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ECOSYSTEMS AND ENVIRONMENTS UNDER THREAT
An ecosystem is a group of organisms which interact with each other and the surrounding environment so that matter is exchanged between the BIOTIC and ABIOTIC parts of the system.
These sytems can be as small as a puddle or as large as an ocean.
TERMINOLOGY
Abiotic = inorganic matter...soil, air, H2O
Biotic = organic matter (vegetation, animals)
Biomass = living matter (plants, bacteria, algae) - calculated as a total dry weight in a given unit area at a point in time (usually measured in kg/m2).
Gross Primary Productivity = the amount of new biomass created in a given area in 1 year, including that used for respiration, (measured in kg/m2/yr)
Net Primary Productivity = excludes that used for respiration
Respiration = the release of energy from Carbohydrates and fats which gives out carbon dioxide.
Closed system . .where energy not matter is exchanged across boundaries
Open system . . . where energy and matter are exchanged across boundaries
Positive and Negative Feedback change in one part of an ecosystem(+ or -) which brings about change in another part.
Autotrophs = organisms which create energy from inorganic matter (most are phototrophic i.e. they create energy from photosynthesis like green plants, blue-green algae and some bacteria, while other bacteria are chemotrphic i.e. they obtain their energy without using sunlight from inorganic matter like hydrogen sulphide.
Hetrotrophs = organisms which do not create energy but obtain it from the autotrophs These hetrotrphs include:-
Herbivores (plant eaters)
Carnivores (animal/meat eaters)
Omnivores (plant and meat eaters)
Detritivores (an animal that eat detritus or small fragments of dead and decaying matter)
Saprophytes (organisms which feed on dead animals and plants eg bacteria and fungi)
Decomposer (organisms which break down dead animal or plant matter to release nutrients- these are principally fungi and bacteria, but also woodlice and earthworms.)
Primary Producer = the first link in the grazing food chain.
Primary Consumer = an organism that feeds on a primary producer.
BIODIVERSITY
B iodiversity increases when an ecosystem is left undisturbed and allowed to reach it's climatic climax. However destruction or the continued alteration of habitats will lead to a decline in the biodiversity (number of species found in an ecosystem). This is a major problem for cold environments where the simplicity of the ecosystems will mean that they will be more affected by a loss of a species, than in the more complex equatorial systems.
There is also a knock on effect...taking out a plant like the bird's-foot trefoil through agriculture will mean that the common blue butterfly will be lost to that area.
Factors that produce a decline in Biodiversity=
increased use of chemicals, building development, road building , mining, wetland drainage,deforestation/afforestation,poor land management, conversion to agriculture.
ECOSYSTEMS ARE DYNAMIC SYSTEMS
What is an ecosystem?
biomes, habitat,food chain, food web, trophic level, trophic pyramid, open systems...inputs (solar radiation, gases, minerals from weathered rocks, precipitation gravity, soil nutrients,etc.) through puts and outputs (eroded soil, water, long wave radiation/heat, gases,etc.)...different scales from a tree to a rainforest
T hese components (above) which make up such a system and their inter-relationships (inter actions are the linkages that exist between one component and another, direct (climate) and indirect influences (length of growing season)
The structure of these ecosystems
= biotic components,(living matter) - plants, animals, decomposers and humans
= abiotic (non-living elements) - insolation,gravity, water, soil, gases, relief, rocks, temperature and wind
Autotrophs = producers
Hetrotrophs = consumers (herbivores,carnivores,omnivores, detritivores)
PRODUCTIVITY = gross primary productivity (the rate at which energy is produced by photosynthesis)
= net primary productivity (NPP) the rate at which energy is produced by palnts and made available to animals: GPP minus respiration ...increases towards equator and decreases towards the poles - factors influencing size of this = temperature, nutrient availability, vegetation type, vegetation health, moisture, competition, vegetation density ,human activity.
Biomass = amount of organic matter plant and animal, per unit area ..expressed as dry weight in gm-2 (also seen as the amount of stored energy, can be stated for each of the trophic levels or the system as a whole.
Nutrient cycling= macronutrients, micronutrients...3 main sources of nutrients ...rocks, atmosphere, dead organic matter.
Gershmels models - biomass, litter, soil... factos which influence stores and transfers = rainfall, thermal growing season, type of rock/type of weathering,surface runoff, soil erosion, leaching, rates of decay and decomposition by decomposers, nature and type of vegetation cover, vegetation density, fire, competition between plant species and age and health of plants, human activity.
You need to know all biomes generally but one GRASSLAND and one FOREST in great detail
THIS SHOULD INCLUDE DISTRIBUTION ,STRUCTURE, FUNCTIONING, HUMAN ACTIVITY
Remember spatial variations, temporal variations and a range of scales when answering a question on this area.
succession
plant community, pioneer community, climax community, mono-climax theory, poly-climax theory.
hydrosere, lithosere, psammosere, etc.
Climatic Climax = a plant community which is in equilibrium with its regional climate and soils, and in which all the ecological niches are filled and no further change takes place.
edaphic climax= soil determines community,
topographic climax= relief dominant,
biotic climax = grazing/trampling,
hydrologic climax= water,
plagio-climax = human intervention.
plant succession = a series of plant communities which progreesively, over time occupies a site.
primary succession = on bare ground that was previously unvegetated...bare rock, lava flows, sand, mud...the changes that take place mainly result from internal or autogenic factors, changes brought about by the plant community themselves..invasion, colonisation, competition, domination and decline, these often operated in sequence. First in are the pioneer species then secondary succession involving external or allogenic factors (fire, flood, human activity.Remember Arran succession, etc)
Plagio-climax communities...result from things like cutting down vegetation and putting in new plants, harvesting, grazing/trampling,burning (natural/man made) .
pioneers = the first plants to colonise an area of land. plants are usually small and must have low nutrient requirements. Many are annuals and legumes (meaning they can fix atmospheric nitrogen)