4-2 Niches and Community Interactions

The Niche

• Niche – Where and How something lives; its role– Habitat is the organism’s address– Niche is the organism’s occupation

Community Interactions1. Competition

• Organisms compete for resources

Ex: Food, Mates, Shelter

• Competitive Exclusion Principle – no 2 organisms occupy same niche at same time.

2. Predation• One organism (predator)

captures and feeds on another (prey).

Battle at Kruger Lake

Community Interactions3. Symbiosis

• Mutualism – both benefit Ex: Flowers & insects Egrets & Alligators

Clown Fish & Sea Anemone

• Commensalism – one benefits, the other is not helped nor harmed Ex: Barnacle & Whale

• Parasitism – one benefits, other is harmed Ex: tapeworms, fleas, ticks,

lice

Keystone Species – essential to the balance of an ecosystem, change in their population can cause a

dramatic change in the community.

Dung Beetle Otters and Kelp

Ecological Succession

• Ecological Succession - change in an ecosystem1. Primary Succession – no soil (volcanic eruption or bare

rock)

– first to appear are “pioneer species” Ex: Lichens

2. Secondary Succession – Soil Exist (wild fires, clear cutting, plowed for farming)

3. Succession in a Marine Ecosystem – happens when a large whale dies and sinks to the bottom

4. Climax Community – fairly stable, mature, dominant community established after succession.