Ecogeographical Rules

Text transcription of audio lecture on ecogeographical rules (80% accuracy)

Ecogeographic Rules

Ecosystems by geography. Couple more minutes. So eco geographical rules. You may think that these sound very much like biology questions, but this is the intersection between biology and geography. We're talking about the distribution of organisms and how they distribute themselves. And so that is a geographic issue and question. But again, because we're talking about the way in which organisms live, we are talking about the distribution of ecosystems. So it's eco geography or biogeography in other cases. But there are a number of rules in eco geography, and these are just some of them. And I've always thought that eco geographical rules are actually really cool, which is why I did the question on this. So the first one, true or false island dwelling organisms will over time evolve into smaller organisms. Why did you answer what you answered? Anyone who was willing to give the rationale unless you know what the eco geographical rule is.

Foster's Rule

Okay, so you're on to it if the island is small. What else is going to be small? Food resources? Yes. So this is Foster's rule, which says that over time, organisms on an island will evolve basically according to how much resources they have available to them food, water, reproduction, etc.. And what we notice is that over time they actually become smaller because their resources are constrained. So it is true that island dwelling organisms will evolve into smaller organisms over time. And this is Foster's rule. The next one was organisms inhabiting cooler climates have thicker and larger appendages than their warmer climate dwelling counterparts. Does anyone want to talk about why they answered, what they answered?

Allen's Rule

Yeah. So this is actually called Allen's rule. And what it states is that the body shapes and proportions of endothermic vary by climatic temperature, by either minimizing exposed surface area to minimize heat loss in cold climates or maximizing exposed surface area to maximize heat loss in hot climates. So organisms inhabiting cooler climates will have thicker and larger appendages than their warmer climate dwelling counterparts. 

So let's look there's a good example here with here's. Okay. In Alan's life, it's a new thing that Google is doing that really upsets me. What? It's it. It's like auto completing, But then when you select it, it won't actually do it. And so what we see is that they're specifically talking about the ears of these types of rabbits. So ears of whatever type of rabbit this lepus americanus that inhabits the subarctic regions has smaller ears than those that we would find in the desert here. The Levis, California case and we noticed this with a number of other species as well. We have like Arctic foxes as well. So we want to minimize the surface area that's exposed to heat loss. Whereas when we are in a warmer climate, we want more surface area to allow for heat to be whisked away from us. So Alan's rule, I believe there's one rule that gets more specific. So it's Bergman's rule actually to see if Bergman's mentioned. Here is we have Bergman's rule, which talks about somewhat of the same thing where you have. And now I'm getting confused because it seems like is the inverse now where you get smaller penguins, the closer you get to the equator. I need to rework this one. Don't memorize that one. I need to figure out why it's Alan's rule, and Bergman's rule seem to say different things. Shallow water. Marine life is larger than its deep sea counterparts. 

Gallagher's Rule

It has to do with the sun. So darker skin, for example, with with people because they're exposed to more ultraviolet radiation and insulation from the sun. They do not need to convert as much sunlight or radiation to vitamin D, and darker pigmentation is less efficient at doing that. The whiter your skin is, the more conversion that happens. So people that live at the poles are going to have lighter skin and they need that so that the skin, the melanin will be converted and produce the precursor to vitamin D3. So that is Gallagher's rule. That is why you I mean, you'll see it's people that are native to the equator. Equatorial region have darker pigmentation than those at higher latitudes.

Harrison's Rule

And then the final one parasites get smaller, the larger their host becomes. Two people said True. Why would you say true? I'm just curious. Don't want to admit it. Okay. The answer is false. A parasite lives off of a host, and so the larger the host gets, the larger the parasite itself will become. This has been observed in ticks that when ticks feed on larger organisms, they tend to also get much larger. So if they get on like, I don't know, a horse versus a dog, they will be much larger because they're feeding off of the host. So that that tends to make sense. And that is Harrison's rule that states that parasite body sizes covariate with those of their hosts. And it was actually lice, not ticks. It works equally well, he says, for many other groups of parasites, including barnacles, nematodes, fleas, flies, mites and ticks. So, yeah, they will get bigger, the bigger their host gets. I'll figure out this Bergman's rule issue, the surface area, because this confuses me.