CBSE Class 10 Science Our Environment Assignment Set G

ECOSYSTEM :
• The term Ecosystem was coined by Tansley. According to him Ecosystem is a symbol of structure and function of nature.
• The term Ecology was coined by Reiter.
• The term Ecology was first of all described y E.Haeckel.
• Father of India Ecology - Prof. Ramdas Mishra. *8 The boundaries of ecosystem are indistinct and have an overlapping character with each other.
• “The total group of living things and environment of factors present in a particular place is called as ecosystem/”
• It means any structural and functional unit of the environment that can be identified and studied is called as ecosystem.
• Ecosystem may be natural or artificial, permanent or temporary. Large ecosystem is called as biome such as desert, forest etc.
• Homeostasis : Self maintainable characteristic is found in ecosystem. It means an ecosystem maintains the balance between the different trophic levels. Each trophic level controls the other trophic level in an ecosystem.
• Cybernetics : A science of self control [homeostasis] in an ecosystem is called as “cybernetics”

(a) Types of Ecosystem :
Natural (e.g. lake, forest, grassland etc.) or man made (e.g. an aquarium crop field etc.)
(i) Temporary : e.g. rain-fed pond etc.
(ii) Permanent : e.g. lake, forest etc.
• An ecosystem may be as small as a drop of pond water. Such small ecosystem is called as micro ecosystem. Human activities may modify or convert natural ecosystem into man made ecosystem. Cutting tree or forests and the conversion of land for tree plantation or agriculture etc. are some of the examples of conversion of natural ecosystem to man made ecosystem.

(b) Components of Ecosystem :
Ecosystem consists of two components :
(i) Biotic component (ii) Abiotic component (environment, soil etc.
(i) Biotic components : Different biotic components are connected, through food chain or other relations. That is why it is said that all the living organisms comes under biotic components. Food available for biotic components can be synthesized, from inorganic raw material by the autrophs only.
• Biotic components are of thee types which are essential for ecosystem.

(A) Producers : All the autotrophs of ecosystem are called as producers. The green plants are the main producers. Green plants absorb solar energy and convert it into chemical energy. It means energy enters into the ecosystem through the produces. The solar energy is the only ultimate source of energy in ecosystem. This energy is available to the remaining living organisms through the medium of food.

(B) Consumers: All the heterotrophy of the ecosystem are known as consumers. Animals are the main consumers. They directly (herbivorous) or indirectly (carnivorous) depend upon the producers. There are various types of consumer which are as follows :
• Primary consumers : They are also known as secondary producers because they synthesize complex materials in the cells by the digestion of food which they obtain from the plants. Such living organisms which obtain food form the producers are known as primary consumers. Such as all the herbivores of ecosystem.
• Secondary consumers : Animals which feed upon primary consumers and obtain their food. It means those carnivorous which kill and eat the herbivorous. So that they are called as predators e.g. Dog, Cat, Snake etc. In aquatic system whale fish is a secondary consumer.
• Top consumers : Those animals which kill other animals and earth them by they are not eaten by other animals in the nature .e.g Lion, Vulture, Peacock and Man (human) in our ecosystem. Man and peacock may be omnivorous.

(C) Decomposers or Microconsumer : Those living organisms which decompose the dead bodies of producers and consumers and release mineral substances again into the soil which are present in the dead bodies. So that decomposers help in mineral into the soil which are present in the dead bodies. So that decomposers help in mineral cycle. Only because of this land is the main source of minerals. The main decomposers in ecosystem are - bacteria and fungi which decompose continuously dead animals and dead plants.

(D) Scavengers : Vulture never kills any animal so that vulture is a scavenger, not a decomposer. The process of decomposition takes place outside the body of bacteria. The break down of the food materials takes place in the body of vulture and minerals are released into the soil in the form faecal material. They are also called as reducers because they decomposes and remove the dead bodies of the organism.

