THE ECOSYSTEM: A COMPLEX SYSTEM
The ecosystem is a complex system consisting of organisms living in a certain environment. Animals and plants are components of biotic ecosystem, wherease the subsoil, air and water, light, temperature, climate, rainfall, etc.. are part of the abiotic components. The components of biotic and abiotic found between them a set of relationships that characterize the ecosystem itself and led it into a balance  temporary.
According to their function within an ecosystem, the components of biotic (beige), can be divided into:

• Producers (plants, algae and some bacteria) are the bodies "autotrophic" which produce from the organic substance to live and grow, using simple inorganic molecules such as water, carbon dioxide (CO2) and nitrates.
• Consumers are organisms "heterotrophic" because they are unable to produce their own food, and eat and then the producer (eg consumers herbivores like cows and sheep, which eat the grass of the meadows) or other consumers (consumers carnivores like the lion or the man himself)
• Decomposers: are mushrooms and bacteria that feed on decomposing tissues of dead organisms.

Each ecosystem contains a defined amount of organic matter that includes all its plant and animal organisms, the term of biomass, it identifies the weight of the substance, calculated on the dry and per unit of area occupied by the ecosystem itself.

 

ENERGY TRANSFER IN THE ECOSYSTEM
Relations between the different components of an ecosystem are so narrow that if one of them is damaged, the entire ecosystem is perturbed. The main relations are those formed by flows of energy and nutrient flows. The ecosystem is an open system than the energy, energy goes in and out continuously from the system. Energy enters in to the ecosystem primarily by the sun crosses the biotic community and its food web, and comes out as heat, organic matter and organisms produced. More specifically, the bodies producers are able to capture and use the sun's energy to transform some inorganic compounds into organic compounds through the process of photosynthesis. These compounds are used by the producers themselves in two ways: to live and grow (in this case the organic compounds are to form new structural elements of plants like leaves and new branches). Herbivores, eating plants, they take and metabolize organic matter, ie transformed into other organic materials suitable for use in all vital functions (breathing, movement, body heat and others) and as a structural material for their growth. Similarly, behave carnivorous animals, feeding on other animals. The process continues from one category of organisms to another . The transfer of energy through the food web, however, is accompanied by leak as heat dissipated into the environment to the second law of thermodynamics . This means that in the diet of carnivores will be available less energy than is available to herbivores, which in turn receive from their food less energy than is used by plants in the metabolism of the food itself, (the organic matter formed through the process of photosynthesis). The transfer percentage of energy from one trophic level to the next is called "eco-efficiency or effectiveness of the food web".

TROPHIC CHAIN
There are two types of food webs: the web of grazing and the web of debris. The first part of green plants, through herbivores grazing, then the top-level carnivores that eat herbivores, then to the second level carnivores that eat other carnivores. The second part instead of dead organic matter, passes through the micro-organisms from these animals detritivores (consumers of detritus), and ending their predators, ie carnivores. Food webs are densely interconnected, and that is why we talk about food web (or food). In natural ecosystems, organisms that obtain food from the sun with the same number of passes in the same trophic level. Then, the green plants (producers) occupy the first trophic level, organisms that feed on plants occupy the second level (primary consumers), carnivores belong to the third level to fourth level predators and carnivores (secondary consumers and tertiary). The source and quality of energy available indicate, for all levels, the type and number of organisms, and their development processes.

NUTRIENTS
Unlike energy, which goes in and out from the ecosystem along a linear path, the field follows a circular route going from non-living compartment to living organisms and back to the abiotic compartment. These ways are defined biogeochemical cycles. Carbon, hydrogen, nitrogen, phosphorus and calcium are needed by living organisms in large quantities and this is called macronutrients. Other elements such as iron, magnesium, manganese, zinc, etc.. Are required in lesser quantities and are defined for this micronutrient. This division is purely academic, as the organizations grow and reproduce they need all these substances in varying degrees depending on the time of their physiological development. Substances that can be defined as essential will vary from species to species. Both the numerical development of a population, both the individual growth of the organism depend on that element or compound that, given the needs of the organism, is found in lesser quantities in the environment: the limiting factor.

