Community and population APES

Indicator species

Plant, animal, microorganism who’s absences/presences act as a sign of an environmental condition. They are sensitive to changes in their environment, indicating the health of the ecosystem. Ex: Moss = poor acid soil, Algale bloom = excess nutrients

Keystone Species

An organism such as a plant or animal that plays a key role in holding its ecosystem together Ex: Sea otters help protect kelp forest)

Foundation species

Plays a major role in creating, shaping, maintaining an ecosystem

Law of competitive Exclusion

No 2 species can occupy the same niche (role)

Emergent layer

Very top layer consisiting of the tallest trees which tower above everything else

Canopy

Middle layer

Understory

Middle bottomish directly below the Canopy

Species richness

# number of different species per unit of Area

Species evenness

Relative abundance of different species per unit of Area

Things that affect species diversity

1. Latitude

2. Pollution = More pollution means lower diversity

3. NPP: High NPP means higher diversity

4. Habitat availability and condition: More habitat good condition and higher diversity

5. Time= more time higher diversity

Ecological succession

Change in species structure in a community over time

Primary Succession

Starts with bare rock and take centuries to develop soil. Lichens are the first to colonize. Ex: A new volcanic island or newly exposed glacial rock

Secondary Succession

Takes place in distributed areas and have pre-existing soil, takes significantly less time because seeds and nutrients are already present. Ex: An abandoned farm field or forest re-growing after a wildfire

Climax community

One in which populations remain stable and in balance with each other and their environment

Population Growth

Population change = (Births + immigrants ) - (Deaths + Emigrants) N= (B+I) - (D+E)

Biotic potential

Reproductive capacity of species able to have offspring

Intrinsic rate of increase

How much a species could grow with no limits

Environmental resistance

Factors which limit intrinsic rate of increase