (Behind paywall, but this free article by Forbes et al. reports similar information)

Also see:
Jandt JM, Dornhaus A 2011 ‘Competition and cooperation: bumblebee spatial organization and division of labor may affect worker reproduction late in life’, Behavioral Ecology and Sociobiology 65: 2341-2349.
- shows that selfishness/cheating may actually play a role
Dornhaus A, Holley J-A, Pook VG, Worswick G, Franks NR 2008 'Why do not all workers work? Colony size and workload during emigrations in the ant Temnothorax albipennis' Behavioral Ecology and Sociobiology 63: 43-51
- this paper reviews other literature about how many bees/ants in a colony are lazy; up to 75% or even more at a time!


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External sensory stimuli that awaken a person from sleep
An external sound or touch can awaken someone.
Can a light? It would have to be very strong, but part of the reason might be that it would have to penetrate the eyelids.
And can a smell or taste?
When we are awake, the impact of sensory stimuli and of changes in them depend on which sense is stimulated.
My question concerns the kind and strength of impact the stimulation of each sense has when we are asleep, in relation to what is needed to wake us up.
Note
Thanks to @Mithoron for linking to another question, asked on this website by @Taladris. That question is certainly quite similar to this one and its answer contains some relevant material, even if the answer is not of high quality because of course our senses are "dimmed" when we are asleep and of course it is not true that "that we respond to our own names in a similar fashion in sleep and in wakefulness". The present question asks specifically about awakening because of sensory input. I believe I am sometimes awakened by smells, although it is hard for me to tell whether or not I am right. Part of my question asks for views or facts concerning whether people can be woken by smells at all. This is different from asking whether we can smell when we are asleep.

possible duplicate of What senses are active while sleeping?

This is not a duplicate in my opinion, as anongoodnurse's answer on the linked question doesn't address vision.

Can someone please remove the box saying "This question may already have an answer here". I have now edited to explain why this question is different.


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Are there single-celled organisms that have evolved from multi-cellular ones?
I'm reading this paper about transmissible cancer cells in clams (Metzger et al. 2015) and I was wondering if there are any single-cellular organisms that are around today that are suspected as having descended from a multicellular organism
My question is different from this question as I'm not asking about cancer specifically but rather single-celled organisms evolving from multicellular organisms in general.

Related Post: I am not sure if I can call this a duplicate.

@WYSIWYG I think the answer in the related post answers this question, but the question is different. Not a dupe question, therefore, if you ask me. Given the quality of both questions and answers I would definitely not vote for close as dupe

I would consider HeLa cells to be an example of a unicellular eukaryotic organism that evolved from humans. It can survive independently and replicate within cell culture plates, but cannot survive in the wild, however.

HeLa cells are, like in your example, cancer cells, in this specific case human cervical cancer cells. They were propagated as an immortal cell line, and completely match the replication characteristics of eukaryotic cell lines when propagated in the laboratory.
It can be even considered the case that HeLa cells are actually a kind of unicellular eukaryotic model organism not unlike S. cerevisiae, since they are widely used in experiments involving human-like cells.
As WYSIWYG has said in the comments, some biologists have even assigned the binomial name Helacyton gartleri to the cells (albeit with some controversy).

Hela cells have a scientific name: Helacyton gartleri. They are classified as a separate organism because they can grow beyond human control and have chromosomal differences compared to a normal human cell.

@AliceD http://en.wikipedia.org/wiki/Directed_evolution

Great answer and thanks guys for explaining. +1 here!

Excellent, this is very interesting, especially that some biologists consider them to be a separate organism. Very interesting that they can survive in culture. I'm wondering if there are other examples (discovered or undiscovered) of single cells that broke off and can survive in the wild

great perspective, thanks for sharing! also, thanks go to @WYSIWYG

@MarchHo Thanks for adding that the classification is in some controversy.

