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- Predation: predator kills and consumes all or most of another organism (prey)- Defense from Consumption- Prey evolve defenses to counter predators- 2 basic types of defenses- Constitutive: always presented- Inducible: produced in response to predators- Camouflage: blend into the background. Ex: flat fish- Schooling: safety in numbers- Weaponry: fighting back. Ex: porcupine- Mimicry: constitutive defenses that led to 2 types of mimicry.: Mullerian mimicry: species with similar defenses resemble each other: Bastein mimicry: species with defenses resemble those with defenses- Mullerian can protect both dangerous and harmless species- [Mullerian] Sting Ex: common wasp, bee (bumble), Honeybee- [Bastein] Doesn’t sting Ex: hornet moth, wasp beetle, hoverfly - Inducible Defenses- Variable responses- Triggered by presence of predators- Defense represents a fitness cost- Inducible defense minimizes fitness cost- Ex: cottonwood tree felled by beavers (re-sprouted trees, have more defensive compound)/ Mussels and Crabs- Top down vs. bottom up control of consumption
- Predators/ prey population undergo cycles- What control these cycles?- Bottom up: amount of prey regulate predator abundance- Top down: predators control prey abundance- Ex: the hare-lynx population cycle every 11 years, on avg. the size of the lynx population lags behind that of the hare.- Population of cycles of the snowshoe hares are influenced by their food supply as well as by interactions with their predators.- Mutulaistic Interactions(+/+)- Both organism benefits- Not cooperative or altruistic- Rare case when 1.) both organism attempt to profit 2.) both are successful- Many change to consumptive/competitive relationships- Ex: clown fish and anemone / mutualism between cleaner shrimp and fishes- Ants and acacia tree: ants defend tree from grazers, tree provide ants with home and food, so both have benefits.- Indirect Directions- 2 species that do not directly interact exert influence on each other- Influence is indirect- Consequence of interaction with another species- Indirect Interaction- Trophic Cascade (Ex: otter urchin kelps) (picture in class notes) - Keystone Species:Mar. 5. 2010- Species with effects on communities those are disproportionate to their biomass- Ex: small parts of organism but big impact- Tend to be top level predators- Species Diversity- Key feature of communities - Can be measured in two ways- Species richness = total number of species- Species diversity = weighted measure that includes both species number and abundanceCommunity 1Community 2Community 30 0 0 0 0 0 0 0 0 0 00 0 00 0 0 000 0 00 0 0 000 0 00 0 0 00 0 00 0 00 0 0 00 00 0 00 0 0 0- Species richness = 665- H (species diversity) = 0.590.780.69- Cause/ Role of Species Diversity
- Why are some communities more diverse than others?