Wikipedia:Reference desk/Archives/Science/2012 March 23

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March 23

Are there any plant species that mimic the appearance of surrounding flora

I`m a writer and a short story I`m working on at the moment concerns an ailing elderly biologist or naturist discussing with his daughter the nature of his work many years ago, much of it centering on a particular plant. I have a marvelous idea for the story that involves this plant being able to mimic things around it, and I`m wondering if there is any actual scientific basis I could base my work of fiction on. I`d like to know if there is any plant or species of flower in existence that changes its appearance or growth process based on what other flora surrounds it.173.34.250.152 (talk) 00:18, 23 March 2012 (UTC)

I don't think any can do that, as that would require eyes, to know what the plants around them look like, but some plants do mimic poisonous plants, etc., so they won't be bothered. I do have a story you could perhaps adapt to your purposes, though. I call it my "evolutionary mold" story. One unfortunate bathroom where I lived had all pink tile. Whenever I spotted any mold, I killed it. However, I eventually found pink mold down on the white tub, and concluded that there must also be pink mold up on the pink tiles, but which I was unable to see and thus didn't kill. Therefore, that color mold survived, while I killed off the rest. I had thus unintentionally caused pink mold to evolve (technically it's likely not evolution, only variation within a species, as in the case of the peppered moth). StuRat (talk) 03:13, 23 March 2012 (UTC)

I agree with StuRat - the main evolutionary selection agents on plants are small herbivores (insects) and they tend to focus on chemical rather than visual cues. There are however a few strange visual mimicry subsystems though - like false eggs on the leaf that prevent lepidoptera from laying "another" and some human selected examples like Vavilovian seed mimicry. Shyamal (talk) 04:02, 23 March 2012 (UTC)

No no no! Stu! Come on ;) If you are a plant, You definitely do NOT need eyes to evolve mimicry, think about it, it's your predator that will make the selection for you :) I'm not saying I disagree with your conclusion, but I definitely don't believe it's because plants don't have eyes. Vespine (talk) 04:10, 23 March 2012 (UTC)

I'm struggiling a little to get my head around this completely. I wonder if plants DO evolve mimicry sometimes but we just find it hard to recognize because they are all so passive and so many plants are quite similar to begin with. Now, I haven't heard of the above example, but if some plants have evolved to look like poisonous plants, well, that's precisely what mimicry is, it's what Mimic_poison_frog does. I don't believe that frogs eyes have anything to do with the fact it evolved to look like a poisonous frog. Vespine (talk) 04:18, 23 March 2012 (UTC)

You interpreted the Q differently than I. I read it as asking if a single plant can do like a chameleon and change to match it's current environment. To that I said no, but suggested that a plant species evolving to mimic another, over generations, is quite possible. StuRat (talk) 04:24, 23 March 2012 (UTC)

Sorry yes, maye I didn't quite comprehend your reply.. Vespine (talk) 04:55, 23 March 2012 (UTC)

(edit conflict) × over 9000! Indeed. Plenty of marine animals for example, without eyes, with very rudimentary eyes, or blind to certain colors can still exhibit highly elaborate mimicry or coloration. The environments usually dictate the evolution of crypsis and similar behavior, not the species themselves. With exceptions to humans and other animals displaying signs of intelligence of course (e.g. the mimic octopus).

While I agree that I don't think there are any plants that exhibit metachrosis, there are plenty of plants that mimic animals which they definitely can not see. In addition to Passiflora mimicking insect eggs already mentioned above; some orchids of the genus Ophrys, aside from broadcasting pheromones similar to females of certain wasps, also tend to have flowers that have structures similar to the actual female wasps in question. Bamboozled males will try to mate with them, in doing so pollinating the flowers. Plants which target the same pollinator/disperser species also often have flowers or fruits that are the same color or shape. Plants inhabiting similar environments develop the same adaptations (e.g. Euphorbia obesa and Astrophytum asterias). Plants might resemble rocks or their young leaves might resemble dead leaves. Though the latter examples are not exactly mimicking other plants, as they're either mimicking animals/environments or are examples of convergent evolution.

And anyway, the answer is yes. Plants mimic plants. The most obvious I can think of is the cryptic mimicry of certain mistletoe species (e.g. Dendrophthoe spp. and Amyema spp.). They imitate the leaves of their host plants to be less noticeable and avoid predation. See the pictures here.

