Chapter 17: OUR ENVIRONMENT

1. Explain : Environment.
   ANS
   
   • DEFINITION: All organisms including plants, animals, micro-organisms and human beings and their physical surroundings with which they interact is called environment.
   • All biotic and abiotic components of the environment are interlinked and interdependent for maintaining environmental balance.
   • Environment varies from place to place due to variation in climate, soil type and topography.
   • All organisms adjust to their environment for survival and any change in any component of the environment may cause discomfort and affect the normal life of the organism.
2. Explain : Ecosystem.
   ANS
   
   • DEFINITION: An interacting system formed by the biotic community together with its physical environment is called ecosystem.
   • An ecosystem may be of small size or large size.
   • There are mainly two types of ecosystem based on the kind of habitat: (i) Aquatic (ii) Terrestrial.
   • Aquatic ecosystems include fresh water ecosystems like rivers, springs, ponds and lakes as well as marine ecosystem formed by oceans.
   • Terrestrial ecosystems include forests, grasslands and deserts.
   • Every ecosystem possesses a specific structure and performs definite functions.
   • Every ecosystem gradually merges into another one.
3. Explain : Components of ecosystem.
   ANS
   
   • An ecosystem consists of mainly two types of components: (A) Biotic components (B) Abiotic components.
   • Biotic components include all living organisms like producers, consumers and decomposers.
   • Abiotic components include non-living factors such as soil, water, light, temperature, wind, humidity, rain, inorganic nutrients and dead organic matter.
   • BIOTIC COMPONENTS:
     (i)Producers:
     • Producers are autotrophic organisms.
     • They possess chlorophyll and produce food througfh the process of photosynthesis.
     • Green plants in terrestrial ecosystem and various algae in aquatic ecosystem act as producers.
     
     (ii)Consumers:
     • Consumers are heterotrophic organisms.
     • They cannot synthesize their food.
     • They consume other organisms and their products as food.
     • They are divided into following four categories.
       1. HERBIVORES (First order consumers): These organisms obtain their food from plants.
       2. CARNIVORES(Secondary/Tertiary level consumers): They predate upon herbivores and other carnivores. If they consume herbivores, they are second order consumers.If they consume other carnivores, they are third (and higher) order consumers.
       3. OMNIVORES: They consume food from both plants and animals.
       4. DECOMPOSERS: They obtain food by decomposing dead bodies of plants and animals. They convert complex organic matter into simple organic molecules and then transform them into inorganic molecules.
   • ABIOTIC COMPONENTS: All nonliving components of an ecosystem are included in abiotic components and divided into two categories.
     1. CLIMATIC factors which include temperature, water, light, wind, mineral elements, and topography of habitat.
     2. EDAPHIC factors which include soil structure and composition.
4. Explain food chain giving suitable example.
   ANS
   
   • DEFINITION: A sequence of living organisms in a community in which one organism consumes another organism is called food chain.
   • Each link of a food chain forms a trophic level.
   • Producers form first trophic level, herbivores form the second level and carnivores form the third level. Thus , a food chain usually starts with producers and ends with carnivores.
   • Food chains are of two types (i) Grazing food chain (ii) Detritus food chain.
   • A grazing food chain begins with chlorophyllous producers and extends through herbivores, carnivores and decomposers.
   • A detritus food chain begins with decomposers and passes through detritus feeding organisms in soil to organisms feeding on detriytus feeders.
   • EXAMPLE : Terrestrial food chain
     
     
   • EXAMPLE : Marine food chain
     
     
   • ENERGY TRANSFER (FLOW) IN A FOOD CHAIN
     • A food chain describes how energy and nutrients move through an ecosystem.
     • Producers (autotrophs) are at the first trophic level. They produce energy.
     • Herbivores (primary consumers) are at the second trophic level. They obtain energy from the producers.
     • Carnivores (secondary and higher level consumers) are at next higher trophic levels. They obtain energy from herbivores or previous level carnivores.
     • Thus, chemical energy produced by autotrophs from sunlight is transferred progressively to next trophic levels.
     • Flow of energy in a food chain is unidirectional and does not revert back to the previous trophic level.
     • For example, energy captured by producers does not go back to sun, energy captured by herbivores does not go back to producers and so on.
5. Explain Food Web with example.
   ANS
   