This is very interesting, but the OP only contextualized this with cancer. The question seems to instead be about natural occurrences of reversion from multicellularity to single celled organisms. (The Tasmanian devil answer is more along the lines of the question posted, despite being in the context of cancer.)

Inspired by the answer by @MarchHo, I came to think of the contagious cancer that attacks Tasmanian Devils - Devil facial tumour disease - which should provide a very similar example to the clams in your question. I don't think it has been given a species name though, but for most purposes it functions as an independent species. This "organism" lives as a parasite on Tasmanian devils, but has originated from a cancer tumour in an individual Tasmanian devil. You could maybe argue that it is not single-celled, since it develops into tumours, but it most likely spreads as single cells and I suspect that the cells functions as independent entities. However, I don't know enought about the disease to really say if e.g. cells in the tumours differentiate into different types. The cancer is spread by bites, and only affects Tasmanian devils (see http://www.tassiedevil.com: The Disease). This disease is apparently one of only three known cases of contagious cancers (also in dogs and hamsters), but this is maybe 4 now if the clams are a similar case).

(picture from Wikipedia)


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Can one eye affect the other eye's low-light adaption?
This previous question addresses how long eyes need to adapt to darkness and reach full contrast. My question is how does one eye affect the "transition" and/or efficacy of this "night vision" of the other eye? Specifically:

Are the eyes' adaptation to darkness linked or is it possible for one eye to transition to "night vision" while the other does not?
Would exposure to bright light in one eye slow the other eye's progression toward being adapted to low light?
If one eye had transitioned to low-light vision, can light exposure to the other eye reduce the ability for the first eye to see effectively in low light?

I understand that the dark-adaptation of eyes seems to occur primarily at the rod and cone level, but I'm wondering if perhaps over-stimulation from bright light in one eye would have a saturating effect on the signal being sent to the primary visual cortex (and thus impact the dark adaptation)?

Yes, but not in a really effective manner. Two things occur for an eye to switch to "night mode". The most influential change is that of seeing mainly with the "rod" visual receptors, as you noted. The second, relatively minor change is that of pupil diameter. In the dark, the iris constricts to produce a larger pupil, allowing more light into the eye. This can be done very rapidly, which is why any interruption in this mechanism is negligible.
The important piece of information you need to know is that for most people, each eye's iris acts sympathetically to that of the other. This means that if I were to shine a pen light into your right eye, causing your pupil to constrict, your left eye will do the same, even if no light is entering that eye.
So, if you were to wear an eyepatch over your left eye in a brightly-lit area, and then enter a dark room and remove the eyepatch, you would have far better vision in your left eye because that eye is operating primarily with rods. To answer your question, there was a tiny setback caused by the right eye in terms of pupil diameter, but this would be corrected within a fraction of a second.
Regarding your inference as to a "saturation effect", the answer is yes and no. If you were to wear contacts, with the lens covering the left eye being tinted dark and the lens on the right being clear, then at first it would appear that the light entering the right eye is affecting the vision of the left. This is simply a matter of focus, though. You're distracted by the larger amount of information that needs to be processed coming from the right eye. With proper focus, however, you would see that the left eye is operating independently in terms of light adaptation (aside from pupil diameter, as mentioned).
I hope this answers your question
Edit
I've been asked to add references. I'll not provide a reference for the use of rod receptors in low light as you have already acknowledged this fact, but I will provide a reference for the simultaneous pupil dilation. For the saturation effect, you can easily prove this to yourself at home. Skip the contacts and pop one lens out of a dark pair of sunglasses.
https://en.wikipedia.org/wiki/Pupillary_light_reflex

Can you please add some references.

Done. If you need more, let me know.


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How would a warm winter affect maple sap production?
The past winter (2011-2012) was warmer than usual.
Trees are normally tapped in late February when the daily maximum temperature goes above freezing. However, assuming that there have been relatively few days with a maximum temperature below freezing, how would this affect the timing and quantity of sap flow?