(c) Structure of an Ecosystem :
The structure of an ecosystem is characterized by the physical organization of biotic & abiotic components. The major structural features of an ecosystem are species composition, stratification, trophic organization and nutrients.

(i) Species composition : Each ecosystem has its own type of species composition. Different ecosystems have different species composition. A great variety of species is found in forest ecosystem, whereas a few species occur in a desert ecosystem.
(ii) Stratification : The organisms in each ecosystem from one or more layers or strata, each comprising the population of particular kind of a species.
(iii) Trophic organization : Food relationship of producers and consumers is another way to predict ecosystem structure. In an ecosystem there an be only 4 - 5 successive trophic levels because
(A) All the food available in one tropic level is not being eaten by another animal in the next trophic level.
(B) All the food eaten by an animal is not useful, thus a part of energy containing food is passed out as
waste products.
(C) A large amount of energy is lost in respiration to drive organisms metabolism and thus, there is not much energy left to support higher trophic levels.
• The amount of nutrients such as nitrogen, phosphorus and calcium present in the oil at any given time is termed as standing state.

(d) Functions of an Ecosystem :
(i) Productivity : Ecosystem helps of maintain the productivity, of the system. The rate of organic matter or biomass production is called as productivity. The study of biomass production in the ecosystem is called as production ecology.
(ii) Energy flow : Energy flow in an ecosystem is a key function of an ecosystem. It determines the following two laws of Thermodynamics :
(A) First law : It states, that energy can neither be created nor destroyed, but can be transferred from one from to other.
(B) Second law : It states, that every energy change involves the degradation or dissipation of energy, from concentrated to the dispersed form due to metabolic functions, so that only a small part of energy is stored in the biomass.
(iii) Nutrient cycles : All living organisms get matter from the biosphere component i.e. lithosphere, hydrosphere and atmosphere. Essential elements or inorganic substances are provided by earth and are required by organisms for their body building and metabolism, they are known as biogeochemical or biogenetic nutrients.
(iv) Development and stabilization : This function is necessary for the development and giving stability to various life form’s by undergoing certain modifications.

FOOD CHAIN :
• The chain of organisms which involves transfer of energy from one trophic level to next trophic level is called as food chain.
• The flow of food or energy is an ecosystem is called Food chain. Those organisms which join with the food chain are termed as Trophic levels.
• Usually, there are four trophic levels present in the ecosystem because level of energy decreases during the flow of energy from one trophic level to the another trophic level.
First trophic level [T₁] : Producers
Second trophic level [T₂] : Primary consumers
Third trophic level [T₃] : Secondary consumers
Fourth trophic level [T₄] : Top consumers
• The flow of energy occurs in an ecosystem from the first trophic level to the fourth trophic level in the food chain. These are five trophic levels also found in a highly complex ecosystem in which tertiary consumers are present in between the secondary consumer and top consumers, then fifth trophic level (T₅) formed by the top consumers.

(a) Types of food Chain :
There are three types of food chains which are found in nature.
(i) Predator food chain (ii) Parasitic food chain (iii) Saprophytic food chain
• Predator food chain extends from producers through herbivores to carnivores, parasitic food chain stat from producers but ends with parasites and saprophytic food chain starts with decomposers. Producers are autotrophic organisms which synthesize organic food from simple inorganic raw material through photosynthesis by utilizing solar energy. A part of food synthesized by the producers is used in their body building, while the rest is utilized in providing energy for various life activities.

Some common predator food chains are given below :
• Vegetation - Grasshopper - Shrew - Hawk
• Vegetation - Rabbit - Wolf - Tiger
• Vegetation - Frog - Snake - Peacock
• Plant - Rat-  Snake - Hawk.

Aquatic food chains :
• Phytoplanktons - Zooplanktons - Small crustacians - Predator insect - Small fish-  Large fish - Crocodile
• Phytoplanktons - Zooplanktons Small fish Large fish Shark
• Phytoplanktons - Zooplanktons - Fish - Crane - Hawk.

