[19.6] succession Flashcards
what is succession?
a long term process whereby plant communities in an ecosystem are gradually replaced by a series of changes
what happens in each stage of succession?
new species colonise the area and these may change the environment
how might a species change its environment during succession?
- make it less suitable for existing species. new species may out-compete the existing one so take over a given area
- more suitable for other species with different adaptations. this species may be out-competed by the better adapted new species
what adaptations do typical pioneer species have that allow it to establish quickly?
- large quantities of wind-dispersed seeds / spores
- rapid germination of seeds
- fast reproduction rate
what adaptations do typical pioneer species have that allow it to be self-sufficient?
- photosynthetic
- nitrogen-fixing from atmosphere
- tolerance to extreme conditions and harsh abiotic factors so it can survive where other species cannot
what is a sere?
what each stage of succession is known as
1st stage of succession
- low number of species and individuals
- pioneer species colonise an inhospitable environment (eg. algae, lichen, mosses)
- adapted to surve harsh abiotic factors
2nd stage of succession
- environmental conditions alter due to presence of pioneer species
- environment becomes less hostile eg. shelter for germination, new habitats for animals
3rd stage of succession
- pioneer species are outcompeted by newcomers
- new community further changes conditions, until they are in turn outcompeted
- eveutally climax commnity is reached
- balance of species stablises
- gradual blending of one community into the next
what is a climax community
a community of animals and plants with much biodiversity and few species replacing those established, which stays stable over a long period of time
what common features emerge during succession? (8)
- harshness of abiotic conditions ⭣
- soil factors (eg. depth, stability, water content) ⭡
- number and variety of habitats and niches ⭡
- species richness ⭡
- biodiversity ⭡ then ⭣
- complexity of food webs ⭡
- total ecosystem biomass ⭡
- overall ecosystem stability ⭡
what is secondary succession?
- when land has already been sustained or life is suddenly altered so an ecosystem returns to its climax community in the same way but more rapidly
- some of the species in the climax community may be different
why is secondary succession quicker than primary succession?
- seeds often remain alive in soil
- influx of animals and plants through dispersal and migration from the surrounding area
what impact can humans have on factors can interrupt succession and prevent the development of a climax community or destroy an established climax community? (7)
- grazing
- agriculture
- ploughing
- deforestation
- pollution
- climate change
- management for conservation
what impact can natural events have on factors can interrupt succession and prevent the development of a climax community or destroy an established climax community? (4)
- flood
- fire
- drought
- disease
