Changing Ecosystems (PPT9) [U3/ T2] Flashcards
Define ecological succesion
The process by which communities in a particular area change over time.
Succession takes place as a result of complex interactions of biotic and abiotic factors.
Define sere
A sere is the term given to each successive community that forms as the ecosystem changes over time.
Define pioneer community
The first SEREmis the pioneer community
Define climax community
Each sere replaces the previous one until finally a stable community called the climax community is formed. This remains stable until recently disturbed.
What are the traits of R-selected species
- Mortality - density-independent
- Survivorship - higher mortality and early loss
- Competition - variable, often late, generalist niche
- Niche - generalist
- Selection favours - rapid development, higher rm, early reproduction, small body size, single reproduction (annual)
- Life span - short, usually less than 1 year
What are the traits of K-selected species
- Mortality - Density dependant
- Survivorship - late in life or consistent
- Competition - keen competition usually
- Niche - specialist
- Reproduction characteristics - slower development, larger body size, greater competitive ability, delayed reproduction, repeated reproduction
- Life span - longer —> one year
What are the traits of climax communities
- Structure - complex
- Niche - narrow
- Sp diversity - high
- Growth curve - S-shaped, reach carry capacity
- Species type - K
What are the two types of succession?
Primary
- Occurs when a barren area is colonised by organisms for the first time
Secondary
- Occurs in areas that have experienced disturbance which has removed vegetation
Define primary succession
Provide examples
Primary succession - bare rock - slower
- Colonization of a region where there is no pre-existing community
- Means bare and no soil
E.G.
- seagrass onto the empty seabed
- Newly emerged coral atolls, volcanic islands
- Newly formed glacial moraine
Define secondary succession
Provide examples
Secondary succession - soil - faster
- Occurs where an existing community has been cleared by a disturbance that DOES NOT involve complete soil loss
- The cycling of matter and flow of energy is interrupted as the components of the ecosystem are disturbed
- With soil present, recovery is faster, although this is conditional to species and climate
E.G.
- IDK
How to predict the mode of succession?
- The presence or absence of soil (primary or secondary)
- Consider the abiotic factors - soil nutrient ability
- Consider the biotic factors - resources utilization, types of species present (R or K), growth rates, biomass, biodiversity, the complexity of interactions (food web)
Fossils - Diatoms & Dinoflagellates
- Microscopic unicellular protists and an important component of phytoplankton
- Found in marine or freshwater ecosystems
- Fossilize well
- Temperature sensitive
- Provide past environmental data
Fossils - Pollen
- Very distinctive
- Can indicate types of plants growing in the vicinity
- Shows climate and ecosystem sustained
Fossils - Leaves and stomatal density
- Information about past environments
- CO2 levels and atmospheric temperatures
Fossils - Ice cores
- Gives evidence of past atmospheric conditions
- Trapped dust, ash, pollen, and gas provide clues to past volcanic eruptions, vegetation and atmospheric composition including methane and carbon dioxide.
