Wednesday, September 18, 2013

Important questions-i

Write in detail about structure and function of an ecosystem.
Ecology is the study of ecosystems and ecosystem is the basic functional unit of ecology. A group of
organisms interacting amongst themselves and with the environment is called ecosystem. An ecosystem
is a community of different species interacting with each other and their non-living environment
thereby exchanging energy and matter.
Structure of an ecosystem shows the relationship between abiotic and biotic components.
All the living members of an ecosystem form the biotic community. Ex: Plants (producers), animals
(consumers) and microorganisms (decomposers).
The non-living components (physical and chemical) of an ecosystem collectively form the abiotic
community. Ex: Climate, Soil, Energy, Nutrients, Water and Air.
Physical components are necessary for the growth and maintenance of living components of the
Chemical components are the source for essential nutrients. They consist of organic substances
(protein, lipids, carbohydrate) and inorganic substances (Al, Co, Zn, Cu-micro elements C, H, O, P, N,
P, K-macro elements)
Function of an ecosystem is of three types:
Primary function: The primary function of all ecosystems is to manufacture starch (photosynthesis)
Secondary function: The secondary function of all ecosystems is to distribute energy to all the
consumers in the form of food.
Tertiary function: All living organisms die and these dead systems are decomposed to initiate the
third system of ecosystems called “cycling”.

Define and differentiate between food chain and food web with a diagram
A food chain is a model that shows the flow of energy from autotrophs to a series of organisms in an
environment. The energy that flows can be different for each food chain. The food chain describes the
flow of food from one organism to the next thereby giving energy to the organism digesting the food.
The number of steps involved in a food chain is restricted to four or five. The energy available
decreases with each step. The energy loss takes place in the form of heat. The three types of food
chains are:
Grazing food chain,
Detritus food chain and
Parasitic food chain.
All food chains start with the sun.
The interlocking pattern of various food chains in an ecosystem is known as food web. In a food web
many food chains are interconnected. In a food web different types of organisms are connected at
different tropic levels resulting in several opportunities of eating and being eaten at each tropic level.
An important difference between food chain and food web is that food chain is linear and this implies
that if one species becomes extinct, the species in the subsequent tropic levels are also affected.
However, in a food web, if one species is affected, there is no serious effect on other tropic levels as
there are several options available at each tropic level.
Enumerate the value of biodiversity
The value of biodiversity is classified into:
Direct values and
Indirect Values
Direct value of biodiversity: Biodiversity has direct value in the form of consumption in agriculture,
medicine and industry. Among all plant species identified as fit for human consumption, only 150 have
been cultivated on a large scale. Two types of direct values are:
Consumptive use value and
Productive use value
Consumptive use value is the value placed on nature's products that are consumed directly without
passing through a market. Consumptive use value is not included in national income accounts.
Consumptive use value benefits the communities closest to the resource if harvested sustainably with
proper management. Product examples of consumptive use value are firewood, food and game meat.
Productive use value refers to products that are commercially harvested and sold in a market. Its value
is estimated at production end after addition of cost and value. The productive use value has a major
impact on national economy. Product examples of productive use value are timber, fish, honey,
mushrooms, game meat sold in markets and medicinal plants.
Biodiversity has indirect value since it provides economic benefits without being harvested. Direct
value of biodiversity is derived from its indirect value. Indirect value of biodiversity is listed below:
Non consumptive use value
Option value
Existence value and
Information value
Non consumptive use value refers to nature's functions and services. Examples of this are
photosynthesis by plants that provides support system for other species, maintenance of water cycle,
regulating climate, production and protection of soil, absorption and breakdown of pollutants,
recreational, aesthetic, socio-cultural, scientific, educational, spiritual and historic values of natural
Option value refers to the indirect value of a species potential to produce economic benefits to the
society in the future.
Existence value is the value gained from continuous knowledge of existence. An example in this
context is the expense incurred by the administration of various countries to develop techniques in
order to prevent a species from becoming extinct (Giant Panda, Blue whale, White tiger, etc).
Information value refers to the educational, scientific, aesthetic and tourism values of biodiversity in an

What are the types of biodiversity conservation
With the rapid increase of human population and resulting expansion of man's needs coupled with
scientific knowledge led to over-exploitation of natural resources. Eventually, conservation of
biological diversity became a global concern. This involves influencing behaviour of people at local
level through education, at the national level through policy work and awareness programs.
International corporations should ensure that their business do not contribute to further loss of
The two main types of biodiversity conservation are:
In-situ conservation and
Ex-situ conservation
In-situ conservation is defined as the conservation of genetic resources through their maintenance
within natural or man-made ecosystems in which they occur.
In-situ conservation effort is setting-up of protection areas. This technique is the best conservation
strategy. However, its implementation is sometimes unfeasible. National Parks, Sanctuaries and
Biosphere reserves are some types of in-situ conservation.
Ex-situ conservation is defined as conservation made outside the habitat of an ecosystem. In case the
habitat of rare or endangered species is destroyed, ex-situ conservation is the only means of conserving
a species. It also provides a back-up solution to in-situ conservation projects. A few examples of ex-situ
conservation are seed banks, botanical gardens, pollen storage, tissue culture and genetic engineering



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