Some plants also develop structures that look like thorns but aren't actually sharp. Others exhibit automimicry of aposematic colorful thorns like Aloe and Agave which mimic their own thorns on parts of them that do not actually have thorns (like their serrated imprints or flecks of colors on their leaves), or the leaf buds of roses which look superficially like thorns when young. But yes, plants are probably more likely to engage in "chemical warfare" than visual ones. It has been suggested that non-toxic plants might imitate the flavor or odor, or both of toxic plants as a form of Batesian mimicry. -- OBSIDIAN†SOUL 05:18, 23 March 2012 (UTC)

(ec) I don't have that good a knowledge of botany - I can't think of a case where a plant can choose to mimic multiple species depending on which is living nearby, but of course in biology you can never rule anything out. A single species mimic is the common vetch, which has adapted to mimic the lentil seed.^[1] so that farmers plant it unwillingly. Wnt (talk) 04:26, 23 March 2012 (UTC)

Rapid plant movement could make a good story perhaps... 84.197.178.75 (talk) 10:37, 23 March 2012 (UTC)

Another plant that mimics a single species is the White deadnettle that looks almost exactly like a Stinging nettle apart from having white flowers (and it doesn't sting). Alansplodge (talk) 18:30, 23 March 2012 (UTC)

Some mistletoe has leaves that are similar to the host plant. its complicated. Polypipe Wrangler (talk) 11:58, 25 March 2012 (UTC)

Percentage of Solution

If I take 10g of Potassium Sorbate, and dissolve it in 10g (10ml) of water, and the resulting solution is 20ml / 20g, what strength is the solution? Is it 50% or 100%? Thanks! 49.180.30.186 (talk) 00:27, 23 March 2012 (UTC)

Are you sure it is 20 mL total? But the question does not have a specific answer because "strength...%" can have more than one meaning. See Percentage solution for pointers to the various meanings. DMacks (talk) 00:31, 23 March 2012 (UTC)

Yes it appears to be 20ml total. But my literature doesn't specify whether my desired strength is w/v, w/w, or v/v? And I've read all three article on Percentage solution, and they just leave me more confused than ever, especially Mass_concentration_(chemistry)#Usage_in_biology. 49.180.30.186 (talk) 01:07, 23 March 2012 (UTC)

The situation is confused. That article describes a "100% potassium iodide" solution made up in a total volume of 100 ml. My opinion is that despite what the article says, the usage in biology is most typically by adding grams of solute to mls of solvent - at least at low concentrations, and I know I've seen it interpreted that way even at high concentrations in some instances. The theory here is that the worker simply wants instructions for what to mix together to get the desired solution, not a method that requires repeatedly remeasuring the volume and compensating with random decreasing amounts of solvent without going over. This is not the case for molarity, molality, or normality, which are genuinely determined within a total volume. There is so much confusion on the point, however, that when dealing with high percentages it may be best to look for literal instructions for a protocol just to be sure you and the other lab are really on the same page! Wnt (talk) 04:41, 23 March 2012 (UTC)

Speaking of which, [2] describes preparation of your solution as "50% potassium sorbate". Wnt (talk) 04:49, 23 March 2012 (UTC)

The article on potassium sorbate gives its solubility as 58.2% in water at 20°C. Those figures are usually w/v so I don't see how you could have dissolved potassium sorbate in water 1:1 like that without heating it. 203.27.72.5 (talk) 07:43, 26 March 2012 (UTC)

Utility of oil sands crude in the making of plastics

Hey - could anyone tell me if the synthetic crude oil produced via oil sands extraction is of any use in making plastics? Has anyone experimented with that yet? --192.234.2.90 (talk) 02:14, 23 March 2012 (UTC)

Synthetic oil and crude oil are two completely different things. Crude oil from oil sands is not much different to crude oil extracted by any other means, so I don't see why there would be any problem making the usual petrochemical plastics from it. Synthetic oil is a lubricant, not a raw material which you can get plastic from. Vespine (talk) 04:07, 23 March 2012 (UTC)

In some contexts, the term "synthetic" crude is used to refer to liquified heavy oil, which has more long-chain carbon than light oil - hence a heavier API weight. Oil from Saskatchewan oil sands, for example, may be "pre-cracked" or heated as part of the extraction process, so it flows better; this intermediate is the "synthetic" oil the OP refers to. It is not the same as synthetic oil in our article. In any case, it should be suitable for entry to a refinery, where the chemical engineers and the accountants will fiercely battle each other to determine whether a particular refined product is cost-effective to produce, on a given day, in a given region.

