SNAB succession, competition and energy transfer

very brief notes on succession, competition and energy transfer

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  • Created on: 12-10-15 16:42
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Tolerance- Is the ability to withstand fluctuations in biotic and abiotic environmental factors.
Biodiversity gives the ecosystem more tolerance.
Succession- orderly, natural changes that take place in an ecosystem over time
Primary succession Is the colonisation of new sites by communities
of organisms
Secondary succession Is the sequence of community changes that
occur when a community is disrupted by
natural disasters or human actions e.g.
Climax community The final stable plant community is the climax
community where the community reaches a
point of stability that can last for hundreds of
Deflected succession A community that remains stable only because
human activity prevents succession from
running its cause e.g. grazing prevents grass
from growing into woodland
Pioneer species: These are the first species to occupy a new habitat, starting new communities.
They have rapid reproductive strategies, enabling them to quickly occupy an uninhabited area.
Many have an asexual stage to their reproduction.
An example of primary succession forming an oak woodland:
1. Bare rock is colonised by mosses and lichen.
2. Small plants, ferns and grasses take over.
3. Larger plants with deeper roots appear.
4. Bushes and shrubs replace non-woody plants.
5. Fast growing trees form a dense, low wood.
6. Larger, slow growing oak trees create the oak woodland.
An example of secondary succession forming an oak woodland:
1. Bare soil is colonised by grasses and pioneer plants.
2. Grasses begin to predominate with time.
3. Shrubs replace the grasses.
4. Fast growing trees appear.
5. Slow growing oaks create the climax community.

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Competitionis often considered to be the most important biotic factor controlling population
Competition between organisms may be for a number of different factors, including food, light,
territory or reproductive partners.
Intraspecific competition:
This is competition for a resource between individuals from the same population. It causes the
population growth rate to slow down, and has a greater effect the less plentiful the resource is.
This form of competition can also be categorised as scrambleor contest.…read more

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Energy transfer
Only 1%-3% of the Sun's radiation (solar/ Light energy) reaches the plant
Over 90% of the Sun's energy is reflected back into space by clouds and dust, or is
absorbed by the atmosphere
Not all wavelengths of light can be absorbed and used for photosynthesis
Light may not fall on a chlorophyll molecule
A factor e.g.…read more

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Decomposers: These organisms form the end point of every food chain. They are bacteria or fungi
that obtain their energy by breaking down dead organisms from the other trophic levels.
Each description of a trophic level will describe an organism's role in the ecosystem. Organisms
may occupy more than one trophic level, (e.g. when acting as omnivores).…read more


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