Post on 30-Dec-2015
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.