FOOD WEB :
In nature, the food chins are not isolated sequences but are rather interconnected with one another. “A network of food chains which are interconnected at various trophic levels, so as to form a number o feeding connection amongst different organisms of a biotic community is called as food web. The food web opens several alternate pathways fro the flow of energy. Generally, food web operates according to test and food performances of the organisms at each trophic level, yet availability of food source and other compulsions are equally important. The concept of food web appears to be more real than that of simple food chain. The food web increases the stability of an ecosystem by providing alternate source of the food and allowing endangered population to grow in size. Many food chains are interlinked together to form food web in a big ecosystem in which flow of food takes place through many directions such as forest. A food web which is present in forest ecosystem is a highly complex and permanent (stable) type of food web.
• As much as food web complexes are there as much ecosystem is permanent or stable, such type of ecosystem does not degenerate naturally and continues for longer time period.
• The ecosystems which have simple food webs are not more stable. It means that this type of food web can be finished at nay time. Any attack or cutting of plants can causes the destruction of while ecosystem e.g. Gondwana forest is converted into the desert by the activity of men. this is the example of desertification by men.

DIFFERENCE BETWEEN FOOD CHAIN AND FOOD WEB

ECOLOGICAL PYRAMIDS :
An ecological pyramid is a graphical representation of an ecological parameter like number of individuals or amount of biomass or amount of energy present in various trophic levels of a food chain with producers forming the base and top carnivores from the tip. Ecological pyramids could be upright, inverted or spindle shaped. There are three important parameters of each trophic level in a food chain i.e. number of individual, amount of biomass and amount of energy.

(a) Pyramid of Number :
In this type of pyramid the number of individual organisms in various trophic levels is shown. These pyramids may be upright or inverted. The number of organisms of any trophic level depends upon the availability of organisms which are used as food on lower level so that availability of food is the main factor. These producers are of two types
:
(i) Phytoplanktons : They are the inactive floating plant, because hey do not have locomotors organs e.g. Diatoms.
(ii) Phytonektons : These plants swim actively in water, because in them locomotary organs are present. Usually flagella are preset in these plants. e.g. Chamydomonas and dinoflagellates. The number of phytoplanktons and phytonketons are higher per unit area of water because they are unicellular.
• In a tree ecosystem the pyramid of number is inverted. This is called as parasitic ecosystem because bird depend upon tree and parasites depend upon birds. Therefore with the increase in the number of trophic levels, the number of the organisms increases sequentially.
• Pyramid of number shows biotic potential of an ecosystem.
• The number of members of any particular species in a favorable condition is called as their biotic potential.
• When the number of the members of any species increases then it is called as population explosion.

(d) Pyramid of Biomass :
The biomass of each trophic level is shown by this pyramid. Mostly these pyramids are also upright (erect). e.g. Tree ecosystem.
• Pyramid of biomass in aquatic ecosystem is inverted, because in this producers are micro organisms and their biomass is lesser than other trophic levels.
• Pyramids of biomass show the standing crop of ecosystem. It means total amount of living matter at a particular time in an ecosystem is called as standing crop.
• Total amount of nonliving matter in an ecosystem is called as standing state.

(c) Pyramid of Energy :
It always remains erect, because flow of energy is not cyclic. i.e. during the flow of energy at each trophic level goes on decreasing.
• According to the 10% law of Linderman the 90% part of obtained energy of each organism is utilized in their various metabolic activities and only 10% energy transferred to the next trophic level. So that 90% energy is lost at each trophic level therefore, top consumers like lion etc., are weakest ecologically.
• Pyramids of energy show the productivity of any ecosystem.
• Plant community : All types of plants present at a particular place to form a community, is called as plant community.
The distribution of any species at a place depends upon social nature of the species which indicates cooperation between them.
• Synecology : The ecological study of any plant community is called as “gynecology”.
• Phytosociology : The study of structure of plant community is known as “phytosociology”
• Phytogeography : The study of distribution of the plants on the earth is called as “phytogeography”. Some characteristics of plant community are as follows :

(i) Species diversity : There are many verities of organisms found in a community. The total number of species of plants called as population. The ecological study of population is called as Autecology’s. The maximum species diversity is found in tropical forest. The plants are called as flora and animals are termed as fauna. The lowest species diversity is found in Tundra biome or Arctic desert.

