Riassunto
Ecosystem is a dynamic entity composed of the biological community and the
abiotic environment. An ecosystem’s abiotic and biotic composition and structure is
determined by environmental factors (temperature, light intensity, species
population density,…)
In an ecosystem, biotic components are divided into:
PRODUCERS (plants, seaweed and some bacteria): they use solar energy to make
their nourishment;
CONSUMERS : they are divided into primary composers (herbivores) and
secondary composers (carnivores). They can’t make their nourishment so they live
on plants and other animals.
DECOMPOSERS ( bacteria and mushrooms): they live on tissue of dead organism.
Humans been very rarely refer to their ecological status and generally are not aware
of their impact on nature, but our daily lifestyle influences ecosystem very much.
But ecosystem is in danger: a lot of people, particularly farmers, use fossil fuels
which are highly polluting. Fossil fuels are those fuels that are deriver from the
processing of organic matter in a more stable and rich carbon. They are:
 Oil and its derivatives ( petrol, diesel, kerosene, …)
 Coal
 Natural gas
They are now the main energy sources because are easily transportable, they have
got a high ratio power/volume and they are relatively cheap. But they are also
highly polluting, result on an increase of CO2 in the atmosphere, they are not
renewable.
These feature, particularly the last, cause continues increase of their prices.
But we can use different alternative sources of energy: nuclear, hydroelectric, solar,
wind and geothermal.
Barrack Obama, for example, wants to save the world by curbing-carbon-dioxide
emission and discourage the use of high carbon fossil fuels. In fact, last year, the
House of Representatives voted to erect a “cap and trade” system, which would set a
ceiling on such emission and lower it each year.