This article has a clear explanation (backed up by good links) of the effects of climate change on maple sap production, including the following:

Maple trees produce the best sap on cool days preceded by freezing nights – the cold weather causes the sap in the tree to freeze, creating a low-pressure vacuum that draws more sap up from the roots. When temperatures rise the next day, the sap melts and oozes through the tree, making for easy collection. When temperatures stay abnormally warm, as they have been lately, this process does not occur.
Additionally, the warm weather causes the trees to begin to bud.  The hormones that trigger budding also decrease the sap’s sugar content and spoil its taste. This means that it takes much larger quantities of sap to boil down to a gallon of syrup.


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Could someone recommend a book for surveying species?
I'm trying to get/renew basic knowledge of species. Could someone recommend a book for surveying "important"/"representational" species? I am looking for a book with good illustrations and that covers most "important"/"representational" species.
I am currently reading The Tree of Life: A Phylogenetic Classification, and it is thicker than I want to read as a first book in this kind.

The book you are using is the one I was going to recommend. With perhaps 8.7 million species (http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001127), there is no short route.

If you are OK with a web solution, this answer (http://biology.stackexchange.com/a/395/107) might be useful.

Most general surveys of species I've seen (in school, for instance) tend to go through the phyla (for animals) and the divisions (for plants) and looks at the general characteristics of each group. Would that be sufficient for your needs?

Yes.  That will be sufficient for my needs.

Judging from your response to Gurav in the comments, it sounds like introductory zoology and plant biology texts would fit the bill.
For zoology, we teach from Hickman et al's Integrated Principles of Zoology. It outlines the major phyla, their defining characteristics, with plenty of specific examples scattered throughout. There are nice little problem sets throughout, and it goes into a solid amount of detail for a first or second year zoology course.
For plants, I've used Graham et al's Plant Biology, which takes a similar general approach. Though it's perhaps a bit broader, and less species-focused.
Both of these books outline the major relevant groups, and use 'representative' species to illustrate various biological points throughout. They might be a good place to start!


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What type of photosynthesis is performed by phytoplankton?
I am not a biologist, but I know there exist three variants of photosynthesis, namely C3, C4 and CAM.
I would like to know what type is used by the ocean's phytoplankton? It might also be that different photosynthetic mechanisms are used by the bacteria vs. algae. I have searched the web, but the information I find is too broad.

I'm not sure that all phytoplankton perform the same type of photosynthesis.
Originally, people thought that they all performed C4, on the basis of genome sequencing, which revealed the presence of genes important for C4 photosynthesis.  However, experiments on individual species seemed to indicate that the phytoplankton were performing multiple types of photosynthesis (source).
EDIT: CAM is unlikely, as that is an adaptation for dry environments.
EDIT 2: and of course, some phytoplankton appear to have both C3 and C4 pathways. In short, you can't generalize.

Some wires crossed here.  Most algae are C3, in other words they use the Calvin cycle to fix CO₂. Another way of saying it is that RUBISCO (Ribulose bisphosphate carboxylase) is dorectly responsible for CO₂ fixation.  There is some evidence (disputed) that some diatoms use a form of the C4 pathway in which CO₂ is initially fixed as a 4-carbon compound (CO₂+C3 → C4).  The C4 compound formed is often malic acid.
Trying to establish if the C4 pathway is functional for carbon fixation is not easy.  Genomics can be misleading. Practically all photosynthetic organisms have the genes required for the C4 pathway but whether they are expressed is another matter (look at KEGG).  C4 photosynthesis usually requires complex anatomy because it is essentially a CO₂ supercharger mechanism because the C4 carbon form is then decarboxylated in a special location to provide RUBISCO with a very high CO₂ environment to finally fix CO₂ a 2nd time and pass the two C3 carbon compounds formed from CO₂ plus Ribulose Bisphosphate into the Calvin cycle.