(ii) Dominant species : The highest number of plants of a species present in a community is called as dominant species and whole plant community is knows as the name of the species. Such as Prosop is community on Aravali hills and Aravali hills and Pinus community on Himalaya. 
• B.O.D. It shows the deficiency of oxygen in the water. Daphnia is the indicator of B.O.D.

OZONE LAYER DEPLETION :
Between 20 and 26 km above the sea level ozone layer is present and the part of atmosphere containing it is called ozonosphere (Stratosphere). This layer is established due to an equilibrium between photo dissociation of ozone by UV - radiations and regeneration of ozone. The thickness of this ozonosphere averages 5 km. The ozone layer acts as an ozone shield and absorbs the harmful UV - radiations of the sunlight so protect the earth’s biota form the harmful effects of strong UV - radiations. So this layer is very important for the survival and existence of life on earth.

(a) Causes of Thinning of Ozone Layer :
The decline in spring - layer thickness is called ozone hole. Ozone hole is largest over Antarctica and was just short of 27 million sq. km. during September 2003. Main chemicals to be responsible for destruction of ozone - layer are : chlorofluorocarbons (CFCs), halogens (used in fire extinguishers), methane and nitrous oxide. Out of these, most damaging is the effect of CFCs which are a group of synthetic chemicals and are used as collants in refrigenratorsare a group of synthetic chemicals and are used as collants in refrigerators and air conditioners; as cleaning solvents, propellants and sterilant etc. These CFCs produce “active chlorine” in the presence of UV - radiations. These active chlorine radicals catalytically destroy ozone and convert it into oxygen. Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen (O₂) molecule. The higher energy UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone as shown - In 1987, the United National Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.,
• Nitrous oxide: is produced in industrial processes, forest fires, solid waste disposal, spraying of insecticides and pesticides, etc. Methane and nitrous oxide also cause ozone destruction.

(b) Effects of Ozone Layer Depletion :
The thinning of ozone layer results in increase in the UV radiation (in the rage of 290 - 320 nm) reaching the earth’s surface. It is estimated that 5 percent loss of ozone results in 10 per cent increase in UV - radiations. These UV - radiations can :
(i) Increases in incidences of cataract and skin cancer.
(ii) Decrease in the functioning of immune system.
(iii) Inhibit photosynthesis in most of phytoplankton so adversely affecting the food chains of aquatic ecosystems.
(iv) Damage nucleic acids of the living organisms.

MANAGEMENT OF NATURAL RESOURCES :

(a) Introduction :
We often hear or read about environmental problems. These are often global-level problems and we feel helpless to make any changes. There are international laws and regulations, and then there are our own national laws and acts for environmental protection. There are national and international organisations also working towards protecting our environment. The multi crore project of Ganga Action Plan came about in 1985 because the quality of water in the ganga was so poor.

(b) Pollution of the Ganga:
The Ganga runs its course of over 2500 km from Gangotri in the Himalayas to Ganga Sagar in the Bay of Bengal. It is being turned into a drain by more than a hundred towns and cities in Utter Pradesh, Bihar and West Bengal that pour their garbage and excreta into it. Largely untreated sewage is dumped into the Ganga every day. In addition pollution is caused by other human activities like bathing, washing of clothes and immersion of ashes or unburnt matter also. And then, industries contribute chemical effluents to the Ganga’s pollution load and the toxicity kills fishes in large section of the river.