My favorite plastic, HDPE, is made by polymerizing ethene, which only requires two-carbons - you can crack anything to produce it. If you start with heavy oil, you can cook it for a very long time and produce ethene in scads, which would then usually go as a "raw material" to a separate petrochemical factory to be polymerized into plastics you're familiar with. As I mentioned above, if the refinery would rather use its long heavy hydrocarbons to produce industrial lubricants and diesel fuel (because they're more profitable), they might not justify productin of ethene in bulk quantitied; but some light product is always produced under almost all cracking conditions. Nimur (talk) 13:39, 23 March 2012 (UTC)

Help: Identify the Flowers

Please help in identify these flowers File:Purple-Yellow Flowers.JPG. Shrubs seen in Garden in India. Rajenver (talk) 06:46, 23 March 2012 (UTC)

Pansies, members of the viola species. These are a smaller variety. Richard Avery (talk) 08:15, 23 March 2012 (UTC)

Help: Identify the Flowers (Pink)

Please help in identifying the Flowering Plant. File:Pink Flowers - Shrub.JPG Rajenver (talk) 06:54, 23 March 2012 (UTC)

Phlox sp. Shyamal (talk) 07:24, 23 March 2012 (UTC)

A cultivar of Verbena. Phlox has a smooth edged leaf. If you look closely the leaves are slightly jagged along their edge. Richard Avery (talk) 08:42, 23 March 2012 (UTC)

Help: Identify the Flowers (White Flowers)

Please help in identifying the Flowering Plant File:White - Flowers in Garden.JPG Rajenver (talk) 06:55, 23 March 2012 (UTC)

Nerium sp. Shyamal (talk) 07:24, 23 March 2012 (UTC)

Help: Identify the Flowers / Plant

Help in identifying this flowering plant File:Flowing Plant with Pink Flowers and Buds.JPG Rajenver (talk) 07:08, 23 March 2012 (UTC)

Poppies of the papaver genus. The flowers are pink and the globe-shaped things with flattened tops are not buds but the seed cases. These look like annuals. Richard Avery (talk) 08:21, 23 March 2012 (UTC)

Good dyes for staining chromosomes

I've got an old lab guide for visualizing metaphase chromosomes (and cell nuclei) on onion root tips, where you use a heated HCl-orcein mix to break the cells and stain the chromosomes. I'd like to do this experiment with my students in high school, but I can't get my hands on any orcein. Any idea what other safe and inexpensive dye I could use?

Oh, and I'm in Finland, so all commercial options might not be available here. Thanks, --Albval (talk) 08:15, 23 March 2012 (UTC)

Well, the traditional method is a Giemsa stain. That's widely available and should be pretty affordable. Check out Sigma-Aldrich for instance, I'd be very surprised if they don't deliver to Finland. Fgf10 (talk) 08:55, 23 March 2012 (UTC)

Yes, I've been considering that. Problem is that we have to use our standard supplier for school that takes hideous prices for chemicals and takes forever to deliver. Therefore I'm hesitant to use a chemical I can't get from a standard pharmacy (should've said this before). I called my local pharmacy and they have methylene blue available, and cheaply too (so I could buy it w/ my own money). Any idea if it would do the trick alone and withstand the HCl used to break down the cell wall? --Albval (talk) 11:45, 23 March 2012 (UTC)

Ah, I've been at university labs so long I forget not all of us are as fortunate as having access to all sorts of sources for chemicals. Hmm, the methylene blue will definitely bind to the chromosomes (it's a component of the Giemsa stain anyway), but I'm not sure if the result will be as good as proper Giemsa. There must be a reason why people use Giemsa rather than straight methylene blue, but I couldn't tell you why (haven't done anything like this since undergrad). I'm sure there'll be someone along shortly to tell us! As for the HCl, I'm not sure you actually need that, as far as I can recall it should be enough to just let the cell spread dry to the air for a good while, should do the trick. For what it's worth, here's a random Google hit that agrees with my vague recollections. Fgf10 (talk) 12:42, 23 March 2012 (UTC)

Actually, forget about my HCL statement, you're using plant cells, so you'll definitely need some acid to break down the cell wall. Don't know about the the effect of low pH on methylene blue. Fgf10 (talk) 12:59, 23 March 2012 (UTC)