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Salmon returning to lay eggs
To spawn, salmon return to the river in which they were born. Is it because the individuals remember the specific river, or because populations are genetically conditioned to follow specific environmental cues that guide them to the specific river?
In other words, if a salmon is artificially taken to lay eggs in a different, ("wrong") river, will its progeny return, when grown, to the river where they were born, or that where their mother was born?
If salmon that was grown in a fish-farm is taken to the sea, does it return to a river? How does it choose which?

Answer
The mechanism for salmon natal homing isn't exactly known, but there are really two good hypotheses out there.

Salmon have an extremely good sense of smell. One hypothesis is that they retain an imprint of their birthplace's odor, and manage to recognize it again at a later time (as explained by this article).
Another hypothesis: the Earth's magnetic field guides the salmon to their birthplace via geomagnetic navigation. They then use chemical cues to recognize the stream in which they were born (supported by this scientific article).

These hypotheses were mentioned in this Wikipedia article. Note that there was a third pheromone-related hypothesis which was disproved (as shown here).
I would say that both memory and "genetic conditioning" could potentially be factors in how these animals perform this natal homing, among other things. However, it is difficult to pinpoint which one if any, because neither hypothesis has yet to be confirmed, and both function on completely different mechanisms. Not to mention that we can't tell what exactly a fish is thinking, and also what chemical we're looking for, if there is one.
Finally, for your personal information, salmon aren't the only animals to do this: sea turtles return to their birthplace as well.
TLDR: If a salmon was displaced right before birth, or birthed in a pool, I would imagine it returning to that particular location at sexual maturity.

References

Lohmann, K. J., N. F. Putman, and C. M. F. Lohmann. “Movement Ecology Special Feature: Geomagnetic Imprinting: A Unifying Hypothesis of Long-distance Natal Homing in Salmon and Sea Turtles.” Proceedings of the National Academy of Sciences 105, no. 49 (December 5, 2008): 19096–19101.

Dittman, A., and T. Quinn. “Homing in Pacific Salmon: Mechanisms and Ecological Basis.” Journal of Experimental Biology 199, no. 1 (January 1, 1996): 83–91.

Black, Geoff, and J. Dempson. “A Test of the Hypothesis of Pheromone Attraction in Salmonid Migration.” Environmental Biology of Fishes 15, no. 3 (1986): 229–235.

I don't understand how those two hypothesis answer the question. They provide a mechanism for how to find their way back, but it doesn't answer if a given salmon has a genetic predisposition for going towards a certain spawn-site smell or if it remembers it from its' hatching. Both mechanisms could be consistent with either of the OPs interpretations (although the memory version makes more sense), can you explain why you think both these mechanisms operate interdependent of memory or genetic conditioning?

Hmm, I can see what you mean. I've edited the answer slightly. Please let me know if I've solved the problem or what else can be changed. :)


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Has there been any observation of species adapting the evolution process?
I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment.

Nick's answer here is a bit off base. You could look at cells of the immune system as doing something similar to evolving (there is selection, etc.). But these changes are not passed on to progeny through the germ line.

I think humans have changed their reproduction age back and forth several times during their evolution. I recall hearing about geographical differences for entry into puberty age as well.

Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).

The "change in reproduction age" you mention is one major aspect of life history evolution.
A massive literature exists on this topic, including several books: e.g., The evolution of life histories: Theory and analysis (Roff, 1992) and The evolution of life histories (Stearns, 1992).
Reznick and various colleagues have carried out extensive studies of experimental life history evolution in Trinidadian guppies going back ~30 years. For example:

Reznick, D.N. and Endler, J.A. 1982. The impact of predation on life history evolution in Trindadian guppies (Poecilia reticulata). Evolution 36:160-177.
Reznick, D.N. and Bryga, H. 1987. Life-history evolution in guppies. 1. Phenotypic and genotypic changes in an introduction experiment.  Evolution 41:1370-1385.
Reznick, D.N. 1989. Life history evolution in guppies. 2. Repeatability of field observations and the effects of season on life histories. Evolution 43:1285-1297.
Reznick, D.N., Shaw, F.H., Rodd, F.H. and Shaw, R.G. 1997. Evaluation of the rate of evolution in natural populations of guppies (Poecilia reticulata).  Science 275: 1934-1937.
Reznick, D.N. 1997. Life history evolution in guppies (Poecilia reticulata): guppies as a model for studying the evolutionary biology of aging. Experimental Gerontology 32:245-258.

