Biosphere: Part of earth inhabited by living organisms
Abiotic factors: Physical/ Chemical factors
Biotic factors: Living e.g. predation & competition
Population: Group of individuals of the same species found in an area
Community: Various populations sharing a habitat
Solar energy input: Affected by latitude, season, cloud cover.
Light essetial for photosynthesis, initiating germination & in many animals, light controls behaviour
Climate: Includes rainfall, wind exposure, and temperature
Topography: Includes altitutde, slope, aspect & drainage
Oxgen availability: Fast flowing streams are better oxygenated than stagnant pools
Edaphic factors: Soil, pH, soil texture
Pollution: Of air, water or land
Catastrophes: Infrequent events that disturb conditions
Competition: For resources like food, light, water, space
Grazing, predation & parasitism: Relaionships between 2 organisms, 1 benefits at other's expense
Mutualism: Relationship where both partners benefit
= Newly formed habitats, where there has never been a community before.
1. Pioneer species lichens & algae, first to colonise bare rock. Can cope with extreme conditions.
2. Pioneers breeak up rock surface= organic matter accumulate. Chanage conditions in habitat to make more suitable for other species.
3. Wind Blown moss spores start growing.
4. Mosses build up more organic matter= soil: can hold water.
5. Development of soil enables seeds of small, shallow rooted plants to establish.
6. Conditions in habitat improve, seeds from larger, taller plants appear.
7. Plants out compete existing community.
8. Eventually a stable climax community is reached, usually dominated by trees.
Secondary & deflected succession
Secondary succession= on bare soil where an existing community has been cleared.
In absence of human interference, secondary succession would lead to re-establishment of a climax community.
Bare Soil does not stay bare for long. Seeds of many other species will already be lying dormant in the soil, others brought by wind/ animals.
Groundsel is an example of a pioneer species adapted to take advantage of bare soil with little competition.
- Seeds widely dispersed by wind
- Rapid Growth
- Short life cycle
- Abundant seed production
Deflected succession= community that remains stable because human activity prevents succession from running its course.
Grazing, mowing/ burning may be used to deflect succession.