Succession Flashcards
Define succession.
The change in community structure and species over time. New species invade and replace existing ones until a climax (stable community) establishes itself.
Define primary succession.
The sequence of changes when species are introduced to an area not previously supported by a community
Define a sere; xerosere; seral stage
Sere = sequence of communities
Seral stage = stages of a sere
Xerosere = a sere in a dry environment
What were the 8 stages of the ice age undergoing xerosere succession to mixed deciduous forest.
- Pioneer species (algae and lichen)
- Soil formation
- Wind blown spores - mosses
- Developed soil=herbaceous plants
- Tall grasses - shade tolerant species
- Soil thicker as plants + animals die
- Shrubs + small trees grow
- Large trees outcompete
How did soil form after the ice age?
- Weathering of rock
- Erosion by lichens
- Accumulation of decomposing organic material
What is the climax community balanced with? (4)
- GPP and total respiration
- Energy absorbed and released
- Nutrients uptake and released back
- New growth and decomposition
What is secondary succession?
The recolonisation of a habitat previously occupied by a community but disturbed by for example fire. It is much faster.
What is disclimax?
A stable community maintained by human activity.
How can human interference effect succession? (3)
- Grazing by sheep and cattle prevents shrubs growing
- Farming of land excludes species not intentionally introduced
- Deforestation removes trees.
What are the 3 factors affecting succession?
- Migration of spores seeds and animals
- Competition
- Facilitation
What is interspecific and intraspecific competition?
Interspecific = different species Intraspecific = same species
What is the competitive exclusion theory?
Gause cultured 2 species of yeast. On their own, they followed a regular one step curve. In the same condition, the faster one outcompeted the slower one, showing that two species can’t occupy the same niche.
Define mutualism and give an example.
When a symbiotic relationship is beneficial to both. E.g. Flowering plants and pollinators or birds eating insects off a deer.
Define commensalism and give an example.
One benefits and one is unaffected. E.g. A squirrel on a tree is protected and sheltered but the tree is unaffected.
Give an example of how a symbiotic relationship can change.
Bacteria in mammalian guts can provide vitamin K, but they can get it from their diet so it is commensal. However if their diet becomes lacking in vitamin K and they get a deficiency it comes mutualistic.
