Community Ecology Chapter 52

Community:  All the populations in an ecosystem  Difficult to study  Can be large or small  Have a wide range of interactions  Are rarely isolated

Community structure and functioning  Niche vs. habitat Niche = role Habitat = local environment (part of an organism’s niche)  Fundamental niche – all the basic parts of the ecosystem that it could use; reduced by competition with other species  Realized niche – the parts of the ecosystem that the organism actually uses

Interspecific competition  Two or more species attempting to use the same limited resource  Competitive exclusion: two species cannot share the same resource at the same time – one will be excluded Resource partitioning – competing species each use only part of the available resource so they can coexist Character displacement – a physical change in an organism’s appearance as a result of competition reduction

Predator/Prey  Coevolution – each one changes in response to the other  Predator strategies: pursuit vs. ambush  Prey strategies: Plants – physical or chemical defenses Animals – physical, mechanical, chemical, cryptic coloration, mimicry

Symbiosis  Mutualism – both benefited Nitrogen-fixing bacteria and legumes  Commensalism – one benefits, the other is neither harmed nor helped Tree and epiphyte  Parasitism – one harms the other Tapeworm and host

Keystone species  A crucial species – determines the characteristics of the rest of the community  Many times are the top predator in the ecosystem  Without their presence the shape of the entire community changes

Dominant species  Also greatly impact their community – but because of their high number  Forests – trees, coral reef - coral