A bunch of questions about Biology/Ecology/Evolution and stuff.

So much sciency stuff! I am a marine biology/science major so I'll be able to answer a number of these. Just not this second cause I'm literally about to go to bed. I'll edit in answers tomorrow. However, I can answer some of my speciality off the top of my head real quick.

•I assume Fish are cold blooded, how does that work? They can't chill in the sun like a lizard can, where do they get heat? Do they even need heat? Water is much more stable in temperture, also as mentioned before warm water floats on top of cooler. Also deep sea fish have essentially anti-freeze in their system.

•In all the BBC specials, the fish just kinda hang out next to the sharks. This strikes me as incredibly stupid. Why don't they swim away? Are they just incredibly stupid? Sharks have specific times and areas they feed, other fish know this. Also many of those fish are actually cleaner fish, which eat parasites off all the others therefore no one eats them. It's a type of mutualism.

•How do sharks eat, anyway? It seems like it would be really hard to maneuver in the water, and fish can dart like nobody's business. How do sharks manage to coax a fish into their mouth? They hunt. Sharks are incredibly fast when they want to be; their streamlined bodies are built for speed. Edit: Forgot to mention that their shading (dark on top, light on bottom) is a type of camouflage that allows them to ambush their prey.

•There's a lot of crazy shit going down at the bottom of the ocean, when I get that far with my world building can I pretty much just make crap up, and have it make as much sense as half the things down there? We have very little idea of what's actually going on down there. I suggest you look up whale and wood falls, hydrothermal vents, and cold seeps to get an idea of the life down at the very bottom.

•Do fish need oxygen? If no, why not? If yes, how do they get it? Their gills take in water, getting the dissolved O2 from it. (yes oxygen is dissolved in water)

•How improbable is it to have giant sea monsters? This runs into the same problem as the previous 'big herbivores' thing, why are all the big whales and stuff so gentle? Is there any reason there isn't something much... nastier? Animals can grow much larger in water because buoyancy counteracts the effects of gravity. And whales are "gentle" because they are herbivores; herbivores are larger because they can get more net energy from the prim producers than carnivores can from herbs (among other reasons). Also giant squids exist; they are nasty.

•How do fish live with the immense pressure bearing down on them forever? I mean, just going a thousand feet down has to put incredible strain on a body, and there is life on the ocean floor, several miles down! They don't invest energy into making strong skeletonal structures like us land animals do. They're much more...jelly like, flexible.

Edit: edited for clairty. Thanks. That is what happens when I try to sound smart while tired.

edited 6th Sep '11 1:26:04 PM by MurkyMuse

"Buoyancy."

Animals:

• Is there a common number of unique species among each trophic level? i.e. you have ten different kinds of plants, supporting five kinds of primary consumers, supporting three secondary, etc., or is it random?

It depends on various factors, including the age of the ecosystem (older has more), the level of disturbance (intermediate has most), how isolated the ecosystem is from other similar ecosystems (less isolated has more), and other things.

• I hear that about 10% of energy is passed up through trophic levels, after a consumer consumes something. Does this translate to each trophic level having 10% of the biomass as the last?

Not always. Normally it's roughly like that, but in some the herbivores (for example) eat the plants (for example) so quickly that there is more biomass in herbivores than in the plants.

• What makes animal blood red? I know that insects have different colors, and I'm not sure about fish. Why is it that way?

I know it depends on whether they use haemoglobin or another compound to store oxygen. I don't know why different animals use different compounds.

Plants:

• Can plants get sick, meaning do bacteria or viruses ever infect them? If no, why? If yes, what are some typical effects on the plant?

Typical symptoms of viruses include discoloured areas on the leaves ad/or flowers and stunted growth (other things can cause that too). I think some bacteria can infect plants, but I don't know how.

• Why is green the color of most plants? Is there any specific reason for it, or is it just because? If there is a specific reason, how do plants like red lettuce or wheat (I can't think of any other differently colored plants) survive?

The sorts of chlorophyl which gets the most energy from unfiltered sunlight are green. I don't know the answer to the other part of that question. Other sorts of chlorophyl get more energy from light after it's been through enough water, 'though, hence the variety of algal colours.

