GURPS: Ecosystems and Evolution

[Vaevictis Asmadi]

Originally Posted by MagiMaster

Another question I need to write down: If you have four animals, A consumes its body weight per day, B is just like A but has trait X and consumes 3/4 its body weight, C is just like A but has the (non-conflicting) trait Y and also consumes 3/4, and D has traits X and Y. How much should D consume?

The easy answer would be (3/4)^2, but it's probably also wrong. Trait X and trait Y are presumably biological traits, and how they interact with each other in the body of animal D depends entirely on the animal's physiology and what exactly the two traits do to the animal's metabolism, and to its other bodily functions that ultimately impact its energy budget. I think the question is just too complex to answer, except by conducting in-depth studies of real animals.

[MagiMaster]

While I agree that this is a gross oversimplification of real metabolisms, I'm just wondering which of the two options (or what other options) produce the least bad results. Bad results in this case don't mean just unrealistic, but ungameable too. Currently, neither seems to win out on either simplicity or obviousness, and I don't know what else to go on. I can't study this on real animals without another degree and some significant grant money.

[Vaevictis Asmadi]

Of course, I know you probably can't study it that way. I wasn't suggesting you should. I was just saying, that's what it would take to find a realistic answer.

For an answer that seems plausible and simple enough to use in a game, I think multiplicative makes more sense. But if X and Y are Advantages, I don't know whether multiplication or addition would be more fair and balanced.

[MagiMaster]

The Xs and Ys from Space are a combination of advantages, disadvantages and 0-point features.

The equation was 1.25 * factor * mass^(-1/4) for fraction of body weight eaten per day. So if factor can be broken down into (factor1 * factor2 * ...), each factor needs to be between 1 and some number depending on how many factors there are (and their relative importance). For the moment, imagine there are four factors that coud be either 1 (most active), 0.6 or 0.3 (least active) each. Are there any combinations of mass and factors that gives really weird answers?

[MagiMaster]

I'm working on the factors some and I was wondering whether anyone else thinks that the IQ of the species has anything to do with how much they need to eat. I can seem a number of arguments in both directions (from more efficient hunting to more energy spent on brainpower), so maybe it just balances out. Either way, it would be a small effect and may not worth bothering with.

Also, how would special abilities, such as projectiles or invisibility change things? Would those also tend to balance out?

[lwcamp]

Originally Posted by MagiMaster

I'm working on the factors some and I was wondering whether anyone else thinks that the IQ of the species has anything to do with how much they need to eat. I can seem a number of arguments in both directions (from more efficient hunting to more energy spent on brainpower), so maybe it just balances out. Either way, it would be a small effect and may not worth bothering with.

I've heard convincing arguments that brain power is correlated with calorie budget. Basically, brains are energy intensive organs that cost fuel whether they are used or not. Creatures with a large energy budget can afford to spend some of that on a big brain with lots of processing power. As the metabolism gets lower, the same brain costs a correspondingly larger amount, and is a correspondingly larger drain on the animal's available resources. This is borne out by trends seen in animals. Mammals and birds tend to be smarter than reptiles. The smartest reptiles - monitors and crocodillians - also have the highest aerobic metabolism among reptiles. Reptiles in general tend to have more complex behaviors and learn faster than amphibians (which have a corespondingly lower metabolism), and snakes (which have a low metabolism) seem fairly stupid compared to more active lizards. Many of the warm blooded "fish" (such as the lamnid sharks) are noted as having sophisticated behavior that would correlate with higher intelligence than expected for typical fish.

Luke

[MagiMaster]

Thanks for the info. So far I've got the following categories of factors (sorted by my guess at relative importance):
- Trophic level (Aliens II)
- Locomotion (Aliens III)
- Temperature control (Aliens VI)
- Intelligence (Aliens IX)
- Skin (Aliens VI)
- Strategy (Aliens VII)
- Gestation (Aliens VII)
- Organization (Aliens IX)
- Mating (Aliens IX)

I think the first three are the biggest factors, the next three are medium ones, and the last three are fairly small.

Some of these lists are kind of long and complicated, so I don't have numbers to attach to them yet. I might can generalize Skin by the DR and TT it grants, but I'm not sure anything else generallizes easily. (IQ could be used, but it's a small enough range either way.)

Edit: Oh yeah. I'm also not sure if autotrophs fit into this scheme or not, but I guess I'll have to wait until it's more complete and see.

[Vaevictis Asmadi]

lwcamp is right about the brain being a hungry organ. The theory about human evolution is that our ancestors couldn't have larger brains until they started eating significant amounts of meat. Meat has denser energy than plants and is also easier to digest, allowing us to have smaller guts and shorter intestines.

Well pure autotrophs shouldn't consume anything, right? Even an Earthly carnivorous plant will only consume what it needs for minerals it can't get in the soil. So it should only matter for mixed autotroph/heterotroph creatures like lichen, and then I think a big factor is what % of their carbon is primary production and what % is consumed.

[MagiMaster]

For this system, I have a given biomass equivalence of the primary energy source, and I'm using consumption to estimate the population, so I think I'll have to come up with some kind of figure for autotrophs, but it may not us the same formula. I think I remember reading that the power of mass for plants is different.

[Anthony]

Originally Posted by MagiMaster

If it's in equilibrium, then the heat generated and the heat radiated should be the same

Talking about a larger equilibrium -- the system containing the heat difference and the life form is presumably persistent, which will only happen if there's a heat source and a heat sink and the two are in balance.