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