• In line with the animal domestication questions above, why were the plants that were domesticated originally sought after? Specific plants I want to know about are: Wheat, Rice, Alfalfa, Cotton, Corn, and Spices in general. Were those immediately recognizable as food by native man? What traits of them led man to breed them? How much did genetic engineering by man change them, i.e. could I recognize them 30, 000 years ago?

The best plants for domestication put a lot of resources into a particular tissue at some point- for example the wild ancestors of domestic cereals put a lot of their resources into their seeds at once. Wild wheat was smaller, and had fragile seed heads and fibres on it's seeds to catch the wind. I would guess wild rice and corn were similar. They probably wouldn't be recognisable, except to someone familiar with very old breeds of those plants.

Insects:

• Why are insects always so small? I've heard that they were much bigger in the time of the dinosaurs, what changed?

The concentration of oxygen in the atmosphere. Insects don't have a very efficient respiratory system.

• Do other insects aside from butterflies have 'staged' lifespans, meaning multiple unrecognizably different creatures, that are all just different times of life for one individual?

Yes. Most, 'though not all, insects have that. Flies develop from maggots, mosquitoes from aquatic wrigglers, beetles from grubs, ants and bees from larvae which stay in the hill or hive. Many wasps have larvae which live inside and off another insect.

• Why are so many (especially tropical) insects brightly colored, when it would make more sense for them to be green, to blend in with their surroundings?

In some, it's so predators of other, less poisonous insects know not to eat them. I think it might also sometimes have to do with finding mates.

• On predators, do they more often trap their prey (like web-making spiders) or hunt their prey (like non web-making spiders)?

Wasps, carnivorous flies, and dragonflies hunt. Mantids stand in wait and antlions trap. Those are all the carnivorous insects I can think of at the moment, 'though I'm sure there are more. I don't know which is more common.

• Do they usually use poison to stop their prey from fleeing, or just to kill them faster? When they kill something, do they take it back to their lair, eat it right then and there, or does it vary by species?

I'm pretty sure wasps use venom to stop their prey from fleeing. I don't know how other venomous hunting insects use it.

• On prey, do they ever have effective means of self-defense? Shooting poison out of their eyes or something?

Anything with a sting will sting in self-defence, and a lot of insects without stings are poisonous. A lot of other insects are camouflaged, or imitate something more dangerous than they are.

• Why are ants so damned civilized? What makes them special, so they can have rudimentary societies, and not other insects? How much control does the Queen actually have over individuals?

Part of it is that all the bees or ants in a colony are siblings (and males are clones of the queen), so kin selection means they have an interest in helping each other, and that an unusual mechanism of gender determination allows for a lot of control over gender ratios. The queen produces a hormone which keeps other females sterile, I don't know how much if anything she controls beyond that.

• What is the evolutionary reason for having small insects with enough poison to kill an adult human (Brown Recluse spider)? It doesn't seem like they'd ever need it, why would they have it?

I guess it's for defence against a vertebrate. I guess against something much more resistant to that poison than we are, since insectivores tend to be pretty small.

• EDIT QUESTION: How do insects like the Mosquito, which have a proboscis, oxygenate? Do other insects just have mouths/nostrils and lungs like we do?

No. I forget exactly how their respiratory system works but it's quite different from ours.

Reptiles:

• What is the advantage for being cold-blooded?

Needing less carbohydrates.

• What do most reptiles actually eat? I have never in my life seen a reptile doing anything other than sitting his ass down on a rock. Is that also just because I don't know anything about reptiles?

I think most of them eat invertebrates of one sort or another.

Amphibians:

• I know that amphibians always start their lives in the water. Is that always fresh water, or can they be hatched in salt water as well? If they can only live in fresh water, why can't they live in salt?

They all need fresh water, because in salt water they're dried out by osmosis. In fresh water osmosis pushes water into them, but they deal with that by excreting water.

• But beyond that, if you know anything cool/special about amphibians, lay it on me.

Frogs need very high quality water. One of the first signs of declining water quality can be frogs dying.

Birds:

• Again, we hit the problem of size. There are certainly some big birds out there, California condor has a wingspan somewhere around 6 ft, but the vast majority are the size of a mouse. Why is that?

