SNAB topic 5: ecosystems

notes on the ecosystem section topic 5

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  • Created on: 28-09-15 16:31
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HABITATS
Habitat - a place with a distinct set of conditions where an organism lives within an ecosystem. Within a
habitat there may be many microhabitats e.g. icy wastes of the Arctic contain many different habitats
COMMUNITIES
Population- a group of the same individuals of the same species found in an area
Community- the various populations sharing a habitat or an ecosystem
If two species live in the same habitat and share the same niche= they will compete with each other
until the better adapted of the two species out-competes the other and exclude it from the habitat.
WHAT DETERMINES WHICH SPECIES OCCUR IN A HABITAT?
A particular species lives in a particular habitat because it is adapted, able to survive and reproduce
there. The conditions in which species compete for survival are defined by the abiotic and biotic
factors.
ABIOTIC FACTORS
Are the non-living or physical factors such as: Solar energy input (affected by latitude, season, cloud
cover), climate (e.g. rainfall), oxygen availability (important for aquatic systems), edaphic (related to
soil= pH, and mineral salt availability), pollution (can be of air, water or land) and catastrophes (e.g.
earthquakes, floods, fires and volcanic eruptions)
BIOTIC FACTORS
Are `living' factors such as competition (for resources and can be interspecific (between species)
or intraspecific (within species)), grazing, predation and parasitism (relationships between to
organisms where one benefits the other's expense), mutualism (is a relationship where both
partners benefit)
Biotic factors are usually density dependent where the effects are related to the population size
relative to the area available. The larger the population density= the greater the competition for
food, space etc.
ANTHROPOGENIC FACTORS
are those that arise from human activityand can be either abiotic or biotic.
Grazing = introduction of sheep and rabbits and the removal of predators of grazing animals are
the result of human activity. Grazing by domesticated animals is accompanied by high stocking
densities, fencing, the introduction of cultivated types of grass and the use of fertilisers= this
means that the environment is no longer `natural'
What could happen if grazing sheep in grassland are removed?- A climax community may
form where the grassland develops into a woodland. The succession may result in the loss
or change in biodiversity
ADAPTED FOR SURVIVAL
Species survive in a habitat because they have adaptations that enable them to cope with the
biotic and abiotic conditions of their niche.
ECOSYSTEMS ARE DYNAMIC
A community which changes over time is known as a succession.

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PRIMARY SUCCESSION
A primary succession starts in newly formed habitats where there has never been a community
before. Unless prevented, succession then continues until a relatively stable community is
established.
The pioneer phase: enter the botanic mavericks = a pioneer species are the first to colonise bare
rock such as lichens and algae. They are the only species which can cope with the extreme
temperatures and lack of soil, water and nutrients.…read more

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