   • A large number of food chains exist in an ecosystem and many organisms act as a link in more than one food chain.
   • The network formed by the interconnected food chains in an ecosystem is called a food web.
   • This means that the various food chains in an ecosystem do not operate in isolation but they operate in the form of a network of food chains called food web.
   • EXAMPLE:
     
     
6. Write a note on Biological Magnification.
   ANS
   
   • Pesticides like DDT and other chemicals are widely used to protect crops from diseases and pests. Most of these chemicals are non-biodegradable.
   • Due to uncontrolled use of such chemicals, their level increases in the soil and water bodies.
   • These chemicals enter the body of plants and aquatic animals and then they get accumulated progressively at each trophic level.
   • This phenomenon is called Biological Magnification.
7. Mention some global problems.
   ANS
   
   • Global problems are faced not only by individual but by the whole planet and potentially all the people.
   • Some of the major global problems are:
     

     (i) Climate change (ii) Global warming (iii) Deforestation (iv) Depletion of ozone layer
     (v) Loss of biodiversity (vi) Scarcity of water (vii) Problems of waste disposal 
     (viii) Maritime safety (ix) Pollution

8. Write a note on Ozone layer and its depletion.
   ANS
   
   • Ozone layer is located in the stratosphere which is about 50 km high in atmosphere from earth's surface.
   • This layer absorbs UV-radiation from sunlight and prevents it from reaching earth's surface> Ultraviolet rays have harmful effect on living organisms.
   • FORMATION OF OZONE
     
     • Oxygen molecules absorb ultraviolet photons and break down into two oxygen atoms by the process of photo-dissociation or photolysis.
       O₂ ----> O + O
     • The free oxygen atom combines with oxygen molecule to form a molecule of ozone.
       O + O₂ ----> O₃
   • DEPLETION OF OZONE LAYER
     • The phenomenon of depletion of ozone layer was first noticed in the year 1980.
     • It was observed that about 40-50% depletion of ozone layer had occurred over South polar region. Such a large depletion is called 'Ozone Hole'.
     • Later, such ozone holes were also noticed in North polar region.
     • It is probable that ozone holes may develop in other regions with human population.
     • Development of ozone holes depends on the prevalent wind, climatic conditions and suspended particulate matter in the atmosphere.
     • The main factor responsible for the depletion of ozone layer is the addition of chloride ions (Cl^-) in the atmosphere.
     • Chlorine reacts with ozone and removes atoms of oxygen(O) one by one. One chlorine atom can decompose 100,000 molecules of ozone in this manner.
     • Almost 80% of total depletion of ozone layer in the stratosphere is done by chlorofluorocarbons (CFCs). Freon is a CFC used in refrigerators and air-conditioners.
9. Explain : Biodegradable waste and non-biodegradable waste.
   ANS
   
   • BIODEGRADABLE WASTE:
     The waste materials which are broken down by biological processes are called biodegradable. Vegetables, fruits, torn clothes, paper, etc., are examples of biodegradable substances.
   • NON-BIODEGRADABLE WASTE:
     The waste materials which cannot be decomposed by biological processes are called non-biodegradable. Plastic bags, plastic bottles, glass, polythene, etc., are examples of non-biodegradable substances.
10. How the amount of house-hold waste can be reduced?
    ANS
    We can reduce house-hold waste by the following practice:
    • Buy loose fruits and vegetables in order to avoid packaging.
    • Avoid buying disposable items such as razors and pens.
    • Use reusable nappies.
    • Uae reusable carry-bags.
    • Use rechargable batteries.
    • Donate old clothes and shoes to the needy.
    • Reuse the back of papers and envelops.
    • Collect kitchen waste in bags or containers and as soon as they are filled dispose off them properly.
    • Some waste materials can be used to generate extra income if managed properly.