The bigger you are, the harder it is to fly.

• Is there any particular fashion the feathers are arranged in, or is it more the fact that there are feathers that helps them glide, rather than the placement?

I think their arrangement is relevant somehow.

• On the breast/head of a bird, what is that stuff? It's not feather, it's not fur (or is it?), what's going on there?

I'm pretty sure it's not fur, but I don't know what it is.

• What advantage does a nest give, and what are ideal qualities of nests?

One feature of the ideal nest is that it's somewhere hard for non-flying animals to get to, to keep predators away. Another is being hard to see.

• What's the difference between an owl and any other bird, how are they evolved differently?

Owls have big ears so they can hear better than most birds, and big eyes adapted for seeing very well in low light. They're relatives of falcons that have evolved for hunting at night.

• In all the BBC specials, the fish just kinda hang out next to the sharks. This strikes me as incredibly stupid. Why don't they swim away? Are they just incredibly stupid?

Were these the same sorts of fish as those shark ate?

• Do fish need oxygen? If no, why not? If yes, how do they get it?

They do. Water normally has a small amount of oxygen dissolved in it, enough that fish can live off that.

• Is there a common number of unique species among each trophic level? i.e. you have ten different kinds of plants, supporting five kinds of primary consumers, supporting three secondary, etc., or is it random?
  • There will usually be one "apex predator," but beyond that, no.
• When predators hunt in packs, how good are their tactics, usually?
  • It varies with the species. Wolves only have about a 10% success rate, while African wild dogs (Lycaon pictus) have around 90%.
• Is there any reason that animals don't have chlorophyll, besides that they don't? It seems like a much more efficient means of attaining energy than grazing.
  • There are a few animals that have mutualistic relationships with photosynthetic algae, but for the most part, animals have much higher energy demands than plants, which means that photosynthesis simply wouldn't work (on an overcast day, the animals effectively wouldn't eat that day).
• What makes animal blood red? I know that insects have different colors, and I'm not sure about fish. Why is it that way?
  • This one has been covered pretty extensively, but I'll mention it anyway. Oxygen binds to hemoglobin in our blood, which carries it to our body cells. It's red because hemoglobin is iron-based. This is true for all Craniates. The insect method of respiration is very inefficient, which is also why they can't grow as large as they did during the Carboniferous period.