For an example of a methylene blue stain see File:Magnolia_petal_cells.jpg; not sure you'll be satisfied. Protonated methylene blue does have a different absorption peak (I've since added some stuff to the article) but once the wall is broken it's not getting repaired, so I'd think you could just wash out acid in any buffer. See [3] for a method of obtaining Azure B from methylene blue, if desired. Wnt (talk) 01:00, 24 March 2012 (UTC)

Places with the most living creatures per area

What places on Earth (or at least what general biomes) have the most living creatures (from single-celled organisms to plants to animals) per area? Square foot, square meter, whatever. My guess is that it'd be a rainforest somewhere, but does anyone have any insight on this or can you point me to any research/writing on this topic? Thanks. — Preceding unsigned comment added by 151.163.2.8 (talk) 12:54, 23 March 2012 (UTC)

We have some charts in Biomass (ecology) and primary production. Swamps, wetlands, and tropical rainforests rank high in grams of biologically produced carbon per square meter per year, which is as robust a method as any to quantify "most living creatures." If you want to count most number of individual organisms, you'll get into some murky water... colonial algaes and cyanobacterias are arguably a single individual, but it's reasonable and defensible to consider the same mass of pond scum as millions of distinct individuals, depending on how you define an organism. Nimur (talk) 13:10, 23 March 2012 (UTC)

This question is not as simple as it may seem at first. The way you phrase it- "most living creatures" makes it seem as though you are interested in the number of individuals. But perhaps you meant species richness. Even that gets complicated, because of species-area curves. For some purposes, richness is not even a good measure. Consider two farms. Both have 100 animals and four species. One farm has 97 sheep, 1 chicken, 1 pig, and 1 cow. The other has 33 sheep, 33 chickens, 33 pigs, and 1 cow. Which is more diverse? To tackle that, you need some other diversity index. So, the answer will change depending on which measure you are interested in. As a place to start, check out biodiversity hotspot. (Post WP:EC), Nimur raises good issues on individuals and biomass. I think you probably didn't really mean most number of individuals, but if so, please clarify. SemanticMantis (talk) 13:18, 23 March 2012 (UTC)

Tangentially related to your question, this is a very interesting article ("Dinosaurs of the Lost Continent") in the March issue of Scientific American Magazine. It concerns the capacity of land to support multiple species of very large animals. It particularly compares dinosaurs to mammals. Bus stop (talk) 13:40, 23 March 2012 (UTC)

And don't forget that many of your living creatures will support their own gut flora.--Shantavira|^{feed me} 14:19, 23 March 2012 (UTC)

(EC) Biomass, I knew there was a word for what I was thinking about but couldn't remember it! As for the more complicated aspects of the question, I was generally thinking about numbers, but diversity is an important aspect of the question too, and I guess the "right" answer to my question (which I'm sure isn't very easy to pin down :)) would be what area has the most organisms, but also the most diverse (assuming that multiple areas have similar numbers). I do need to ask, though, what about areas of the ocean, such as a coral reef? Or would there be less bacteria, etc. there than in the given example of a swamp or rainforest? 151.163.3.10 (talk) 14:22, 23 March 2012 (UTC)

That biomass article is pretty useful, I do have to say. I was able to find a great reference on it that has a great chart of biomass by ecosystem. I know biomass does not directly mean separate organisms, but it sort of indicates "amount of life in this area". 151.163.3.10 (talk) 14:26, 23 March 2012 (UTC)

Also note that since organisms take up a volume, not an area, the issue of the depth of organisms below, or above, the area also matters. I would expect that an area of water over the deepest part of the ocean might have the largest volume of organisms above and below it. (I wouldn't expect the density of organisms to be very high below the depth where light penetrates, but the water is some 7 miles deep, and even at a low density, that must still add up to a lot of organisms.) StuRat (talk) 19:25, 23 March 2012 (UTC)

I seem to recall reading (possible on these very pages), that 90% of the cells of a human body are "alien" bacteria. Assuming this to be correct, a living organism of some complexity could be host to the highest density of living creatures by volume. --Incognito.ergo.possum (talk) 22:54, 24 March 2012 (UTC)

Extinction of one magnitude

What is meant if light from a star has an extinction of one magnitude? Does this mean that the apparent magnitude is reduced to half of the absolute magnitude? --T.M.M. Dowd (talk) 19:17, 23 March 2012 (UTC)

Extinction happens along the way from the star to us due to absorption or scattering by intervening matter (like dust in the interstellar medium or the earth's atmosphere). An extinction of one magnitude means that the stars apparent brightness is fainter by one magnitude (factor 2.512) compared to what it would be in the absence of that matter. Extinction occurs in addition to the brightness reduction due to distance. --Wrongfilter (talk) 21:48, 23 March 2012 (UTC)

(Edit Conflict) No, extinction has nothing directly to do with the relation between apparent and absolute magnitudes.