Three R’s to save the environment :
(i) Reduce : This means ‘to use less’. We van save electricity by switching off unnecessary lights and fans. We can save water by repairing leaky taps.
(ii) Recycle : This means that we can collect plastic, paper, glass and metal items and recycle these materials to make required things instead of synthesizing or extracting fresh plastic, paper, glass or metal. In order to recycle, we first need to segregate our waste so that the material that can be recycled is not dumped along with other waste.
(iii) Reuse : This is actually even better than recycling because the process of recycling uses some energy. In the ‘reuse’ strategy, we can simply use things again and again.

(c) need of Manage Our Resources :
Our natural resources are limited with the rapid increase in human population. Due to improvement in health care, the demand for all resources is also increasing. Management of natural resources requires long term perspective to meet the needs and aspirations of future generations. Natural resources should be managed in such a way that every one of the society is benefited from its development. The waste generated from exploration of natural resources should be disposed off safely. For instance, mining causes pollution due to discard of large amount of slag during metal extraction.

SUSTAINABLE DEVELOPMENT :
It is the development which can be maintained for a long time without undue damage to the environment. The objective of sustainable development is to provide the economic well being of the present and the future generations and to maintain a healthy environment and life support system. It encourage forms of growth that meet current basic human needs, thus sustainable development implies a change in all aspects of life. It depend upon the willingness of the people to change their perceptions of the socio economic environmental conditions and use of natural resources.

BIODIVERSITY :
It is the existence of a wide variety of species of plants, animals and microorganism in a natural habitant within a particular environment. Biodiversity of an area is the number of species or range of different life forms found there. Forests are ‘biodiversity hotspots’.

PRACTICES FOR CONSERVATION AND PROTECTION OF ENVIRONMENT :
Conservation means ‘to keep safe’ whereas preservation means ‘to maintain the environment at it is’. Various practices which can help in conserving and protecting our environment are as follows :
• The practice of crop rotation helps in conserving soil.
• Judicious use of fertilizers, intensive cropping, proper irrigating and drainage help in the conservation of soil.
• The treatment of sewage prevents pollution of water bodies and helps in conserving fishes and other aquatic life forms.
• National parks and wildlife sanctuaries should e established throughout the country in order to protect and conserve will animals, birds and plant species.
• New trees should be planted in place of those cut for various purposes, which will protect the earth from excessive heating.
• Harvesting of rain helps in the conservation of groundwater.
• Composting of solid organic waste for biogas and manure.

WILDLIFE :
It means all those naturally occurring animals, plants and their species which are not cultivated, domesticated and tamed.

(a) Conservation :
It is the sensible use of the earth’s natural resources in order to avoid excessive degradation and betterment of the environment. It includes - the search for alternative food and fuel supplies when these are endangered, an awareness of the dangers of pollution and the maintenance and preservation of habitats and its biodiversity.

(i) Steps for conservation of wildlife :
(A) Laws should be imposed to ban poaching or capturing of any animal or bird belonging to an endangered species.
(B) The natural habitats of wild animals and birds should be preserved by establishing National Parks, Sanctuaries and Biosphere reserves throughout the country.
(C) The Government Department should conduct periodic surveys of National Parks, Sanctuaries and Biosphere Reserves to have a knowledge of all the species of wild animals and birds.
(D) More attention should be given to conserve the endangered species of wild animals and birds to prevent their extinction.
(E) Unauthorized cutting of forest trees should be stopped.

STAKEHOLDERS OF FORESTS :
The conservation of forests depend on its forest resources or its various stakeholder, who are as follows :

(a) People Who Live in or Around Forests :
(i) They depend on forest produce, for various aspects of their life.
(ii) The local people need large quantities of firewood, small timber.
(iii) Bamboo is used to make slats for huts and baskets for collecting and storing food.
(iv) Implements for agriculture, fishing and hunting are largely made of wood.
(v) People collect fruits, nuts and medicines from forests, their cattle also graze in forest.

(b) Forest Department of the Government :
(i) Which owns the land and controls the forest resources.
(ii) People develop practices to ensure that forest resources are used in a sustainable manner.
(iii) The forest resources were overexploited after the British took control of the forest.
(iv) Forest department of independent India then owned the land and control the resources of the forest but local needs such as herbs, fruits and fodder were ignored.
(v) Monoculture of pine, teak or eucalyptus have been started which can destroy the bio-diversity of the area.

