OFFICIAL14 According to the professor, how do decomposing leaves affect microclimates?

[00:00.00]NARRATOR: Listen to part of a lecture in a biology class. 
[00:05.08]FEMALE PROFESSOR: Almost all animals have some way of regulating their body temperature; otherwise, they wouldn't survive extreme hot or cold conditions. [00:13.75]Sweating, panting, swimming to cooler or warmer water, ducking into somewhere cool like a burrow or a hole under a rock … these are just a few.
[00:23.38]And that spot is colder or warmer than the surrounding environment because it's a microclimate. [00:29.99]A microclimate is a group of climate conditions that affect a localized area—weather features like temperature, wind, moisture, and so on ... [00:39.31]And when I say localized, I mean really localized, because microclimates can be, as the name suggests, pretty small, even less than a square meter. [00:49.06]And microclimates are affected by a huge number of other variables … [00:53.42]obviously weather conditions in the surrounding area are a factor.
[00:57.21]But other aspects of the location, like, uh, the elevation of the land, uh, the plant life nearby, and so on, have a substantial effect on microclimates. [01:07.81]And, of course, the human development in the area … um, a road'll affect a nearby microclimate. [01:14.14]It's also interesting to note that microclimates that are near each other can have very different conditions … [01:20.77]in the forest, for example, there can be a number of very different microclimates close to each other because of all the variables I just mentioned.
[01:28.88]MALE STUDENT: So how does a hole in the ground, a burrow, stay cool in a hot climate? 
[01:33.47]FEMALE PROFESSOR: Well, since cold air sinks, and these spots are shaded, they're usually much cooler than the surrounding area. [01:40.99]And these spots are so important because many animals rely on microclimates to regulate their body temperature.
[01:47.94]Umm … for instance, there is a species of squirrel in the western part of the United States [01:53.44]that can get really hot when they're out foraging for food, [01:56.58]so they need a way to cool down. [01:58.79]So what do they do? [02:00.07]They go back to their own burrow. [02:01.91]Once they get there, their body temperatures decrease very, very quickly. [02:06.25]The trip to the burrow prevents the squirrel from getting too hot.
[02:09.67]MALE STUDENT: But squirrels are mammals, right? [02:11.37]I thought mammals regulated their temperature internally …
[02:14.82]FEMALE PROFESSOR: Mammals do have the ability to regulate their body temperature … [02:18.76]but not all can do it to the same degree. Or even the same way. [02:23.36]Like when you walk outside on a hot day you perspire and your body cools itself down—a classic example of how a mammal regulates its own body temperature.
[02:32.66]But one challenge that squirrels face, well, many small mammals do, is that because of their size, sweating would make them lose too much moisture. [02:42.69]They’d dehydrate. But on the other hand, their small size allows them to fit into very tiny spaces. [02:49.46]So for small mammals, microclimates can make a big difference—[02:53.82]they rely on microclimates for survival.
[02:56.53]MALE STUDENT: So cold-blooded animals, like reptiles—they can't control their own body temperature, so I can imagine the effect a microclimate would have on them… 
[03:05.00]FEMALE PROFESSOR: Yes. Many reptiles and insects rely on microclimates to control their body temperature. [03:10.80]A lot of reptiles use burrows … or stay under rocks to cool down. [03:15.55]Of course, with reptiles, it's a balancing act. [03:18.85]Staying in the heat for too long can lead to problems, but staying in the cold can do the same.
[03:24.20]So reptiles hafta be really precise about where they spend their time, even how they position their bodies. [03:30.16]And when I say they're precise I mean it—[03:32.77]some snakes will search out a place under rocks of a specific thickness, because too thin a rock does't keep them cool enough and too thick a rock will cause them to get too cold. [03:42.69]That level of precision is critical to the snake for maintaining its body temperature.
[03:47.50]And even microscopic organisms rely on microclimates for survival. [03:51.96]Think about this: decomposing leaves create heat that warms the soil; the warm soil in turn affects the growth, the conditions of organisms there, [04:02.15]and those organisms then affect the rate of decomposition of the leaves …
[04:07.07]So a microclimate can be something so small and so easily disturbed that even a tiny change can have a big impact. [04:14.80]If someone on a hike knocks a couple of rocks over, they could be unwittingly destroying a microclimate that an animal or organism relies on.