5.2 Interactions & Communities I. Predator-Prey Interactions A. Predation- one organism killing another for food B. Most organisms are both predator & prey 1. Predators come in all sizes, even microscopic C. Coevolution 1. Species involved often develop adaptations in response to one another a. predators evolve to be more cunning to catch prey b. prey evolve to be faster runners to escape more easily

D. Parasitism 1. one organism feeds on another 2. Host a. usually larger than parasite b. harmed but not killed c. try to defend themselves with immune system or by scratching 3. Parasite a. depends on host for food b. also needs host as place to live c. ex- fleas, ticks, tapeworms, etc.

E. Herbivory 1. Animals that eat plants 2. Do not usually kill the plants 3. Plants do try to defend themselves a. ex- spines or thorns b. chemical compounds 1. leave bad taste, make animal sick c. Monarch butterfly caterpillars 1. Eat toxic milkweed plant 2. Does not harm caterpillars but makes butterfly inedible to birds

II. Other Interactions A. Symbiosis 1. relationship in which two species live in close association with each other 2. one or both species can benefit 3. Mutualism a. Both species benefit

4. Commensalism a. one species benefits & the other is neither helped or hurt