(c) Industrialist :
(i) Industries consider the forest as a source of raw material for its factories.
(ii) These industries are not interested for the sustainability of the forest in one area as they go to a different area after cutting down all tree in one area.

(d) Wildlife and Nature Enthusiasts :
(i) They are not dependent of the forest but conserve nature and take part in its management.
(ii) Conservationists started with conserving large animals but are now preserving biodiversity as a whole.
(iii) The local people, for instance the Bishnoi community in Rajasthan worked for conservation of forest and wildlife as a religious act. Thus management of forest resources has to take the interests of various stakeholder into account.

TRADITIONAL USE OF FOREST :
• Alpine grasslands in Himalayas were grazed by sheep in summer.
• Nomadic shepherd drove their flock every summer in this area.

(c) Causes of Damages to Forests :
(i) Local people damage forest to fulfill their daily needs.
(ii) Deforestation caused by industrial needs.
(iii) Deforestation caused for development projects like building roads or dams.
(iv) By tourists or in making arrangements for tourists.

(b) Conservation of Forests :
• it includes the following methods :

(i) Afforestation :
It is the practice of transforming an area into forest have not grown there, it involves three types of forestry programmes.
(A) Social and Environmental forestry. It involves raising of trees for firewood, fodder and agricultural implements for the benefit of rural and trial community.
(B) Agro forestry. It is an absolute commercial forestry developed to fulfill the need of various forest based industries. It is done on the fallow land or free-grazing lands.
(C) Urban forestry. In involves growing of ornamental trees along roads, vacant lands and common parts of urban areas.

(ii) People participation in forest management :
(A) The Sal forests in West Bengal got reduced alarmingly in 1972.
(B) Surveillance and policing to protect resulted frequent clash between forest official and the villagers.
(C) The department then changed its strategy and in Asabari forest, villagers were involved in protection of the badly damaged Sal forest.
(D) In return, villagers were given employment and were allowed to collect firewood and fodder at nominal fee.
(E) By 1983, the Asabari forest showed a remarkable recovery.

(iii) Economic growth and Ecological conservation :
(A) Forest resources should be used in an environmentally and developmentally sound manner.
(B) The benefit of controlled exploitation of resources goes to the people and the environment is also preserved.
(C) If the exploitation is too high, economic and social development will be faster but the environment will further deteriorate.
(D) We should use natural resources cautiously so that economic growth and ecological conservation go hand in hand.
(E) Amrtia Devi Bishnoi National Award. In 1731, Amrita Devi Bishnoi sacrificed her life along with 63 persons for the protections of ‘Khejri’ trees in Khejrali village near Jodhpur in Rajasthan. In the memory Government of India have recently instituted this award for Wildlife Conservation.’
(F) Chipko Movement : During 1970, In Reni village of Garhwal, a contractor was allowed to cut trees in a forest near the village. When the contractor’s workers went to the forest to cut trees the woman of
the village hug the tree trunks to prevent the workers from cutting trees, Chipko means ‘hug’ and the movement started by the villagers by hugging tees is called Chipko Andolan’.

WATER AS A BASIC NATURAL RESOURCE :
• It is a valuable national asset.
• It is the main requirement of human being.
• Water is of two types - salt water and fresh water.
• Fresh water is an unlimited natural resource, it can be obtained from three natural resources - rain water, surface water and ground water.
• Human intervention pollutes water and also changes the availability of water in various regions.

(a) Water Sources :
(i) Rain in India re due to monsoon.
(ii) Failure to sustain underground water due to loss of vegetative cover, development of water demanding crop and pollution from industrial effluents.
(iii) Small dams, canals and tank were used for irrigation purpose and to fulfill the basic minimum needs.
(iv) Large dams and canals were made by British as well as our own government.
(v) Due to the mega project, local irrigation methods got neglected and the local people lost control over management of local water sources.
(vi) Large dams and canals were made by British as well as our own government.

