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Ecology Lec 13 summary- predation & herbivory.docx

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Biology 2483A
Hugh Henry

Ecology Lec 13 summary- Predation & Herbivory Over ½ species get energy from eating other- Exploiation interactions (+/-)- one benefits, other suffers 3 categories: - not clear cut- e.g. wolves can eat animals or nuts & berries 1. Herbivore-eat tissue of plants or algae- usually don’t kill Herb/pred.: feed on multiple organisms 2. Predator- kills & eats other organisms (Prey) in their life VS parasite- usually 1 3. Parasite- lives in or on host organism- usually doesn’t kill - some parasites are pathogens- cause disease Parasitoids- insects that lay egg in or on host, & larvae hatch inside, eat and kill host Predators - Actively foraging- follow prey where there is abundant prey - Sit-and-wait predators- relocate from time to time - Most predators (eat large variety of prey species) VS Specialist predators (prefer one or two) - Prey switching- Eat disproportionately more of the more abundant prey 1. Search image- see them more, therefore search for them more 2. Become better at capturing the more abundant one Herbivores - Most herbivores- feed on narrow range of plants (1 or 2) - grasshopper- many plants, Large browsers switch between species in diff seasons - Eat diff parts of plant- some specialize in particular parts - leaves & seeds more nutiritious - Prefer N-rich parts- animals (more protein), plants (more carbs, less N - seeds come close to animal N level - Effects on plants 1. Reproductive success- eat seeds, less success 2. Survival- Nutrients lost- eat sap/sugars/fluids 3. Growth- Roots lost- less ability to absorb nutrients Strong selective pressure by herbivores/predators = Prey evolve adaptations Prey adaptations - Physical defenses- Large size, rapid movement, body armor - Crypsis- camouflage to resemble environment - Aposematic coloration- creates toxins & advertise using unique colors/patterns - Mimicry- mimics an organism that is toxic/dangerous to scare predator - Behavioral adaptations - not forage in open areas - keep lookouts- sharing cost of looking out - defensive circles - Tradeoffs between behavioral & physical defenses - e.g. snails- thick shell (hard to break) but slow to escape; thin shell opposite Plant defenses - Masting years- hide seeds, and the put out so many to overwhelm the herbivores - Compensation- eating plant tissue stimulates growth - Full compensation- no net plant loss by end of season - e.g. Remove shading of bottom part Remove apical dominance, less suppression signal, more growth of bottom - only works if removed early in seasons - Structural defenses- tough leaves, spines, thorns, hairs
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