Lecture 6

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Biological Sciences
Herbert Kronzucker

BGYC61H3 Lecture 6 October 20 2008 Recap We finished discussing the importance of chemical factors in determining herbivory from taking effect. All organisms die and decompose (pig example) and the importance of community ecology that occurs when things decompose. There are chemical factors that prevent the rapid decay as well as preventing organisms being feasted upon while they are still alive. We talked about plants predominantly (alkaloids). If there are pharmacological affects that will affect the feasting animal then they wont eat it i.e. caffeine, nicotine, and morphine will have quite sophisticated affects on the CNS. They are all addictive as well as you know. There are 1,000s of chemicals that are routinely produced by plants. Microbes, fungi, algae, and animals also produce chemicals to prevent feasting by predatory organisms on them. The most sophisticated arsenals are made by plants probably because they cant run away from anything. Saplings have to have some defence or they will be eaten completely. We used the example of the Moose and how it wouldnt eat the whole meadow. The plants will mount a defence because they will produce a higher amount of chemicals to keep from being eaten. The responses can be rapid and happen within hours and over several days in most plants the differences can be measured to repeal feeding in those environments. In BGYB50 we talked about how plants in this environment here probably wouldnt be affected by herbivory. Most biomass produced by plants stays put. We talk about transit time of biomass and how fast that can be. Aquatic ecosystems are usually not endowed with chemical defence and as a result they are predated upon by others. They are eaten very quickly. Organisms that perform photosynthesis will channel the majority of their biomass into the food chain. On land the majority of biomass will not flow through this food chain but most of it will fall prey to the detritol food chain. It will take longer for the maggots to begin to invade a plant corpse if it is full of these chemicals. The sophistication that has evolved in the 500,000 plant species (most havent been named in Latin as of yet 50%). There are millions of chemicals out there that differ a little. They are all based on aromatic chemistry that has 1 or several Benzene rings in them. You will always find nitrogen bound to carbon to the ring itself or by a side-chain. A methyl group next to nitrogen is common. There is a striking similarity between Hordenine (Barley plant) and the chemicals in your body i.e. Dopamine. The plants know when something is feeding on them and they will produce a feeding repellent. Plants can produce many of the same chemicals (neurotransmitters) in our bodies. If they dont directly produce these neurotransmitters then produce chemicals that are similar i.e. Epinine and Hordenine and they mimic the acts of Dopamine (different by only 1 methyl group). If you eat any of these plants your body will feel that it wants more because your gut is confused but after a while, as it feasts longer, the other neurotransmitters will make you feel queasy before you have actually eaten too much. There are many papers that are written BGYC61H3F.October.20.2008 Lecture 6 1 www.notesolution.com
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