PRIMARY PRODUCTIVITY
The primary productivity of an ecosystem is defined as the rate at which solar energy is converted by photosynthesis into organic matter.
Then:

• Gross primary productivity (PPL), the total rate of photosynthesis (thus also called photosynthesis total)
• net primary productivity (PPN), the rate of storage of organic matter produced, net of the one used by the plant to live (so that even apparent photosynthesis)
• net productivity of the community (PNC) is the rate of storage of organic matter not used by herbivores and carnivores
• productivity secondary (PS) is the rate of storage of organic matter for energy purposes by consumers (ie, heterotrophic organisms, unable to carry out photosynthesis).

A high rate of primary productivity in ecosystems is achieved when physical factors (eg: water, nutrients and climate) are favorable. The presence of secondary forms of energy can help to raise the rate of primary productivity. One example is that of estuaries, one of the most productive ecosystems in the world. In estuaries, fresh water mixes with the seawater. The plants here are extensive photosynthetic mat. Stems and roots trap large amounts of food particles, and completed their life cycle, providing additional share decompose organic matter to the ecosystem. The secondary energy is represented here by the action of tides, which helps on the one hand, the rapid movement of nutrients and, helps remove waste products, so the organisms that live here (larvae of sea bass, sea bream , mullet and clams) did not spend energy to get food or to eliminate waste and can grow more quickly.

 

ALTERATION OF THE FOOD CHAIN
Technological innovations applied to 'agriculture to combat the pest organisms that damage crops has led to the use of pesticides in large quantities and for a long time. These substances are toxic and their accumulation has changed the balance of the biosphere because they have harmful effects on many organisms including man. DDT is a substance which, introduced into the environment, has caused damage to ecosystems, creating a phenomenon of widespread pesticide contamination on a global scale. Studies have found that the amount of DDT present in organisms have confirmed its presence in fish from around the world, in the Inuit, in animals living in polar regions and in breast milk. This passage through the various levels of DDT in the food chain is possible because the molecule remains unchanged, it does not degrade easily. It follows that at each jump of level (from the plant the insect, insectivorous bird, the mammal predator), the concentration of DDT in organisms increases by about 10 times. That is, if the mass of bodies became the tenth part, the concentration of the pesticide becomes ten times higher.
The damage done to the bodies by DDT are alarming: when the molecule reaches the sea, it slows down the photosynthetic activity of algae, birds' eggs are fragile and break easily during the hatching because they are poor in calcium, decreases the number of individuals population, humans relate to damage organs and systems.

AN EXAMPLE OF  ALTERETED ECOSYSTEM
In Borneo, the use of DDT has caused the deterioration of the ecosystem, indirectly affected the man. The widespread use of DDT to kill mosquitoes that transmit malaria has killed all insects, including useful to humans as cockroaches. These insects are the main food of lizards, whose population has fallen greatly as the number of cats that ate the lizards. The cats, however, kept under control the population of mice: reduction of cats has led to an increase in the number of rats in overcrowded conditions that transmit dangerous diseases to humans.
Borneo, after DDT spraying campaigns, was hit by infectious diseases that have caused more victims of malaria.

THE ECOSYSTEM IS IMPORTANT FOR HUMANS
Terrestrial and aquatic ecosystems are "factories" natural complex and perfectly organized that produce all that is necessary to enable life on Earth and to cover basic human needs: food, fiber, water. Some of these functions of ecosystems are essential for humans, such as air and water purification, climate control, the cycle of nutrients, soil fertility. In addition, some ecosystems (beaches, forests, lakes, high mountains, isolated valleys) are the ideal places for recreation and tourism. In addition, it also recognized the importance in economic terms: 50% of the inhabitants of the world finds employment in agriculture, forestry and fisheries. This percentage rises to 70% when considering only the sub Saharan countries, Asia and the Pacific. 25% of the countries of the world has an economy that still depends almost entirely from the areas mentioned above. Only agriculture produces 1.3 trillion dollars in food and fiber every year.

THE BIOME
A forest, a lake, a river, a meadow, a beach, the sea, even the green spaces of the city are all ecosystems. In short, every inch of our planet is, or is part of an ecosystem. Ecosystems can have very different sizes. Ecosystems are considered to be the temperate forest, which occupies most of North America, Europe and northern Asia, and the cavity filled with water and life of a beech forest that is part of the same (in this case is called microecosistema ").
The Earth itself can be considered one large ecosystem. The division into smaller ecosystems and defined is necessary in the case of targeted studies, but in fact the limits of an ecosystem normally blend into those of another, and most of the bodies may belong to different ecosystems at different times. For example, fresh water becomes brackish near the coast, and in this way the ecosystem of the sea and fresh water are linked by flows of energy and food. The boundaries of an ecosystem can also vary over time due to various factors that alter the balance, including the extinction of a species, human intervention, the introduction of exotic species in an ecosystem and others. Under ideal conditions, areas that have uniform physical and chemical characteristics should have ecosystems that are well defined and easily recognizable. In nature, however, is not possible to find conditions so uniform. Especially in the case of terrestrial ecosystems, it is easier to identify groups of ecosystems. In particular, neighbors that share ecosystems and biogeochemical cycles have similar abiotic components are called "biomes". Terrestrial ecosystems can thus be grouped in several biomes

