Interactions Among Organisms p. 1040-1042

Competition relationship between organisms that strive for the same resources in the same place resources might be food, water, or space two different types of competition: Intraspecific - between members of the same species Interspecific – between members of different species

Symbiosis a close relationship between two species in which at least one species benefits for the other species, the relationship may be positive, negative, or neutral Three types: 1. Mutualism 2. Commensalism 3. Parasitism

Mutualism: 2 organisms living together in such a way that both benefit. Examples: clown fish & sea anemone Nile crocodile & Egyptian plover

2. Commensalism: 2 organisms living together in such a way as one benefits & the other is not affected. Examples: Hermit crabs, mites

3. Parasitism: 2 organisms living together in such a way as one benefits (the parasite) & one is harmed (the host). Examples: Ascaris lumbricoides, ticks

Predation Relationship between organisms in which one preys on the other Prey have evolved defenses against predators Horns, spit, quills, obnoxious odours, ink, poison, camouflage, armour, stingers, etc. Predators evolved counter-defenses: Strong digestive juices, poisons, camouflage, speed, good sense of smell/hearing/sight, antitoxins, etc.

Develop predator-prey cycles: Prey becomes numerous b/c more prey, predators grow & reproduce  more predators b/c more predators, # prey deaths > # prey births & prey population drops b/c prey #s drop, predators starve  predator population drops b/c fewer predators, prey survive & reproduce  prey population grows Cycle repeats

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