Life history evolution has also been documented in response to human pressures. Fisheries stocks are evolving in response to overfishing. For example:

Walsh, M.R., Munch, S.B., Chiba, S. and Conover, D.O. 2006. Maladaptive changes in multiple traits caused by fishing: impediments to population recovery. Ecology Letters 9:142-148.
Conover, D.O., Arnott, S.A., Walsh, M.R. and Munch, S.B.. 2005. Darwinian Fishery Science: lessons from the Atlantic silverside. Canadian Journal of Fisheries and Aquatic Science 62:730-737.

I think this falls into your criteria but correct me if i'm wrong :).
The HIV reverse transcriptase protein has evolved to have relatively low fidelity (leading to a high mutation rate in replicated virus particles).  Reverse transcriptase is also recombinogenic, ie. it can switch templates during replication leading to even more variability.  Combined, these two properties lead to each individual having a large number of variant viral genomes, which leads to increased resistance to antiretroviral drugs etc.
EDIT:
I thought of influenza as a second example.  The viral genome has evolved to be fragmented into 7-8 pieces of RNA, which can be swapped with other strains during co-infection of a single cell.  This can lead to more virulent or transmissible strains of influenza; these can also be helpful to create new strains that influenza vaccines are no longer useful against.

Species have been observed in controlled experiments to use different sources of energy, for instance axenic E. coli cultures picking up citrate metabolism in Lenski's Lab at MSU.  They have also shown that mutations to the mutator gene mutT can accelerate the process of evolution, though it's evolution directed by fitness in a very specific setting.

How about species actively changing the factors that play a role in the selection process?
Humans are a species that have heavily modified this process. In the western world, we have gone away from selection by survival skills and genetic fitness to move to a social selection, where genome is secondary to social skills and adaptation to fashion, which are acquired skills.

I don’t think this entails a change in the underlying mechanism. At least, not one that has been demonstrated yet. “social selection” is a very diffuse term. Does it actually differ from natural selection? Personally, I doubt it: it can be readily explained in terms of natural and sexual and kin selection so this would be the most parsimonious explanation.

Pigliucci gives a good review of some aspects of this topic in "Is evolvability evolvable?" (2008). He sees what you're asking about, which he calls "evolvability", as one of the key topics for the future of the study of evolution.
It's very conceptually dense evo-devo-theory, so I'll probably do a poor job trying to explain it, but he tries to set up a framework that deals not just with things like life-history (per kmm's answer) and mutation/recombination rate (low fidelity in HIV per GWW's answer, and, I suppose, the evolution of sex itself), but also with constraints that evolve at various levels to "positively channel" mutation (that is, the understanding that while mutations are effectively random, the phenotypes that emerge, and are acted upon by natural selection, are not random, but are channelled by the developmental system of the organism).
He also includes the role of development in opening up "phenotypic space" into which a lineage may evolve. For instance, single-celled organisms have a limit on size and complexity, the evolution of multicellularity opens up this huge zone of evolvability. In a sense, this is also the "evolution of evolution".

 Pigliucci M. 2008. Is evolvability evolvable? Nat Rev Genet 9: 75–82. Behind paywall, but free pdf here

If you look at the adaptive immune system, the process of B-cell recombination, clonal expansion and somatic hypermuation is, in essence, induced evolution.

The following paper published on August 25, 2015 claims that there are indeed directed mutations.
Evidence for Retromutagenesis as a Mechanism for Adaptive Mutation in Escherichia coli
http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005477


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How do white Caladiums perform enough photosynthesis to support their mass?
In some white caladiums, there is less than a square inch of green space spread over the whole leaf. How do these plants perform the photosynthesis necessary to support the large leaves, the roots, the flowers, and build a corm?