THE ECOSYSTEM OF EARTH
Based on the type of vegetation that characterizes them most, ecosystems are recognizable, and are divided into:

• Deserts
• savannah
• steppe
• temperate forests
• tropical
• boreal forest (taiga)
• tundra
• Mediterranean

Aquatic ecosystems are divided in hand:

• freshwater ecosystems: lakes and ponds, rivers and streams, swamps and marshes
• marine ecosystems: coral reefs, oceans, continental shelves, areas of slope of nutrients, estuaries. (See chart)

On Earth, however, there are not only natural ecosystems, but also those created artificially by humans at the same time that development has led him to organize his social life and way of living and produce according to specific characteristics.
The artificial ecosystems are divided into:

• Urban-industrial ecosystems (metropolis)
• ecosystems rural (small towns)

• agroecosystems (cultivated field).

 

A CHANGING WORLD: THE ECOLOGICAL SUCCESSION
The story of an ecosystem, from birth to maturity, is called ecological succession. The ecological succession, in practice, is a continuous sequence of changes in biotic and abiotic components of an area, so we come to a stable ecosystem (what is called a "climax") characterized by a balance between its various components, namely no prevail decreed the extinction. The sequence of communities that gradually replace the ecosystem is known as "serious" and are called "serial stages" the different stages of transition. In some cases, the people themselves alter the environment in which they live and cause their own extinction for the benefit of other species of organisms. Examples of this evolutionary process can easily be found in nature, where the formation of any new environment (due to fire in a forest, diversion of a watercourse, to an abandoned agricultural field, etc..) Initially determines the spread of organisms as "pioneers," meaning they are able to grow despite the difficult conditions of the area (low presence of nutrients). The vital activity of these early organisms change the environment, creating new conditions that are favorable for other organisms more demanding. These are developed often causing the elimination of the entities pioneers.
To understand this better
For example, mosses, lichens and grasses are often pioneer species on or solidified lava bedrock. These bodies are able to shatter the bedrock to extract the minerals necessary for their survival. Furthermore, once dead, they provide that the organic material that decomposes, becomes "soil" used by plants and are setting up at a later time to feed and grow. An example of ecological succession is what happens on the sand dunes: the first plant species and are setting up are very adaptable and able to use the modest availability of nutrients. These first pioneer species establish, with their root system, making the sand dunes are more stable. Moreover, after death, remain on the ground and enrich organic matter resulting from their decomposition. This creates an environment richer and therefore more suitable for sustaining life of organizations demanding that gradually supplant those pioneers, and the species composition becomes increasingly diversified and is set in natural processes of power and competition becoming more complex.

AN ARTIFICIAL ECOSYSTEM: AGRO-ECOSYSTEM
A typical example of artificial ecosystem is the cultivated field, or agro-ecosystem. This is a natural system modified by humans through agricultural activity. It differs from the ecosystem natural for four aspects:

• simplification: the farmer prefers a type of plant fighting all those animal and plant species that could damage
• the input of energy by humans in the form of machinery, fertilizers, pesticides, selected seeds, work
• biomass (harvest) is removed once mature. This makes an open ecosystem, ie dependence on nutrient re likely to fuel a new process of birth and development of organic material (plants). A natural ecosystem, however, the biomass remaining in the original manure alone.
• the release of pollutants which, in the case of intensive farming, chemical fertilizers, pesticides and other chemicals that accumulate in the ecosystem is not biodegradable or are lost in the underground, and in some cases to seriously pollute groundwater, rivers and seas .

The house is a small artificial ecosystem. Come from outside objects, food, solar energy, water, etc.. and are placed outside the solid and liquid waste generated by human activities. Similarly the city. It depends on outside supplies of water, food, construction materials and other resources necessary for its development and always outside discharge their waste (in landfills and incinerators), ie everything that does not contribute to the survival of the ecosystem city.

 

 

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