First, remember that by definition 5 steps in magnitude are equal to a brightness difference of 100 times, so a one magnitude difference is equal to a brightness difference of 100^1/5 or (about) 2.512 times. This means that a doubling in brightness results in a magnitude decrease of about 0.8, and a halving in brightness results in a magnitude increase of about 0.4 (remembering that the greater the brightness, the lower the magnitude – the dimmest stars visible to the naked eye from the Earth's surface are "6th magnitude", the brightest are "1st magnitude", and the few very brightest have negative (apparent) magnitudes). Because of these relationships, it's important not to confuse halving or doubling (etc) the brightness with halving or doubling the magnitude.

The apparent magnitude of a star – the magnitude (assuming no obscuration by atmospheric or space conditions, etc) that you actually see, i.e. is apparent to you – can be much greater or much less than the absolute magnitude, i.e. the magnitude you would see if the star was at a standard distance of exactly 10 parsecs, depending only on the star's actual distance: for example, a star with an absolute magnitude of, say, 3.0 that is 10 parsecs away will also have an apparent magnitude of 3.0, while an identical star that is only half as distant, 5 parsecs away, will appear twice as bright, which would result in an apparent magnitude of about 2.2.

Extinction is a measure of how much a star is dimmed from what would be its apparent magnitude if nothing was obscuring it. Depending on the context, extinction can refer to either Interstellar extinction – the dimming effects of dust and gas in space between it and us – or to Atmospheric extinction which itself can mean either the dimming by absorbtion of our atmosphere in general, or the extra atmospheric dimming/absorbtion caused by the star being closer to the horizon than the zenith (since then we're looking at it through more atmosphere than if it were at the zenith). Typically, a star would suffer an atmospheric absorbtion or extinction of 1 magnitude at an altitude of about 10 degrees above the horizon compared to how it would look if it were at the zenith. At only 2 degrees altitude it would be dimmed by about 2.5 magnitudes; at 21 degrees by about 0.4 magnitudes: the actual amount is approximately the absorbtion at the zenith times the secant of the star's zenith angle (from Astronomy Data Book, J Hedley Robinson & James Muirde, David & Charles 1979).

In your particular example, an extinction of 1 magnitude (e.g. from 3.0 to 4.0) just means the apparent magnitude is 1 magnitude less that if there were no extinction – the absolute magnitude doesn't come into it. However, the brightness of the star will have decreased by 2.512 times.

All that said, there can be an indirect relation between interstellar absorbtion and the apparent and absolute magnitudes which are related by distance. The further a star is away, the greater amount of interstellar dust etc causing extinction there could be between us and it, causing greater extinction of the apparent magnitude. However, the interstellar distribution of dust is very uneven (though somewhat correlated with the plane of the Galaxy), so there is no simple formula. Two stars might lie in approximately the same direction from the Solar system and one be twice as distant as the other, but if the interstellar dust happens to be denser between them than between us and the nearer one, the further star will suffer more than twice as much interstellar absorbtion than the nearer, from our (the Solar system's) local point of view. {The poster formerly known as 87.81.230.195} 90.197.66.141 (talk) 23:03, 23 March 2012 (UTC)

Hey tpfka8821, you might want to double check the math in your statement, "This means that a doubling in brightness results in a magnitude decrease of about 0.8, and a halving in brightness results in a magnitude increase of about 0.4 ...". -- 203.82.87.14 (talk) 01:04, 24 March 2012 (UTC)

an editing opportunity

http://en.wikipedia.org/wiki/Lockheed_L-1249_Super_Constellation On this page, it appears the figures for empty weight and maximum takeoff weight may be reversed. I am not going to take the time to research further for a change to be made, but someone with an aviation interest may want to. That's it. Thanks. — Preceding unsigned comment added by 108.85.210.119 (talk) 19:22, 23 March 2012 (UTC)

Thanks. It certainly doesn't seem correct that the maximum takeoff weight would be less than the empty weight, but this doesn't necessarily mean the two values were swapped. One might just be wrong. StuRat (talk) 20:17, 23 March 2012 (UTC)