Chapter 18 : MANAGEMENT OF NATURAL RESOURCES

1. What creates serious danger for existence of humans and their culture?
   ANS
   Indiscriminate and rampant use of natural resources like water, land, forests, minerals etc. creates danger for existence of humans and their culture.
2. Mention three R's which can save the environment.
   ANS
   Reduce, Recycle and Reuse are the three R's which can save the environment.
3. Define natural resources.
   ANS
   Naturally occurring resources which cannot be created by man and which can be used for the maintenance of life are called natural resources. Water, land, forests, minerals, plants and animals are examples of natural resources.
4. Define wildlife.
   ANS
   Wildlife means animals which are not domestic, plants which cannot be grown by agriculture and certain micro-organisms.
5. Mention reasons for the depletion of forests.
   ANS
   Rapidly increasing population, industrialization and urbanization are the main reasons for depletion of forests.
6. What leads to Greenhouse effect?
   ANS
   Deforestation and wide use of fossil fuels lead to Greenhouse effect.
7. What do you mean by social forestry?
   ANS
   Social forestry means people's participation in planting more and more fast growing trees on available land such as boundaries of fields, road-sides and along canals.
8. Name bird species considered as 'endangered'.
   ANS
   Great Indian Bustards, Florican, Hornbill, etc. are considered endangered bird species.
9. Name reptiles which are considered endangered species.
   ANS
   Python, wall-lizard, crocodile and some types of tortoise are considered as endangered reptile species.
10. How many sanctuaries and National parks are there in our country?
    ANS
    In our country there are 441 wildlife sanctuaries and 88 National parks.
11. Mention the sources of fresh water.
    ANS
    Rainfall, river streams and ground water are major sources of fresh water.
12. How dams are useful to the society?
    ANS
    Dams are useful to the society in the following ways:
    1. Water stored in dams can be used for irrigation to the crop fields throughout the year by a network of canals.
    2. Water stored in dams can be supplied to people after proper treatment.
    3. Water falling from the dams can be used to generate electricity.
13. Why do we need to manage our resources?
    ANS
    
    • Earth's resources fulfill our needs for food, cloths, fuel, furniture, water, vehicles, etc.
    • These resources are limited but their demand is increasing due to rapid rise in population.
    • Proper management ensures equitable distribution of resources so that all people can benefit from them.
    • Proper management takes into consideration the damage caused to the environment by wasteful use of these resources and minimizes the damage.
    • For example, the damage caused by cutting of trees can be set off by growing new trees.
    • Thus, we need to manage our resources for long term benefits of resources and to reduce the harmful effects resulting from their use.
14. "It will be a huge error if man continues to believe that all natural resources are unlimited." Explain.
    ANS
    
    • Man depends on natural resources for his requirements.
    • Man has been using natural resources indiscriminately to live luxurious and comfortable life.
    • In fact, the amount of natural resources on the earth is limited and the rapidly growing population leads to faster exploitation of the resources. This causes environmental imbalance.
    • Indiscriminate and rampant use of natural resources have created serious challenges for the existence of humans.
    • Therefore, it will be a huge error if man continues to believe that all natural resources are unlimited.
15. How recycle can save environment?
    ANS
    
    • Recycling means collecting the used and discarded items of paper, plastic, glass, metals and other scraps and use them for making fresh objects.
    • Recycling reduces wastes and solves dumping problems.
    • It reduces pollution.
    • It allows us to use natural resources for longer time.
    • Thus, recycle can save the environment.
16. How can we conserve the forests?
    ANS
    We can conserve the forests in the following ways:
    
