| Succession | - The gradual directional change of a community over time |
| Two types of succesion | - Primary succession
- Secondary succession
(end of both is climax community) |
| Primary succession | - Starting point is bare ground |
| Secondary succession | - Here a community is damaged and the soil is left plants to colonise (e.g. a woodland has been felled) |
| Pioneer species | - A highly adapted species that is the first to colonise e.g. algae/lichens |
| Climax community | - Stable community - final stage of succession
- The community is still determined by abiotic factors |
| Abiotic conditions that affect primary colonisers | Climate: temp, rain and sunlight, can affect the survival and growth of primary colonisers
Light: affects the ability to photosynthesise
Wind: intensity and direction of wind as it can affect the distribution of seeds and pollen |
| How marram grass is adapted to the harsh abiotic conditions | Root system: deep root system that can reach down to the underlying groundwater, allowing it to access water even in dry conditions
Leaf structure: narrow and stiff, reducing water loss through transpiration
Wind resistance: strong stems and leaves that can withstand high winds |
| How marram grass or any other species colonisation changes the abiotic conditions | Soil moisture: stabilise the sand dunes by binding the sand particles together with its roots. This increases the soil moisture, as the sand is less likely to be blown away and water is better retained in the soil.
Microclimate: They can also modify the microclimate of the sand dune ecosystem, creating a cooler and more humid environment that is better suited to the growth of other plants. |
| Explain how succession leads to a climax community (1) | - Succession either occurs in areas with no prior vegetation e.g. on sand dunes, or in areas where a community has been disrupted e.g. after a fire or a flood. |
| Explain how succession leads to a climax community (2) | - This creates an abiotic environment that is hostile so only highly adapted species are able to colonise - pioneer species |
| Explain how succession leads to a climax community (3) | - In the pioneer community the species diversity is low as there are few niches, they will compete, some will die and decomposes and release nutrients and produce ‘soil’. |
| Explain how succession leads to a climax community (4) | - This allows new species e.g. grasses to colonise, the grasses then outcompete the pioneer species, increasing diversity. |
| Explain how succession leads to a climax community (5) | - The abiotic conditions have changed due to the biotic environment, this process continues over many years until there is climax community where the diversity is high, there are lots of niches, the abiotic conditions are stable. |
