Listen to part of a lecture in a biology class, when you see a mushroom growing in the forest, you\'re actually looking at just a small part of a much larger fungus。 underneath the mushroom, underground。 you\'ll find the rest of the fungus a network of thread like structures. These individual thread like structures are called hyphae。 and the network of these hyphae is called a mycelium. In some cases, my Celia can be huge structures weighing hundreds of tons. We\'ll go into more detail about them later this week, but for now, you have the basic idea. Okay, back to the mushroom on the surface. The mushroom is the fruiting body of the fungus. Its primary function is to produce and nourish spores. Spores are to a fungus what seeds are to a plant. They\'re the reproductive bodies. Spores are tiny, most of them consisting of just a single cell. Now, if you knock a mushroom over and look at the under surface of the cap. it\'ll look something like this. The flat, thin structures that you see radiating out from the center are called gills. and it\'s deep inside these gills that the spores are produced. Once the spores mature, they\'re released. and they fall down through the spaces between the gills and out into the air below the cap. where they can be carried away by the wind. hopefully to some location that\'ll give them at least some chance of surviving, of developing into a mature fungus. Now, when the mushrooms in its normal upright position, the gills have a nearly perfect vertical orientation. Why does that matter? Well, when the spores are released, gravity pulls them straight down. So if the gills didn\'t have this orientation. the spores would be forever bumping into them as they fell. And these spores are very sticky. so if they come into contact with the gills, they\'re going to stick to them. and they\'re never going to go anywhere. Okay, so what do you think of the mushroom strategy, if you will, for dispersing its spores? Jennifer. It seems like a good system. You\'ve got a stock raising the cap above ground so the wind can get under it and carry the spores away. And you\'ve got these, like, tiny little spores that are really light, so it doesn\'t take a lot of wind to carry them. Yes, the system looks well designed. but despite this seemingly efficient design, mushrooms have to produce millions, even billions, of spores. Why so many? Well, it turns out that many spores are not carried very far. they land within a meter or so of the mushroom. but that\'s an area where, as we said, there\'s already a mycelium established underground. So that\'s not a suitable area for a new fungus to grow. and some of the spores get carried farther, but many of those land in inhospitable habitats. Oh, okay. but fungi that do not depend on the wind. that disperse their spores in other ways, can have a much higher success rate. For example, some of you may be familiar with truffles. Some species of truffles are edible and considered delicacies. like the mushrooms we just discussed. A truffle is the fruiting body of certain species of fungi. Unlike mushrooms, however, truffles grow underground. and the primary mechanism they use to disperse their spores is very different. You see, it\'s not just humans that like truffles. As a truffle spores mature, the truffle develops an aroma that attracts many kinds of animals. In fact, Europeans have for centuries been using pigs to locate and extract truffles. Recently, they\'ve begun using dogs instead of pigs. As dogs are less intent on eating the truffles they find. Also, most people would rather spend their time with dogs than with pigs. Anyway, when a wild animal, say, a deer finds some truffles and eats them. The spores remain intact in its digestive system. The deer then walks on for a while, and at some point, it\'ll excrete waste from its digestive system, and the truffle spores will get deposited in that new location. Yes, Eric. So how is that more efficient than the way mushrooms disperse their spores? Well, the deer carry the spores a nice distance away from the original truffle right. to habitats that are conducive to the growth of truffles, right? Whereas the wind might not pick up the spores at all, or might deposit them in like the middle of a Lake or something.