    • By adopting scientific methods for harvesting the forests.
    • By scientifically monitoring rates of forestation and deforestation.
    • By protecting forests from fire.
    • By preventing unauthorized felling of trees.
    • By planting fast-growing trees.
    • By adopting social forestry, i.e., by planting fast-growing trees on available land by people.
17. Give an example of local people working traditionally for conservation of forests.
    ANS
    
    • An example of local people working traditionally for conservation of forests is the Bishnoi Community in Rajasthan. For them conservation of forests and wildlife is a religious tenet.
    • The Government of India has instituted 'Amrita Devi Bishnoi National Award' for wildlife conservation.
    • Amrita Devi Bishnoi had sacrificed her life along with 363 others for the protection of Khejri trees in Khejrali village of Rajasthan in 1731 AD.
18. Mention the consequences of loss of forest cover.
    ANS
    Loss of forest cover results in increase in soil erosion, decrease in fertility of land, increase in amount of CO₂ in the atmosphere causing Greenhouse effect, decrease in rainfall, changes in regional and global climate and loss of biodiversity.
19. What is the difference between sanctuaries and National parks?
    ANS
    
    • In a sanctuary wildlife is protected but some necessary human activities are allowed.
    • In National parks wildlife is allowed to survive and grow without any human interference.
20. Who are the stakeholders of forests?
    ANS
    The stakeholders of forests are:
    
    1. The people who live in and around the forest.
    2. The Forest Department of Government which owns the land and controls forest resources.
    3. The industries which use various forest products as raw materials.
    4. The Wildlife and Nature enthusiasts interested in conserving the nature in its original form.
21. Write a note on Chipko Andolan.
    ANS
    
    • The Chipko Andolan (Hug-the-trees movement) is an example of people's participation in conservation of nature.
    • The Andolan took place in early 1970s in a remote village 'Reni' in Gharwal.
    • It was causede by the dispute between local villagers and a logging contractor who was allowed to fell trees in the forest near the village.
    • One day when contractor's workers came to the forest to cut the trees the men folk of the village were absent but women from the village reached the forest quickly and clasped the tree trunks preventing the workers from felling the trees.
    • Thus, Chipko Andolan saved the forest trees.
22. Explain: Water-related problems.
    ANS
    
    • More than 40% of world's population lives in arid and semi-arid regions.People living in such regions have to spend major part of their life in gathering water.
    • Saurashtra, Kuchchh and North Gujarat are such regions in the state of Gujarat.
    • A huge amount of wealth and manpower is used in obtaining potable water, water for agriculture and water for industries.
    • Water level in rivers, ponds and lakes are going down due to over-exploitation of such resources.
    • Wet-lands are becoming dry and ground water levels are going further down.
    • These are all water related problems.
23. Explain: Water management.
    ANS
    Water management means a program to provide adequate supply of good quality water for different purposes without harming the water source.
    Some of the approaches to water management are:
    1. In hilly and flood-prone areas, reservoirs, ponds or dams should be constructed so that rain water can be stored. This water becomes ground water by slow percolation.
    2. Canals should be constructed from the areas of excess water to the desert (dry) areas.
    3. Domestically used water should be used for irrigation after recycling.
    4. Sea-water should be made drinkable by removing salts by distillation. This method is used in Bhavnagar (Gujarat).
    5. Wasteful and excessive use of water should be prevented wherever possible.
24. What steps could be taken to conserve energy resources?
    ANS
    Following steps can be taken to conserve energy resources:
    1. We can use efficient technology to reduce the consumption of non-renewable sources.
    2. Non-conventional and renewable sources should be used wherever possible.
    3. Lights, fans, television set and other appliances using electricity should be switched off when not needed.
    4. Stairs should be used instead of lift for up to two to three floors in buildings.
    5. Pressure cooker should be used to save fuels.
    6. Public transport should be used instead of private vehicles.
    7. Bicycles can be used for short distances.
25. 
    ANS