[IB Biology: Ecological Notes] -------- [Review of Succession]
Ecological Succession

Succession: Gradual change in species occupying an area. Due to changes in 1 or more abiotic or biotic factors favoring some species over another.

Primary Succession: Gradual establishment of an ecosystem where one did not exist before (Ex: on bare rock). Examples:

Primary Succession on a Sand Bar

Primary Succession on a Rock

Secondary Succession: Gradual reestablishment of an ecosystem from an area where it previously existed. Examples:

Pioneer species: Plant or animal species that are the first to occupy a newly exposed or disturbed area. Examples:

Climax species: Last stage of succession. One in which populations of all organisms are in balance w/ each other & existing abiotic factors.

Examples: Old Growth Forest

Factors Affecting the Distribution of :
Animal Species
Plant Species
a) Temperature a) Temperature
b) Water b) Quantity of Light
c) Food Supply c) Water
d) Breeding & Nesting Sites d) soil pH
e) Territory e) Minerals (includes salts)
Changes Which Occur During Succession
Soil Structure:

Early Successional Stages

(Pioneer Plants)

Late Successional Stages

(Climax Community)

Soil Depth
None or Shallow
Deeper
Organic Nutrients
Few
Numerous
Moisture Retention
Poor
Good
Ability to Recycle Nutrients

Poor

(few saprotrophs)

Good

(many saprotrophs)

     
Ecosystem Structure:    
Plant Size
Small
Large, or a mix from small to large.
Species Diversity
Low: few species
High: many species
Trophic Structure
Mostly producers, a few decomposers .
Many producers, herbivores, carnivores & decomposers.
Ecological Niches
Few
Many
# of Food Web Links
Few
Many: Complex connections between food chains.

Competitive Exclusion Principle: When 2 species compete very directly for resources, one eventually excludes the other from the area.

Biodiversity: In the natural world, all living species, ecosystems, and genetic diversity within the species. Known Species: 1.75 million plants, animals & microbes. Estimated totals: 4-112 million unidentified species.

Extinction: Death of all members of a species. All the genes of the species are lost forever.

Recent Examples & Causes of Extinction:

[Review of Succession]
Slichter