(b) Management of Water Resources :
It includes :
(i) Interacted water-shed plan for drinking, irrigation and industrial uses.
(ii) Flood control
(iii) Transfer of surplus water to water deficit basins by inter-linking of rivers.
(iv) Hydro geological survey to identify over-exploited areas.
(v) Artificial recharging of the ground water.
(vi) Mass awareness programmes through public or private agencies.
(vii) Dams : They are massive barriers built across rivers and streams to confine and utilize the flow of water for human purposes such as irrigation and generation of electricity.
• Large dams can also ensure the storage of adequate water.
• Canal system leading from dams transfer large quantity of water upto great distances, e.g. Indira Gandhi Canal or Rajasthan brought greenery to considerable areas.
• Purposes for building a dam :
• Generation of electricity
• Irrigation
• Control of flood which either stops or slows the amount of water in the river.
• Criticism about large dams :
• Social problems : They displace large number of farmers and tribals.
• Economic problems : They consume huge amount of public money without proportionate benefit.
• Environmental problems. As they cause deforestation and loss of biological diversity.

(c) Mismanagement of Water Distribution :
Due to mismanagement in distribution of water, the benefit of contracting a dam goes to few people only. For example, people close to the water source grow water intensive crop like sugarcane and rice
while people farther downstream do not get any water. This resulted in discontentment among the people who has been displaced by building of dam.

(i) Watershed management : It means scientific conservation of soil and water to increase the biomass production.
• Watershed management not only increases the production and income of the watershed community but also overcomes drought and flood.
• It increases the life of downstream dam and reservoirs.
(ii) Water harvesting : It means capturing rainwater where it falls or capturing the runoff water in a local area and talking measures to keep the water clean by not allowing polluting activities to take place

(A) Techniques of water harvesting : Water harvesting techniques are mainly location specific. It is an age - old concept in India.
• Khadins, tanks and nadis in Rajasthan.
• Bandharas and tals in Maharashtra
• Ahars and Pynes in Bihar
• Kulhs in Himanchal Pradesh
• Ponds in kandi belt of Jammu.
• Eris (tanks) in Tamilnadu.
• Suragams in kerala.
• Kattas in Karnataka.
• Due to own control of the local population over exploitation of the local water resources in reduced.

(B) Some of the water harvesting techniques are :
• Capturing of runoff water roof tops.
• Capturing of runoff water from local catchments.
• Capturing seasonal flood water from local streams.

(C) Benefits of water harvesting :
• Provide drinking water.
• Provide irrigation water.
• Increase in ground water resources.
• Reduces storm water discharge, urban flood and overloading of sewage treatment plants.

(D) Advantages of ground water :
• It does not evaporate.
• It spreads out to recharge wells.
• It provides moisture for vegetation.
• It does not provide breeding grounds for mosquitoes.
• It is relatively protected from contamination by human and animal

(E) Traditional water harvesting system :
• The water harvesting structures are mainly crescent shaped.
• Monsoon rains fill ponds behind the structures.
• The large structure hold water throughout the year while most dry up after monsoon.
• The main purpose of this system is to recharge the ground water and not to hold surface water.

15.14 FOSSIL FUELS :
These fuels are obtained from the remain of plants and animals, which got buried beneath the earth millions of years ago, changed into coal, petroleum and natural gas due to excessive heat and high pressure inside

(a) Non-Renewable Energy Sources :
These are energy sources which cannot be replaced easily when the get exhausted and are also called conventional sources of energy. They are used traditionally for many years and take millions of years to form e.g. Fossil fuels.
(i) Coal : It contains carbon and its compound mainly with nitrogen, oxygen, sulphur and hydrogen. It also consists of inorganic matter.
(ii) Petroleum : ‘Petro’ means rocks and ‘oleum’ means oil, petroleum is therefore the oil found in rocks. It is a complex mixture of solid, liquid and gaseous hydrocarbons. It also contains small amounts of other compounds of carbon, hydrogen, oxygen, nitrogen and sulphur. Large reservoirs of petroleum have been preserved by nature for millions of years between porous rocks beneath the earth.