• Can plants get sick, meaning do bacteria or viruses ever infect them? If no, why? If yes, what are some typical effects on the plant?
  • There are plant viruses, but I don't know much about them. Most plant diseases (at least the high profile ones) are either caused by fungi (Dutch Elm Disease, Chestnut Blight, the Irish Potato Famine) or insect larvae (Emerald ash borer, Asian longhorn beetle)
• In line with the animal domestication questions above, why were the plants that were domesticated originally sought after? Specific plants I want to know about are: Wheat, Rice, Alfalfa, Cotton, Corn, and Spices in general. Were those immediately recognizable as food by native man? What traits of them led man to breed them? How much did genetic engineering by man change them, i.e. could I recognize them 30, 000 years ago?
  • Early humans had to learn pretty quickly which plants were edible and which ones weren't. With the advent of agriculture, it was a simple matter of transplanting those edible plants to a controlled area, then applying the same selective breeding techniques that we did to domestic animals, selecting for the plants that produced the biggest yield. As one might expect, this has caused quite a bit of variation from the plants' wild ancestors (for example, wild watermelons are less than half the size of the ones usually sold as food, while wild bananas are almost unrecognizable).
• Why are insects always so small? I've heard that they were much bigger in the time of the dinosaurs, what changed?
  • See the above comments about hemoglobin.
• What percentage of insects have the capacity to fly? Does this vary by region?
  • Insects being able to fly in their adult stage is the norm. There are exceptions, of course.
• Do other insects aside from butterflies have 'staged' lifespans, meaning multiple unrecognizably different creatures, that are all just different times of life for one individual?
  • Other people have already mentioned the numerous insects with complete metamorphosis (flies, butterflies, wasps, beetles), but many undergo what's called incomplete metamorphosis, in which the insects hatch from their eggs into what's called a nymph, which looks like a smaller, wingless version of the adult. Many nymphs (dragonflies, stoneflies, mayflies, etc.) are also aquatic.
• Do they usually use poison to stop their prey from fleeing, or just to kill them faster?
  • The only reason to kill the prey faster is so it can't get away. There are certain wasps that lay their eggs on the bodies of other arthropods, such as spiders or cockroaches, and they need the host to be alive but immobile to do so.
• When they kill something, do they take it back to their lair, eat it right then and there, or does it vary by species?
  • Most insects that actively hunt don't have lairs. The only ones that do are ants and wasps.
• On prey, do they ever have effective means of self-defense? Shooting poison out of their eyes or something?
  • Most insect prey prefers to simply escape. The bombardier beetle sprays two chemicals out of its backside that, when mixed, produce a very volatile reaction that can burn a predator's face and stain human skin.
• How do insects like the Mosquito, which have a proboscis, oxygenate? Do other insects just have mouths/nostrils and lungs like we do?
  • No. Insects take in oxygen through holes in their sides, which then diffuses directly into their body cells. This is why they don't have hemoglobin. Arachnids (e.g. spiders and scorpions) breathe through organs known as book lungs, the openings of which are found on the underside of their abdomens.
• What's with the tongue thing?
  • I assume you're referring to the act of flickering their tongue in and out of their mouths that snakes and monitor lizards do. The tongue picks up airborne particles. The snake then inserts the two forks of its tongue into an organ on the roof of its mouth called the Jacobson's organ. Basically, it's how they smell. (On a semi-related note, this organ is a highly developed version of the vomeronasal organ present in many mammals. If you ever see a male horse part his lips and expose his teeth, he is attempting to use this organ to pick up the scent of a mare in heat.)
• Same question as with insects, why are most reptiles so small? Aside from the komodo dragon and some snakes, I can't think of any that are bigger than my arm. Do I just not know anything about reptiles?
  • As has been mentioned, most crocodilians are quite large, with even the smallest (the African dwarf crocodile) being around 5 feet (1.5 meters). There are also a number of large turtles, including sea turtles and the Galapagos and Aldabra giant tortoises. There are also several monitor lizards larger than a human arm (as an example, the Australian perentie is about 8 feet long, and it's only the fourth largest species). Also, some of the prehistoric reptiles were truly gigantic (Tylosaurus proriger, a marine reptile related to modern monitor lizards, was around 50 feet long).
• What do most reptiles actually eat? I have never in my life seen a reptile doing anything other than sitting his ass down on a rock. Is that also just because I don't know anything about reptiles?
  • All sorts of things. Most of the small lizards are insectivores. Crocodilians, snakes and monitor lizards are pretty much obligate carnivores. Iguanas are vegetarians. The Galapagos marine iguana only eats a specific kind of marine algae. Land turtles will generally eat whatever they can find, while sea turtles eat mostly jellyfish.
• Why haven't any reptiles ever been domesticated? What traits do they not have that other animals (which were domesticated) have?
  • Most domesticated mammals and birds are naturally social, whereas reptiles are usually solitary, even fiercely territorial. Also, mammals and birds are generally more intelligent than reptiles, and the few reptiles that can be called intelligent are also the ones most likely to see humans as potential prey.

• I know that amphibians always start their lives in the water. Is that always fresh water, or can they be hatched in salt water as well? If they can only live in fresh water, why can't they live in salt?
  • Amphibian skin is incredibly permeable. If they lived in salt water, the salt would suck all the moisture out of their bodies, and they would die very quickly.

