Herbivore Defenses

Jason Amores Sumpter
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While some animals air content thio eat the fruits and nectar of plants, others want to eat the important, often vital structures of the plants body. This could be potentially life threatening to plants, which is why they've come up with a number of measures to defend against herbivores. Now, some physical external measures include thorns, which you can see here and is a type of modified stem spines, which you can see here in this cactuses characteristic needles and spines recall or a modified type of leaf. And also they'll use try combs, which you can see here covering the leaves of this plant. They're kind of scattered all over the leaves here, and these contains some nasty chemical surprises for the ER Before. Now, plants will actually use what are called secondary metabolites. These air like chemical weapons against herbivores, and they will have ah, number of effects. Sometimes they just smell bad. Other times they'll actually poison the animal, and sometimes they can actually alter the animal's nervous system. And some of you out there might recognize what this plant is behind my head. That is cannabis. People often like Thio, use it recreationally, but the chemicals in the plant were actually intended to ward off herbivores. They're going to mess with the nervous systems of herbivores and, for example, with insects can be super super toxic. So, uh, you know that is really the intention behind those chemicals in cannabis, it's to kill or just make sick or ward off herbivores. Now, if herbivores can get past those outer defenses, plants have some other surprises for them. Plants will have. Some plants will use what are called Proteus inhibitors thes block, digestive enzymes found in animal saliva and stomachs. So if an animal eats a bunch of a plant with Proteus inhibitors, it's going to get sick because it's not going to be able to digest the material it eight from the plant. Believe it or not, if you don't have the proper enzymes in your gut, uh, to digest the food you put in your body, you'll get very sick. Your body will reject that, and herbivores have actually learned to recognize the taste of protease inhibitors now in, uh, you know, because producing these chemicals can be costly for the plant, they don't want to do it willy nilly, so there's actually a hormone signal that plants used to produce or to signal to produce protease inhibitors. And this is called system in. This is a hormone, ah, hormone that wounds will signal, and it again leads to the production of protease inhibitors. So basically, if a herbivore takes a bite of your body and you have a wound, it's going thio. Trigger the release of system ins, and that's going to produce protease inhibitors. So hopefully the herb of or if it continues to eat the plant will taste those protease inhibitors and be like, No way. I'm not getting sick. I'm out of here. I'm done with this plan now. Sometimes plants can go a step further and get downright sadistic with their defenses and probably the creepiest. Let's say example of this is with caterpillars and wasps. Well, it's it's believed that when some plants like, for example, this here are being eaten by caterpillars. These caterpillars are having a field day just munching on that plant leaf that the plant will actually give off a chemical attractant that will draw wasps to them. This is because wasps are actually for some wasps are parasite toys. That means that they live freely as an adult, but they are parasitic as larva and in fact, wasps lay. There are some wasps lay their eggs inside caterpillars, and when the larvae hatch, they eat the caterpillar from the inside out. And that is what this disgusting images behind my head. You can still kind of see the shape of the caterpillar, but all that's left is these gross little wasp larvae that have just completely eaten it away. Pretty gnarly, horrific stuff. I mean, that is truly going medieval on someone's ass. So it is a war zone out there, and plants have to take all the defensive measures they can, especially considering that, unlike animals, plants are unable to move. They've got a plant. Forgive the pun. They have to plant themselves where they are and mount a resistance and mount a defense. That's all I have for this video. I'll see you guys next time