I just dropped a note on the user page of the editor who created this article with those figures last October . -- ToE 05:54, 25 March 2012 (UTC)

Eating behavior inheritance

I'm a bit puzzled about how an eating behaviour became a stable and consistently inheritable trait (particularly how predation or herbivory became stable traits). If the first predator/herbivore/etc consistently consumed meat or plants (mainly or exclusively), how it's possible to transmit that trait to the offsprings who would have no specific eating preferences? Is it because of some prolonged exposures to, say, meat and plants when animals were forced to feed exclusively on meat and plants? --188.147.71.38 (talk) 20:05, 23 March 2012 (UTC)

Digestive systems are heavily customized to match a given diet. For example, to eat grass, you need a digestive system with many compartments, like a cow's. Also, tools needed to obtain different food vary. Predators need claws and teeth suitable to kill their prey, for example. So, a species which inherits a preference for a food it can handle will survive and pass down those genes, one which does not will not. Also note that food preferences may be taught, rather than inherited. StuRat (talk) 20:11, 23 March 2012 (UTC)

The food preferences logically seem to depend on each individual organism. Not every cat, despite being carnivorous, eats solely meat and is capable to handle other stuff than meat. In evolutionary terms it's better to be omnivorous rather than have specific eating habits, so why some time ago a dietary separation took place?--188.147.26.232 (talk) 20:31, 23 March 2012 (UTC)

It's not always better to be omnivorous. Also note that the word is a bit of a misnomer, in that omnivores can not actually eat everything. Humans, for example, can't eat grass or carrion. To have a digestive system which could handle anything would mean maybe 90% of your body would be devoted to digestion. (Cows only eat grass, and look at what portion of their bodies are devoted to digestion.) The most efficient source of food is actually meat, so predators have an advantage there, provided they have a regular supply. For those animals which don't (like many humans), it's helpful to also be able to eat some other things. StuRat (talk) 21:47, 23 March 2012 (UTC)

Adding to the above, and this is something of a wild simplification, but the higher the level of intelligence, the more teaching probably has to be done to know what can be eaten. A frog doesn't know it eat flies — it has a reflex for shooting its tongue out at things that look like flies dancing in front of it, and it eats whatever it catches. It doesn't need to be taught anything. Evolution has given it just enough intelligence to get the job done. A dog, by comparison, knows instinctually how to kill (puppies all know, from birth, the "silent bite," that shake they do with their toys and later animals they catch), but doesn't know whether to eat what they have killed. They have to be shown that a particular dead animal is edible before they will generalize from this. (At least, this is what Temple Grandin claims. I suspect this is a different thing that dogs who try to eat rocks or cat poop.) So there's an interesting interaction of "instinct" (which is presumably genetic) and "learning" (which is not). Humans of course are quite flexible and need to be taught nearly everything — babies don't know anything much other than how to suckle, and that only gets you so far in life. --Mr.98 (talk) 22:16, 23 March 2012 (UTC)

See also Natural selection. If an individual, by genetic factors like mutation or a particular gene combination from parents, becomes better at finding/catching/eating/digesting food A than food B, then the individual is more likely to survive and pass its genes in an environment where it can get food A. Unneeded "advantages" like the ability to use foods with poor availability often come at a cost like needing more calories to keep multiple systems operational, having less resources for other things, being heavier and slower, being less specialized in teeth, digestive system and so on for more available food. Also note that "available" doesn't just mean what is in your enviroment but also whether you can get to it. Many predators need large muscles to catch and kill prey but the muscles require many calories and are heavy, giving poor endurance. The most famous human advantage, intelligence, also has costs. For example, our brains consume a lot of energy and child birth is very dangerous to both mother and child due to the size of the head. We can do a lot with our intelligence due to our hands and other factors. For many animals, larger brains with more intelligence wouldn't be worth the cost. PrimeHunter (talk) 22:35, 23 March 2012 (UTC)

I think the human difficulty in childbirth is more due to walking upright, which requires narrower hips. Women tend to have wider hips than men, to aid in childbirth, and often can't run as well as a result. StuRat (talk) 08:32, 25 March 2012 (UTC)

You seem to be wondering if acquired (perhaps taught) traits can be passed on genetically, an idea proposed formally as Lamarkism and generally discredited, though now rehabilitated to a limited extent by Epigenetics. The flaw in your logic is to assume there was only one "first predator" (or herbivore) from whom carnivory had to be passed on. This is illusory because an evolutionary "tree of descent" appears to have a single trunk, but ignores those branches and trunks, of what was really a bush, that died out.