(b) Formation of Non-Renewable Energy Sources :
(i) Formation of coal. Coal is formed organic matter which got buried under the earth 300 million years ago. Due to high pressure and temperature inside the earth, this organic matter changed into coal, that is why, coal is called fossil fuel.
(ii) Formation of petroleum. It is formed by the decay of very small (tiny) marine animals and plant buried under the earth about 400 million years ago. Due to excess of heat and pressure it changed into oil called petroleum. It is a fossil fuel.

(c) Conservation of Coal and Petroleum :
It means more efficient use with regard to economic, social and environmental cost and benefits which result in attainment of higher efficiency, minimisation of wastage and protection of the environment.
• We can conserve coal and petroleum by their judicious use and substituting them by other resources wherever feasible. Conservation of coal and petroleum is a joint responsibility of the industries, citizens and government where each one has significant role in Management of Natural Resources.

(d) Necessity of Judicious Use of Coal and Petroleum :
The fossil fuels, coal and petroleum get exhausted and their combustion pollutes our environment, so a judicious use of these resources is necessary. When combustion take place, oxides of carbon, hydrogen, nitrogen and sulphur are formed. Carbon monoxide is formed instead of carbon dioxide if there is insufficient are. The oxides of sulphur, nitrogen and carbon monoxide are poisonous at high concentrations. Carbon dioxide is a green-house gas which leads to global warming.

(e) Uses of Fossil Fuels :
(i) In thermal power plants and steam engines.
(ii) Petroleum products like petrol and diesel are used as fuel in motor vehicles and ships. Other products like kerosene and LPG are used for cooking purpose.

(f) Management of Fossil Fuels :
The natural gas is a good alternative to fossil fuels like coal and petroleum. The use of alternative source of non-conventional energy such as solar energy, which energy, biomass energy, etc., should be promoted to save the reserves of fossil fuels. Biogas can also be used for various purposes.

Question. Ecosystem term was coined by
(a) Odum
(b) Mishra
(c) Reiter
(d) Tansley

Answer: D

Question. In which of the following trophic levels in any ecosystem the maximum energy is stored ?
(a) Producers
(b) Herbivores
(c) Carnivores
(d) Top carnivores

Answer: A

Question. Pyramids of biomass are
(a) upright or inverted
(b) always inverted
(c) mostly upright
(d) mostly inverted

Answer: A

Question. A biosphere is composed of
(a) living organisms
(b) living organisms and lithosphere
(c) living organisms, lithosphere and atmosphere
(d) living organisms, lithosphere, atmosphere and hydrosphere

Answer: D

Question. In an ecosystem the function of the produces is to
(a) convert organic compounds into inorganic compounds
(b) trap solar energy and convert in into chemical energy
(c) utilize chemical energy
(d) release energy

Answer: B

Question. Vultures in an ecosystem are
(a) predators
(b) scavengers
(c) consumers
(d) top carnivores

Answer: B

Question. In other to maintain proper ecological balance
(a) the existing forests should be cleared and new ones should be planted
(b) some quick growing annuals should be planted if a tree must be cut for other uses
(c) tree must be curt whenever necessary because the underground part performs the useful purpose
(d) a tree should be planted in place of one to be cut

Answer: D

Question. In an ecosystem the
(a) primary producers are more than that of primary consumers
(b) secondary consumers are largest, because they are powerful
(c) primary consumers are out of number
(d) primary consumers are least dependent upon primary producers

Answer: A

Question. Pyramid of energy in a forest ecosystem is
(a) always inverted
(b) always upright
(c) both upright and inverted
(d) first upright then inverted

Answer: B

Question. The importance of ecosystem lies in
(a) flow of energy
(b) cycling of materials
(c) both of the above
(d) none of the options

Answer: C