If a freak giraffe, if a mutation causes giraffe to have a slightly larger neck, then because it's avoiding the competition with cords now, the giraffe's neck over generations can even get taller and taller until you get a giraffe. Where this, you see the opposing interests of the consumer and resource, can lead to an evolutionary arms race. So, notice that as the giraffe is getting taller, the tree is getting taller, right? So the giraffe is feeding on a short bush, right? The tree is a little taller, now the giraffe can't reach.
So this is looking at a predator-prey interaction instead of a competitive interaction. Yes. I have no idea. But it's in there somewhere towards the end.
Thank you. Thank you. So basically, so we're asking on the little short foot, broken to a taller tree, giraffe can't reach anymore. But then a mutated giraffe has a longer neck and now can still reach the tree. Now, any tree, any mutation in the tree that makes the tree even taller, the giraffe can't reach it.
But then you get another mutation in the giraffe for a longer neck, now it can reach the tree again. Do you see how they're kind of evolving, sort of in response to the change in the other one? This is what we call an evolutionary arms race.
Right? Just like you get more weapons, so I get more weapons, so you get more weapons, so I get more weapons, so you get more weapons, so I get more weapons. And now we have, everybody has enough nuclear weapons to blow up the world like 18 times.
So we talked before about, you know, some of the strategies that the resource species, the prey or the plant, uses to avoid predation. Like being fast, being too big, not watching an elephant, having weapons like the horns on an antelope. I mean camouflage, can you see what's in that second picture now? Can you see it?
It's a chameleon that looks exactly like the leaf. They can mimic poisonous things. So we've got the false coral snake.
You guys heard the saying, red on yellow, kill a fellow, or red on black, friend Jack? Don't believe it. That's only true in the US.
If you go to Costa Rica, or Nicaragua, or South America, there's different colored porosnays that are just as poisonous. Learn that quick. I'm just traveling. But, so you see, one of them is pointed at the other one's not, but the bright colors make the potential predator think that it might be dangerous. And, of course, you have to take armor down.
In all of these cases, how might the predator adapt to deal with it? I'm sorry? Okay, so the predator is going to adapt to get faster.
To get better at recognizing that community among the leaves. To get better at telling the difference between the two species. And so this is our...
Evolutionary arms race. The antelope gets faster, the cheetah gets faster. The antelope gets even faster, the cheetah gets even faster.
We've got raptors, eagles, things with those beaks that will puncture right through an armor. Means of detoxifying poisons. So some animals produce an enzyme that can neutralize the poison of a prey.
Everybody heard of the book Alice in Wonderland? Anybody read the book Alice in Wonderland? So you remember the Red Queen?
Alright, so what you sometimes hear is the Red Queen hypothesis. The Red Queen told Alice that it takes all the running you can do to keep in the same place. So this is the idea of this, they're adapting and they keep adapting, but they have to keep adapting to keep up with the changes in other species.
Okay, so the red queen told Alice you gotta keep running just to stay in the same place. So the giraffe had to keep getting a longer and longer net just to keep eating the same things. Right? The prey species might have to keep getting faster and faster just to keep getting away from the same lion who's getting faster and faster.
So it's the same idea as the evolutionary arms race. Not a lot of people use right-wing hypothesis anymore because the Borgals were more related to the New York Times. So, we tend to talk about this in terms of animals, but plants have a lot of defenses as well.
And so plants produce what we call secondary compounds. So, compounds, molecules that are not... necessary for their primary growth, but they're extra. The secondary compounds could be toxins that keep herbivores or pathogens away.
And some of them then we use as spices. So black pepper is a compound called piperine that's distasteful. Thinking you over pepper something. It's like having too much pepper so it's distasteful to things that would eat those leaves. Chili peppers.
You can actually keep your cat from eating your plants by putting a little hot sauce in the soil. Right? Not too much.
You make your cat sick and then you clean it up cat. But... So the chili pepper, the capsaicin that's in chili peppers is distasteful. They actually use it sometimes around the edge of crops.
They plant hot chili peppers so that deer and other things that would eat the crops stop at the chili peppers and don't come in to the crops. And of course, God bless caffeine. And then some herbivores involve ways to deal with the chemicals.