Instead consider a breeding population of original animals, in which through imperfect genetic reproduction different individuals displayed various lesser or greater inheritable tendencies to carnivory. If the environment even slightly favoured carnivory, those "most carnivorous" would have better thrived, reproduced and passed on their tendency through the generations, while those "less carnivorous" would have tended to die earlier, reproduce less and therefore produce fewer "less carnivorous" descendent, until in time only the "more carnivorous" animals would be left, a paradigm of the mechanism of Natural selection. These in turn would be subject to further genetic variation, with Natural selection favouring ever greater carnivory, until an optimum fitness to the environment was attained. Similar considerations apply to most characteristics of most animals, except where they have attained an intellectual level supporting a culture (in the biological application of the term), which may then allow circumvention of environmental factors through non-genetic transmission of behaviours.

Just as individual animals in a population can have slightly different genetic traits due to imperfect reproduction and mutation, so they can exhibit slightly differing individual behaviours, degrees of intelligence or even personalities, but in the population as a whole, from generation to generation these tend to balance out or be neutral leaving the naturally selected genetic tenndencies to hold sway. {The poster formerly known as 87.81.230.195} 90.197.66.141 (talk) 23:31, 23 March 2012 (UTC)

Perhaps a more general discussion of "generalists" versus "specialist" animals which fill a specific niche would be helpful. While generalists (like humans) are able to survive in a number of environments, they don't always beat out specialists, as multiple specialists ideally suited to each environment may out-compete them in every environment. Bears, for example, are omnivores and "generalists", but this doesn't guarantee their survival. StuRat (talk) 01:40, 24 March 2012 (UTC)

90.197 did a good job on this, but I should just sort of repeat in case something was missed: this has the character of many questions (or even creationist arguments) about evolution, which work along the line of "how could evolution have managed to..." The answer is always the same - step by step. If evolution can't do something in bits and pieces it can't do it at all. But it has help from a lot of different mechanisms beyond strict Darwinian selection. To begin with, consider how evolution decides whether an animal should change diet (this is a just-so story, not a real model, but it is meant only to illustrate a path).

• When an animal is hungry, should it (a) starve or (b) try a non-usual food?
• If an animal eats the wrong food, should it (a) get infected/colic/whatever and die or (b) have some method of withstanding the unusual food ready?
• If the animal eats wrong food now and then and survives, should it (a) have some means to extract some nutrients out of it or (b) not bother with the expenditure of protein synthesis and DNA bandwidth?
• If an animal eats wrong food now and then and gets energy out of it, should it eat it a lot?

Now control over eating of non-usual foods must rest to some considerable extent in odorant receptors, which can pretty directly control what is revolting, but also in lots of other genes affecting perception. Culture also must play a huge role in what animals try.

Surviving and thriving on the food may have something to do with gut flora, which change in response to the diet and are transmitted to some extent between animals. Epigenetics also plays a role, I'm pretty sure. I just saw a really cool paper about prions being much more common and varied than we ever imagined, for that matter.

The plants themselves also get a say. Did humans domesticate opium poppies or did they domesticate humans? The same applies, less sinisterly, to many crops, not just those of humans but those of insects that pollinate and protect them, or any herbivore that scatters their seeds. I suspect even a prey species like deer show some kind of bizarre long-term selection to ensure that the weakest individuals don't outrun the wolf, so that the species as a whole is more fit, but I haven't seen it analyzed.

In practice, I think very few animals are really as fastidious as they're made out to be - they just have been the subjects of too few research studies. Caterpillars in the lab pretty easily abandon their usual "exclusive" hostplants. Farmers rear "cannibal cows", at least until the prions turn aggressive. Wolves turn out to eat a fair amount of berries and miscellaneous scats they run across. By and large, I think the first few questions of the Just-So Story have been answered for most forms of life long ago, and the issue seldom reopened. Wnt (talk) 23:51, 25 March 2012 (UTC)

If you restrict the discussion to what animals eat for energy, versus everything they consume, then they fall better into categories. Cats, for example, "eat" grass, but don't get any energy from it. Some birds also "eat" stones or clay, but don't get energy from that. StuRat (talk) 21:03, 27 March 2012 (UTC)