There are many different kinds of plants that have independently evolved this sort of variegation (non-green areas) in the leaves. However, the mechanisms by which they effect this vary between species.
Some have little or no chlorophyll in the non-green areas, but many others have changed the architecture of their leaf cell layers in the non-green areas, creating refraction effects that make the leaves appear white, but don't significantly change their photosynthetic efficiency (Sheue et al.) In fact, Arum italicum white areas actually have higher efficiency in certain light conditions! (La Rocca et al.)
I can't find any information on which type of variegation Caladium shows. The genus Caladium is related to the Arum I mentioned above which uses the "architecture" method, but it's also related to Epipremnum, which seems to use the "no-cholorophyl" method.
Sheue et al. mention that with some species that use the architecture method, using transmitted light instead of reflected light reveals that the white spots are actually green; while in no-chlorophyll plants the spots remain white. If you have a Caladium around, you could try holding its leaf up to a bright light, and see!
So, to answer your question: if Caladium is an 'architecture-variegation' plant, its white areas perform photosynthesis at or near the efficiency of the green areas of the leaf. If it's a 'no-chlorophyll-variegation' plant, it would have reduced efficiency, but might make up for this with strategies including:

Having a larger total leaf area (La Rocca et al. and also see this question)
Only developing large white areas if there's plenty of light as they grow (Garland et al.)
Increasing the mitochondrial activity in its white areas, which could lead to other energy efficiencies (Toshoji et al.)
Using Homo sapiens to help it reproduce and provide plenty of light for it. Many of these extreme variegation patterns are found in horticulturally bred varieties!
Just using its green areas for photosynthesis, and "accepting" the fact that the white areas are not producing energy. In natural populations, you often don't find varieties as completely white as in that picture: they usually show white spots and plenty of green. This is true of Caladium species in the wild, which may use the variegation to mimic and to prevent herbivory: potential pests think the leaves are already infested, and avoid them (Soltau et al.). In other words, even if the white patches represent decreased photosynthesis efficiency, it could be a trade-off in order to achieve less herbivory.

Garland KF, Burnett SE, Stack LB, Zhang D. 2010. Minimum Daily Light Integral for Growing High-quality Coleus. HortTechnology 20: 929–933.
 La Rocca NN, Rascio NN, Pupillo PP. 2011. Variegation in Arum italicum leaves. A structural-functional study. Plant Physiol Biochem 49: 1392–1398.
 Sheue C-RC, Pao S-HS, Chien L-FL, Chesson PP, Peng C-IC. 2012. Natural foliar variegation without costs? The case of Begonia. Ann Bot 109: 1065–1074.
 Soltau U, Dötterl S, Liede-Schumann S. 2009. Leaf variegation in Caladium steudneriifolium (Araceae): a case of mimicry? Evolutionary Ecology 23: 503–512.
 Toshoji HH, Katsumata TT, Takusagawa MM, Yusa YY, Sakai AA. 2012. Effects of chloroplast dysfunction on mitochondria: white sectors in variegated leaves have higher mitochondrial DNA levels and lower dark respiration rates than green sectors. Protoplasma 249: 805–817.

Any free growing (non parasitic) plant will rely on photosynthesis.
Plants do not have to be green though. It says in this article that the white caladium has chlorophyll, but relatively little, or the white color may come from other pigments that reflect other kinds of light.

“As with other white caladiums, there’s a little bit of mystery surrounding Florida Moonlight,” Miranda said. “Where’s the chlorophyll? Chlorophyll is a pigment that caladiums and other plants use to produce food by photosynthesis, and it gives the leaves their green color. White caladiums either get along with very little chlorophyll, or they somehow conceal its presence

And my question is, how does it maintain itself with so little chlorophyll. I know that it does already.