So we, as herbivores, just chop them up in little pieces and only use a little bit of the dead. You ever accidentally eat one of those tiny little red peppers? Ben is always having fun with me and not me eating one of those little tiny red peppers.
Alright, so here's an example of butterflies using one of these compounds. The Peloponnesian butterflies feed on passionflower leaves when they're casual. And they store the cyanide that the leaves have in them to discourage other herbivores. Butterflies store it, and now the butterflies poison anything that we're trying to eat.
It's a worm that we're trying to eat. Some passionflower species have these little leaf structures, little things on their leaves that look like butterfly eggs because then a female will not lay her eggs if she thinks there are already eggs there. She won't want her eggs to be competing with the other eggs. So this is one of those back and forth.
The leaf evolves cyanides to turn predators. The butterfly not only isn't affected by the cyanide, but stores it and uses it. Then the leaf develops these little spots that deter the butterflies.
Are the leaves and the butterflies having little conferences among themselves, deciding to do these things? Of course not. So how did the first leaf end up with these spots? How did we get a mutation?
How do you get new things, new combinations, new genetic traits? Mutation or recombination? They've got to die over. It's either a mutation or it's genes that were kept separately because they were on different chromosomes or they were only males or something that got together because of sexual reproduction. What's the other way of saying mutation?
Recombination. So the other interaction I want to talk about in these terms is mutualism. Keep in mind that... In 99.9% of cases animals are suffering. Things evolve, things get passed down generation by generation and may change and evolve and adapt because that individual is having babies.
And the individuals that share that trait have more babies than others. So in a mutualism, Each partner is not being nice. They're participating in that mutualism because it helps them leave behind more offspring. So species benefiting another species are acting in their own interest, and it happens to benefit others.
It's not altruism. Altruism is when... One individual or species is doing something that benefits another and it actually hurts the actor. So most pollinators visit flowers to get food. They happen to move pollen around at the same time, but the flower is providing food to lure the animals so that pollen can get moved around.
Nobody's actually just doing it out of the kindness of their little flower heart. The example that the book goes into in detail is leaf-colored ants. And so there you can see the ants actually carry these leaves that are as big as they are in their mandibles. And then they follow in little trails.
And they take these leaves back to their nest. And then back in the nest, they're using the leaves to grow this fungus. So some ant colonies provided more food and were growing productive fungus so that they had more food for the eggs and the pupa to develop than other colonies did.
So this behavior of taking care of the fungus evolved through natural selection. Okay. And these ant nests and colonies are huge in the tropics. Okay.
So that wraps up chapter 40. We have questions about chapter 40. Yep. When we get our test right, like, is it, when we're talking about international, are you going to give us like questions that we know? Like, like animals that we know?
Yes. I will not put examples without making sure that you know what the animal is. Okay. So chapter 41. She's now kind of taking the idea of the community and expanding it a little bit. Instead of looking at how one species interacts with another, we're now looking more at a whole assemblage of species.
A whole bunch of species together and how that community functions. So we already know that community is a group of species in one area and we depend on communities for natural resources and services. We'll talk more about that later, like what actually we get out of it.
But a lot of this is going to be about community structure and function. So structure meaning which species are there, how many of them are there, and then function being how energy is flowing through that community, how those species are interacting, and that kind of thing. And of course, we're going to use all this information to try to keep them all alive. Now keep in mind that when we say community and when we're defining a community, the boundaries can be kind of arbitrary.
Like we decide what the boundary of the community is. So you know if you're looking at a lake, most of the things that live in the lake can't live outside the lake. So that's kind of the community of fish that are in the lake.
But if you're looking at... Something like the frog species that are in the lake, they're laying their eggs in the lake, but then they're going up on land. So where's the boundary of that community?
Is it just the lake, or is it the lake and the surrounding land? So we define kind of what communities we're talking about, because rarely is it just at strict boundaries. And sometimes we just look at one group of species, like just the birds.
Like these are all the birds in Florida. And we look at how the birds interact with each other. So the boundaries are a little fuzzy in nature.
We define them so that we can study them. So the structure that we talk about is the community composition. How many species?
The identity of those species, what are they, and the abundance. How many individuals of each species are there? And how do those species get there or why are they not there? Because they either colonize that area or they go extinct.
