“Who are the people in your neighborhood?” Interactions between organisms Roles in Ecosystems Niche = The “job” of an organism in an ecosystem Described using Where organism lives/carries out “job” Some words: habitat, biome, etc. How organism obtains fuel (food) Some words: Producer and Consumer, autotroph and heterotroph, herbivore and carnivore, predator or scavenger, etc… For Example • The Waterstrider – top-water predator of small animals on the surface of the water Types of Interactions There are several different ways organisms can interact. Predation • A trophic (feeding) relationship where one organism eats another, killing it. • Other trophic relationships are herbivory and detritivory Consuming dead organisms Hawk photo from: http://www.flickr.com/photos/jurvetson/226587515/ Consuming plants Competition The struggle for limited resources Carrying capacity = The maximum number of organisms that can be supported by available resources Competition When populations rise over carrying capacity (increase in population or decrease in resources) more competition Interspecific = between 2 different species Intraspecific = between same species Symbiosis Living together When 2 different species live in a close, inter-dependent relationship. At least one member of the pair benefits. Symbiosis Mutualism: When both organisms benefit; What most people think of as “symbiosis”. e.g. Lichens, coral Commensalism: One benefits by eating unused food, the other is unaffected e.g. gut bacteria, remora and sharks Parasitism: One benefits the other is harmed (not killed) e.g. tapeworm, ticks Altruism One organism helps another organism but gets no benefit, risks harm or is harmed in doing so Being “nice” Common in some birds Can be intraspecific or interspecific Beware of anthropomorphisms! Fairy wren photo: http://commons.wikimedia.org/wiki/File:Superb_fairy_wrens_mark_2.jpg Let’s look for some interactions! Yep………. It’s Lab time!