Thursday, December 17, 2009

Ecosystem : structure and attributes

Ecosystem is the basic structural and functional unit of ecology. Ecosystems are made up of abiotic (non-living) and biotic (living) components in a specified volume of space. Ecosystems are open to the flow of energy and materials. Through the process of photosynthesis, green plants capture sunlight energy and combine it with carbon dioxide and water to produce carbohydrates and oxygen. Animals feed on plant biomass and transfer  energy through the ecosystem. The decomposers break down dead organic matter of plants and animals and restore their chemical components to the soil. Ecosystems provide many products and services that are crucial to human survival. Ecosystem concept provides a convenient means of understanding the highly complex global ecosystem.

Main attributes of Ecosystem

·         Structure – Composed of biotic and abiotic sub-components
·         Function – Energy exchange between living community and physical environment
·         Complexity – High levels of Biological integration
·         Interaction and inter dependency – Change in one effects another
·         Temporal – Change overtime - Dynamic

Ecosystem structure (Components)

All ecosystems are made up of abiotic and biotic components.
Abiotic (Physical) Components
      The non – living elements such as sunlight, water , air and soil are called abiotic components. These components are classified into 3 types:  Climatic factors (atmospheric temperature , wind , sunlight  and humidity) , edaphic factors (soil types, organic matter , mineral composition and inorganic and organic substances ( carbon, nitrogen , oxygen , proteins, carbohydrates , lipids , humus).

Biotic components
 Living organisms are called biotic factors. It includes three kinds of organisms such as primary producers, consumes and decomposers.
1. Primary producers – Green plants make use of sunlight and other abiotic elements to produce nutrients. Plants are also called autotrophic organisms because they manufacture their own food from simple inorganic substances.
2. Consumers – They feed on autotrophs (plant) or other heterotrophs to obtain energy. The primary consumers such as herbivores feed on the plants. The secondary consumers such as carnivores feed on herbivores. Scavengers such as bacteria feed on the dead and decaying organisms.
3. Decomposers - Decomposers are reducer organisms such as bacteria or fungi. They break down dead bodies of plants and animals into simpler compounds and return inorganic nutrients to the soil environment.

Properties of Ecological Systems

  1. Networks –Interdependence, diversity, complexity
  2. Boundaries- Scale and limits
  3. Cycles – Recycling of resources and partnership
  4. Flow –through – Energy and resources
  5. Development – Succession and  co-evolution
  6. Dynamic balance- Self – organization, flexibility, stability, sustainability

Characteristic features of ecosystems

An ecosystem is a functional unit of nature consisting of abiotic and biotic components. Ecosystem varies greatly in size from a small pond to a large rain forest. Ecosystems exist as different varieties. Forest, grass land and desert are few examples of terrestrial ecosystems. Ponds, lakes wetlands, rivers and estuaries are some examples of aquatic ecosystems. Crop fields and aquarium are a few examples of man-made ecosystems.
Each ecosystem has characteristic physical structure resulting from the interaction of abiotic and biotic components. Species composition and stratification are the two main structural features of an ecosystem. A constant input of solar energy is the basic requirement for any ecosystem to function and sustain.
Biological productivity – primary production is the rate of capture of solar energy or biomass production by plant producers. Secondary production is the rate of assimilation of food energy by the consumers.
Food chains are the pathways along which nutrients pass through an ecosystem. Energy is passed through an ecosystem  via food chains and food webs. A food chain is a straight line sequence of who eats whom. A food web is a series of interlocking food chains.
10 per cent law – Only 10 per cent of energy is transferred from one trophic level to another. This flow of energy is unidirectional. During this energy transformation, some energy is lost as waste heat.
The biogeochemical cycle is the circulation of a chemical element (e.g. carbon, nitrogen and oxygen) between abiotic and biotic compartments of the ecosystem.  Chemical cycles help in the balance of organic and inorganic substances in the ecosystem.
A trophic level is a group of organisms that get their energy from the same source (trophic = feeding).Green plants get their energy from the sun through photosynthesis. Therefore they are all in the same trophic level. There are 3 basic trophic level groupings. i.e. producers, consumers and decomposers.
In most ecosystems the pyramids of energy, number and biomass are upright. i.e. producers are more in number and biomass than the herbivores and herbivores are more in number and biomass than the carnivores.
The composition and structure of a biotic community   undergoes change in response with the passage of time. These changes constitute ecological succession. Succession begins with the invasion of a lifeless area by pioneers followed by successors and finally a stable climax community is formed.
Healthy ecosystems are the base for a wide range of benefits to humanity known as ‘ecosystem goods and services’. The proper functioning of the world’s ecosystem is critical to human survival.

Ecosystem functions

“Ecosystem function is the capacity of natural processes and components to provide goods and services that may satisfy human needs either directly or indirectly.”

 Primary functions of ecosystem 

·         Regulatory functions – govern climate,  rain fall and life support systems.
·         Habitat functions – provide habitat for wild plants and animals.
·         Production functions – supply food, fuel, fibres and fodder.
·         Information services – cover the beauty, inspiration and recreation that contribute to our spiritual welfare.
Ecosystems purify the air and water, generate oxygen and stabilize out climate.
Ecosystems have thousands of plant, animal and microorganism species which are used and traded by humans for food, shelter, medicinal, cultural, and aesthetic and many other purposes.
Ecosystems provide refuge and reproduction habitat to wild plants and animals.
The microorganisms decompose and detoxify organic matter derived from plants and animals of both aquatic and terrestrial ecosystems.

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