So the species that are in a particular community get there when that area is colonized, when the first individual arrives. They persist for some period of time. And then they go globally extinct. So, just like we think about the number of individuals is births minus deaths, the number of species is colonizations minus extinctions. So, the change in the number of species.
Over time, then we start off with 50 species on an island. And three more species arrive during the year, but two of them go extinct. Then our chain species number was one. Same kind of math, now we're just looking at the number of species instead of the number of individuals.
Now these local extinctions, so keep in mind 99% of every species that ever existed has already gone extinct. Local extinction can be just natural or of course becoming a complex. But you need to separate in your brain local extinction from forever extinction. Local extinction is the orange is the historic range. This is a tiger.
So that area up there, that went locally extinct. There are no more tigers up there, but these little yellow patches down here, there are still tigers on the planet. They just went locally extinct. They could be gone for right now, they could be gone forever. The point is that it's just in that area.
They still exist somewhere else on the planet. So in order for them to come back to that orange patch, some from that yellow patch would need to move over there. So that would be a new colonization. So local extinctions, if the local conditions are not ideal or change, species can't tolerate them, they die out. Some resource might not be there, there's not enough food.
Or they get excluded, right, the competitive exclusion, when there's a better competitor or a good predator. Sometimes the population size is just too small. In the extreme case, you can think, if there's only two tigers, those two tigers can make babies. But then everybody's brothers and sisters.
There's nobody to make babies with that's not your brother or your sister. Your population is too small, and you have too much inbreeding. Bad genes get together, and it can wake you up. Wait, so inbreeding is one of the reasons why local institutions are...
I'm sorry? Like inbreeding? Mm-hmm.
That's one of them? Inbreeding is when the population is small, you have a higher risk of inbreeding. So when we look at species composition, which species are actually present, it can of course change over time with colonizations and extinctions, and it's going to change over space.
So as you go... Across space, you're going to get different environmental conditions, which means you're going to get different species. So, for instance, if we look at the side of a mountain, it has different vegetation zones. As you go up the mountain, it gets colder. The air is thinner, so up at the top you've got icy snow, and as you come down the mountain, you've got tundra, and then forest, and then deciduous forest, and then at the bottom you may have tropical rainforests if you're in the province.
So obviously the species that are in each of those zones is going to be different. If you move from the tropics up into the subtropics of the North and then up into the Midwest and up into the North, it gets colder. Species are going to change. One of the ways that we study this and that we measure this is with transects. If you're doing a study, you take measurements along a straight line, and a transect.
You're transecting the area. So if we look at species composition along a transect, it derives from different types of soil. This is in a fairly small area, but we're looking at the plants that are in soil that is serpentine, meaning it has a lot of heavy metals in it, or not. And what you can see here is that in the, so this is the sample along the transect.
So here's our line. At the beginning of our line, we've got the soils are non-serpentine, not a lot of heavy metals. We've got oaks and Douglas fir. Then at 10 meters to 15 meters we have a few Douglas firs but more of these Hawkweeds, fescue, and we start getting some live oak.
And then when we get into the serpentine soil soils that have a lot magnesium, nickel, and chromium there's none of these black oak or poison oak are left. These things can survive in any of them. They don't care if there's metals in the soil.
These are gone. And now we have predominantly yarrow, book brush, knotweed. So along the gradient of going from no heavy metals, medium heavy metals, lots of heavy metals, the species of trees change.
So that's what we mean by an environmental gradient. In terms of looking at how species come in and colonize an area and get wiped out from an area, one of the sort of classic studies has been the Takatoa volcano. The island is called Anak Takatoa and it erupted in 2018. 2018 this thing, it went off so that it looked like that before and it looked like that after. It was just nothing but burn.
After the volcano erupted. So it wiped out everything. Wiped out everything so then for the next two years scientists used this as a natural experiment to see when things started coming back.
There were 24 species of plants. If it was completely wiped out, how did 24 species of plants get there? Wind?
Or? Birds flying over and pooping them out. So either wind or bird poop. Brought seeds. Now what kinds of plants do you think would be the first to colonize this island?
So, not so many if it was moved out by birds. But what kind of environment is there on the island now that plants would have to be able to tolerate and grow well on what kind of environment? So the soil would be, have a very different composition, right? And there'd be lots of bright light. There's no shade, right?