• Is there any particular fashion the feathers are arranged in, or is it more the fact that there are feathers that helps them glide, rather than the placement?
  • For the flighted birds, the largest feathers tend to be on the wings and the tail. The wing feathers are stiff, allowing the bird to get lift (without feathers, their wings are scrawny and pretty much useless). Tail feathers serve as rudders. In several species, males will also use their tail feathers to attract females.
• Birds can see a lot farther than any of us can. How does that work? If they're looking at a mouse running along the plain a hundred yards away, does it appear bigger to them, or just more detailed?
• What advantage does a nest give, and what are ideal qualities of nests?
  • Aside from what has already been said about safety, the nest also keeps the eggs together in one place. This is pretty much the only ideal quality, since the shape, makeup, and amount of care put into the nest varies greatly from species to species. Canada geese simply stand in one spot, grab whatever they can reach without moving, and make that their nest. Swiftlets make shallow cups on cave walls out of their own saliva. Hummingbird nests are made out of spider webs and moss, and are so small that even the baby hummingbirds are crowded.
• What's the difference between an owl and any other bird, how are they evolved differently?
  • Owls are as much birds as any other. Their clade just happened to hit on a body plan that worked and was fairly unique, so it stuck. Despite what some people think, owls actually have fairly average night vision. However, they do have a superb sense of hearing. Their flat faces serve as collecting dishes to direct the sound to their ears. Their ears are also asymmetrical, with one being noticeably higher than the other, allowing them to pinpoint the origin of the sound, in some cases even through several inches of snow.
• Again, domestication. But not to as great an extent this time, birds aren't really domesticated, besides Chickens. What's the deal with domestic Chickens?
  • One thing not touched upon was the fact that chickens breed quickly.
• I assume Fish are cold blooded, how does that work? They can't chill in the sun like a lizard can, where do they get heat? Do they even need heat?
  • The whole cold blooded/warm blooded thing is not really accurate. I can't quite recall what is off the top of my head.
• In all the BBC specials, the fish just kinda hang out next to the sharks. This strikes me as incredibly stupid. Why don't they swim away? Are they just incredibly stupid?
  • One, a large shark will create a slipstream. The fish can swim in that using far less energy than they otherwise would. Two, sharks, particularly ones that hunt large prey, are fairly messy eaters, which creates a fair bit of leftovers that smaller fish are quite willing to capitalize on. Three, sharks generally aren't very good at turning quickly, so the safest place to be is often directly behind its pectoral fin.
• How do sharks eat, anyway? It seems like it would be really hard to maneuver in the water, and fish can dart like nobody's business. How do sharks manage to coax a fish into their mouth?
  • Whale, basking, and megamouth sharks are filter feeders. Angel sharks lie in wait on the sea floor, then open their mouths quickly, creating a vacuum effect. Great whites ambush their prey from below. Mako sharks can swim up to 30 mph (50 kph), so chasing down prey isn't much of an issue for them.
• There's a lot of crazy shit going down at the bottom of the ocean, when I get that far with my world building can I pretty much just make crap up, and have it make as much sense as half the things down there?
  • Well, even as crazy as it all seems, the deep sea things do still follow the same basic biological rules as their not-so-deep relatives, just in different ways due to the different resources available (for instance, organisms that live in volcanic vents usually have a mutualistic relationship with chemosynthetic bacteria, which enables them to metabolize sulfur).
• How improbable is it to have giant sea monsters? This runs into the same problem as the previous 'big herbivores' thing, why are all the big whales and stuff so gentle? Is there any reason there isn't something much... nastier?
  • Whales, I feel I should mention, are not herbivores. They are, in fact, predators. Most people tend not to think of them as such, since the animals they eat are so much smaller than they are, but yes, even the baleen whales eat small fish and crustaceans. (Look up the hunting strategy of humpback whales some time. It's quite fascinating.) Numerous people have mentioned prehistoric sea creatures that have grown quite large, particularly Carcharodon megalodon. I also refer you to my earlier mention of Tylosaurus (in fact, the entire Mosasaur clade would qualify for this), as well as the Pliosaurs, particularly Kronosaurus and Liopleurodon.

edited 3rd Oct '11 8:23:56 AM by apocalemur

Planet Earth had a brief segmenton these dogs. This youtube link has the clip, but it's replaced the (very helpful) commentary with music. Episode 1

Most land-based packs tend to use their numbers to drive prey towards hidden flankers. The surprise of the attack helps panic prey and makes it easier for flankers to get them. Mass is a big factor in bringing down larger prey. What kills larger prey is typically blood loss, suffocation, and exhaustion which require you have several pack members attacking it since it out-masses you. Packs of lions are capable of bringing down water buffalos, but a single lion trying to take one on is likely to get itself killed.

Most land-bound packs tend to use the same tactics as you can see. What sets them apart is:

1. Choice of prey (some prey is less alert, has calves with them for long periods of time, ratio of prey mass to predator mass is also, obviously, very important)

2. How well pack leaders can organize their subordinates (having each member attack at the right time is key)

3. How well they use the terrain (in the video of the african dogs, they manage to force one of the impala into a lake which would have led to an easy kill)

4. How well the pack as a whole adapts to the changes during the attack (no battle plan survives contact with the enemy)

5. Past Performance. The more kills a pack has, the more well-fed it is, the easier it is to make more kills since each animal will have a higher level of endurance.

6. Location. Packs in equatorial regions have it easiest. The only changing conditions they have to consider are rainy seasons and herd migrations. Temperate and polar regions have to contend with migration and fewer prey in winter leading to significant fluctuations in pack size.

7. Pack Size. Smaller packs have difficulty making kills but have less mouths to feed. I know that wolves at least will tend to split into separate packs if a single pack gets too large (I can't say what number on average though). I kind of wonder if there isn't some biologist out there who has compiled statistics regarding successful kills based on pack size. Would be a cool thesis.

If you want an example of some avian pack animals, look into Harris's Hawks.

edited 7th Oct '11 12:33:09 AM by Urzed

I think this thread has been abandoned by the OP. That is, he said he'd ask some more questions 'tomorrow', but he hasn't.

So... is there any point in continuing to answer them?

Oh, I've been following this. I totally forgot about those other questions though... Woops.

But I think we could pretty safely call this thread 'done' now.

One question about genetics: If you're infused with DNA from say, a man whose reproductive system got fried because he was at a nuclear weapons tests, will the former who received the latter's DNA get his reproductive system fried?

Uh...it's kinda hard to answer that one. For starters, you need to define what "infused with DNA" means in this context and what mechanisms it'd use. Remember, there's a reason why Magic Genetics is a subtrope of Artistic License – Biology.

In order for something to replace you DNA with the DNA from another individual, the DNA molecules in the nuclei of nearly every cell in your body would have to be removed. A more plausible scenario is having the DNA in your body modified by some outside influence, like a specially engineered virus. That's still science fiction, but at least it makes sense on some level.

Epic necro, by the way.

edited 27th Aug '14 11:43:45 AM by Demarquis

What about if it's to grant Person A Person B's skills (physical strength, increased IQ, etc.)?

That'd be LEGO Genetics. At that point you can basically say A Wizard Did It. Don't bother with a "scientific" explanation, you won't find one that works unless you assume some kind of superscience beyond what we can even imagine at this point.

So basically, the Next-Generation Special Forces from Metal Gear Solid are LEGO Genetics?

Another question, can clones reproduce?

Yes. Clones are just identical twins that were fertilized artificially.

theoretically, yes. Clones should have all the functionality of the original. However, in practice there's a fair degree of protein and genetic damage which causes premature aging. This degradation would also hinder sperm and egg formation. A well made clone might escape these issues and an individual might just get lucky but with current gen tech clones are not fertile.

edited 28th Aug '14 8:58:25 AM by Belisaurius

I was speaking theoretically, not pragmatically. Our technology is too limited to do what I just suggested reliably. In the future this may change.

Yes. Very much so.

and Thanks

Thank you too.

Another thing about cloning: Can DNA from a dead person still be useful for cloning?

Again, in theory, yes, if the corpse is freshly dead. But again, we dont actually have the technology to take advantage of it.

It doesn't really have freshly dead. The DNA just has to be intact enough that the pieces can be spliced together.

Theoreticaly one could clone a human from a single tooth or strand of hair.

We've managed to pull DNA from bone samples that are thousands of years old. Some mummies have given us enough genetic information to perform paternity test.

Don't try to pull DNA from human hair, though. Unlike most mammals, human hair doesn't contain DNA for some reason.

Where have you heard that?

Human hair does contain DNA, but only in the papilla. There is no dna in 'cut' hair, you need the root.

edited 28th Aug '14 1:34:29 PM by m8e

Somewhere in middle school, I think. However, I do concede that the root does contain some DNA. My only point is that you can't make a clone out of hair clippings.

In regards to certain parts of the body, can peeled off nails contain DNA?

Another question: What happens if a woman has sex with a man who was too irradiated that he cannot reproduce?

They have fun with no worries.