Some plants like to grow in shade. Some plants like the bright light. So it would have to be what we call pioneer species. Pioneer species are the ones that get there first. And can grow in full sun in relatively empty areas.
And then as the pioneer species start to grow, and some grow a little bit taller, now there's some shade. Now the species that need a little bit of shade to get started have a little bit of shade and can start growing. And may out compete or outgrow the pioneer species.
So as trees grow up, the pioneer plants disappear because now the place is shaped. Then once forest develops, now you can have the fruit eating birds and bats actually stay at the island instead of just flying over. So it's this process of change as the environment is changed by the different plants that are growing.
And it changes the soil. And it's still 2024, this wasn't that long ago, right? So we're still monitoring the island to see how it changes over time.
Will it inevitably get back to the way it looked before? No. Why not?
Why wouldn't it, you know, this process of one thing replacing the next, we can kind of predict how the environment is going to change, so why can't we predict exactly what's going to be there? Exactly which species arrives, they're just floating in on the wind. It's not inevitable that the same species is going to be the one carried in on the wind first. There's an element of chance to all of it. Which species of seed bird is going to poop out onto the island and then grow?
Exactly, because the weather is also somewhat unpredictable, right? So it depends on how much it rains and how much moisture these things need. If the climate is in the process of changing, then that could impact long-term change.
So yeah, exactly. So... Species composition, just like when we talked about population growth rates, are dynamic. It changes over time, depending on who's coming and who's going. We have an ongoing colonization and local extinction.
And we get this turnover. So in general, we're going to have a pioneer community. We'll start off with a native island, and then grasses, herbs, shrubs, and then taller trees and forests, and then you can go to more of a evergreen forest, what's called a climax community. What's this process called? Anybody?
Succession, it'll be in writing in a couple slides. So this is changing over time. Yeah.
So that would be the ultimate community that would be there if... There were not unexpected weather changes. If there were not, anything would knock it back again. So what knocks it back again?
Some kind of disturbance or change, and we'll talk about that in a minute as well. So a lot of this, you see when we talk about this, we focus on the plants, we focus on how the plants and trees are changing, because the animal, they're the base of the food chain, right? Without plants, you're not going to have any animals.
So we focus on the plants, but of course then that determines the food and what we call the habitat structure. The habitat structure basically is the different sizes of plants, the shade that they create, the physical structure. So like these ungulates in Africa, they like to be where there's not a lot of plants because they want to be able to run in big curves. They're in open areas where they can run like the wind in a big curve.
Bird species, they want to be someplace where there's plenty of trees, so not only do they have food, but they can hide. And there's going to be plenty of insects for them to eat. So in some cases, it's not necessarily the identity of the plant, but the physical structure that it creates in the habitat. To her point, what knocks it back?
What keeps it from getting inevitably to that? Sometimes it starts. So some event that causes a sudden environmental change. So if species are replacing one another in a predictable sequence, we call that succession. From...
Pioneer species to the intermediate shrubs to the climax community of a mature oak and jigger forest. Can you repeat the part about the species? The way they replace one another? Definitely. So basically this idea, species replacing each other in a predictable sequence, is what we call succession.
What interrupts succession and makes it not necessarily reach this climax community is some kind of disturbance. Yeah. So, let's say, go back to the volcano.
So let's say the volcano is in the plant community, I've reached the climax community for the emerald scundag or emerald scundag as the pioneer species. The animals will come back as the primates come back, right? Because there's going to be insects that can feed on this, right? And insects can get blown in on the wind too, right? And then there's gonna be lizards that can eat the insects and birds that can feed on the insects.
So they'll come along as well. And of course, what's gonna determine what kind of climax community it is? The type of animal and whether the climax community is a coral reef or a deciduous forest or a tropical rainforest, that's going to be the environment, the bio.
I need to take my clippers so I don't have to walk around so much. Okay, so after a disturbance... Succession often leads to a community that resembles the original one, often.
But, as we said, the return of that original community is not guaranteed because we could have another disturbance. Or we have that element of chance of which species actually arrived. But we can also get new environments on a smaller scale. Boop.
Boop. On a smaller scale, so it's not necessarily a major disturbance like a volcano erupting. Sometimes it's just something like a glacier melting.
Or a depression fills with rainwater, you make a new mud puddle. A mammal poops. So, for a dung beetle...
A patch of elephant dung is a new piece of habitat. So, an elephant takes a poop, and now the dung beetle can colonize... That and there's a lot of different species of dung beetles.
So those species will change over time as the dung dries up. You didn't know we were so much in here, did you? So this is over time.
As the dung ages, so the elephant first crafts, we have one set of species that like the fresh, wet, speedy dung. And then as it starts to dry out, there will be different species that come in. And then as it gets even older and drier, There's different species that come in, and the first ones leave.
So there's a lot of different species of animals? Yes, there's a lot of different species of animals. So this is just an example of that same idea of succession, but in animals.
So how come the tunas are the only ones that stay the full life? Because they take the dung down into the ground where it doesn't dry out as fast. So they can keep the moisture because it's not up in the sun dry now.
So the greens are the rollers, right? And once it's dried out, you can't roll, right? And then the dwellers are the ones that actually kind of stay with it, live in it, as opposed to rolling it away or tunneling it down. And we do have, and if you are intrigued, we do have a professor here who studies Florida thumb beetle. And so if you've got some research experience, you can learn all you ever wanted to know about dog beetles and the types of their systems.
Okay. No, that's just a cool stuff. Okay. So what factors are going to result in these successional sequences?
What makes these changes happen? Well, for one thing, some species are better colonizing than others. Some species are better at getting there first and surviving those early conditions. So the plants that like bright sun, early arriving Dung Needles tend to be the ones that are strong flyers, so they're moving around searching, good sense of smell so they can find it. Or they ride around on the back of the elephant, waiting for it to come.
On Trachycella, the first plants are the species that have seeds that are easily dispersed by wind, so that they can get there. Now the... Another thing that can mean that you never reach that climax community is there's a disturbance that's so extreme that the environment can't bounce back. The environment can never go back to what it was. So if the disturbance pushes the system past a threshold or tipping point, we call that a state transition to a distinctly different community.
This is often what we do with things, as humans. Right? So, the borderlands, the Mexican borderlands that was the example in one of the previous chapters. If we had raised capybaras, by the way, or goats, on that land and ate the grass, once we removed the capybaras or goats, the grass didn't grow.
because the seeds are still there in the soil. But POWs are so heavy, and we tend to have so many of them in one small area, they trample the ground, pack down the soil, water can't infiltrate the soil for plants to grow, and the roots of the plants can't bury into the soil because it's too compact, and so the grass has never come back. So we changed it from a grassland to this shrubland. Climate change is another example of this, right?
As opposed to the weather, which is temporary, and things come back, when we change climate, which is on these huge, long time scales, they tend to have a more permanent shift or a more permanent change. So, for instance, if we're thinking about a species that right now lives here in Florida. But as temperatures raise, so they like it hot. As global temperature raises, then they can move up in where they live.
Now they can survive in the Midwest and in the Middle States because now it's warmer there. So now it's warming up for them. So we have, and then species that used to live further south are moving up here and competing with the Florida species.
So they may not be in Florida at all, they might completely move. It could expand their distribution or it could just move it altogether. And we see examples of this already with some lizards and some birds, that their territory, their distribution is shifting according to climate change. One of the ways that we study this, because we're talking about stuff going back hundreds of thousands of years, we want to know what's been happening over these long time scales, is this is a pack-up.
Black rats really do hoard stuff. Like they collect things and take them back to their nest and leave behind then kind of trash. What they bring back to their nest they can't eat. And emitted is basically their little trash pile.
And so in that midden, basically fossil middens, okay, so trash left behind by pack rats, hundreds of thousands of years ago, we can look at fossil plants. And we can figure out what plant distributions were 14,000 years ago. When we're looking at this little area down here between Arizona and New Mexico, 14,000 years ago, based on the seeds and plant fossils that were found in these pack rat middens, it would have looked like this.
Today, it looks like this. Now since this was 14,000 years ago, we can't blame this one on us. This is natural shift over time.
Does that make sense? So I said before that what we're interested in is community structure and function. How structure relates to function.
So this is where we'll pick up on Monday. When we're talking about structure, we're talking about both abiotic and biotic. What the physical environment is and what the general groups of species are.
And then functions like how the web works. How energy is flowing. We'll talk about the geochemical cycle.
Thank you.