Chapter 16 : HEREDITY AND EVOLUTION

1. Define Sex Determination. What are the methods (mechanisms) of sex determination in different organisms?
   ANS
   
   • The mechanism to determine the sex of an individual is known as sex determination.
   • Different species use different mechanisms for sex determination.
     • In some species, the temperature at which fertilized eggs are kept determines whether the organism developing in the egg would be male or female.
     • In human beings the sex is determined genetically.
     • In animals like snail, the individual can change the sex, indicating that their sex is not determined genetically.
2. Answer in short.
   1. Name the ancestor of Broccoli, Kohlarabi, Kale, Cauliflower and Cabbage.
   2. Name at least two organisms which are now extinct and are studied from their fossils.
   3. Name five varieties of vegetables which have been produced from 'Wild cabbage' by the process of artificial selection.
   4. Choose the one term from the following which includes the other three: Broccoli, Wild cabbage, Cauliflower, Cabbage
   
   ANS
   
   1. Wild cabbage
   2. Ammonite, Trilobite, Dinosaur
   3. Broccoli, Kohlrabi, Kale, Cauliflower and Cabbage
   4. Wild cabbage
3. Explain : Variation.
   ANS
   
   • The occurrence of differences among the individuals of same species is known as variation.
   • Organisms which reproduce asexually or vegetatively show very little variation.
   • Organisms which reproduce sexually show distinct variations.
   • In sexual reproduction, crossing over of genes during meiosis gives rise to new combinations of characteristics. This results in variation among the individuals of species.
   • All these variations, however, do not have equal chance of survival in the environment in which they find themselves.
   • Different individuals get different advantages of these variations.
   • Selection of variants by environmental factors forms the basis of evolutionary process.
4. Write a note on Heredity.
   ANS
   
   • Heredity means continuity of features from one generation to another.
   • Heredity can be defined as "the transmission of characters from parents to the offspring" or "the tendency of every individual to resemble his/her parents".
   • Due to heredity, eggs laid by a sparrow hatch into sparrows only and a dog gives birth to pups only.
   • Hereditary information is present in the fertilized egg (zygote) which develops into an organism of a particular type only.
5. Write a note on Sex Determination.
   ANS
   
   • In humans, the sex is determined by the genes located on chromosomes.
   • Genes are inherited from parents.
   • Out of 23 pairs of chromosomes, 22 pairs are autosomes which are similar in male and female.
   • In female, the 23rd pair has two similar chromosomes called X-chromosome.
   • In male, one chromosome in 23rd pair is X chromosome and the other is Y chromosome which is smaller in size.
     
     
   • All eggs (ova) of female are similar. Each egg contains 22 autosomes and one X chromosome.
   • 50% sperms in male have X chromosome and 50% have the Y chromosome (along with 22 autosomes).
   • If a sperm carrying X chromosome fertilizes an egg, the zygote develops into a female.
   • If a sperm carrying Y chromosome fertilizes an egg, the zygote develops into a male.
6. Explain the following as Evidence of Evolution: (i) Homologous organs (ii) Analogous organs (iii) Fossils
   ANS
   
   1. HOMOLOGOUS ORGANS
      • The organs having the same internal structure but different functions are called homologous organs.
      • The basic design of the bones of forelimbs of a frog, a lizard, a bird, a bat and a man is similar in in their internal structure but they perform different functions.
      • This is an evidence that the forelimbs of all these organisms have evolved from a common ancestor with same basic internal structure.
   2. ANALOGOUS ORGANS
      • The organs with different basic design but similar appearance and similar function in different organisms are called analogous organs.
      • The wings of insects and the wings of birds have different structure but they perform similar function.
      • The presence of analogous organs in different animals give the evidence that they may not have evolved from a common ancestor but they perform similar function to survive in prevailing environment.
   3. FOSSILS
      • The impressions of dead organisms that lived in the past are known as fossils.
      • The dead bodies of organisms are decomposed by micro-organisms. Sometimes, due to environmental conditions, these bodies do not decompose completely and are preserved in the earth.
      • For example, a dead leaf trapped in mud is not decomposed completely and the mud forms impression of the leaf by setting around it as a mould. It then hardens to form a rock and retains the impression of the leaf. Thus, fossil of a leaf is formed.
      • The age of the fossils can be estimated by carbon dating method. The age is determined by the radioactive isotope of carbon (C-14).
      • Ammonite, Trilobite and Dinosaur are the examples of fossils. The age of their fossils is determined by carbon dating method.
7. Define 'Speciation'. Explain how speciation occurs.
   ANS
   
   • The process by which new species develop from the existing species is known as speciation.
   • When the population of a species splits into two groups separated geographically, new species are formed.
   • The geographical isolation leads to reproductive isolation and there is no gene flow between two separated groups of the population.
   • Some variation arises in individuals due to natural selection.
   • Due to the process of random change in gene frequency (genetic drift), the individuals (of two groups) become so different that they cannot reproduce with each other. This may take thousands of years.
   • There can be more ways like DNA changes, the change in the number of chromosomes, the inability of the germ cells of two isolated groups to fuse with each other, etc. which can lead to speciation.
   • Thus, new species come into existence.
8. Write a note on 'Expression of inherited characters' OR Explain how genes control characteristics.
   ANS
   
   • Gene is a unit of heredity.
   • Genes are located on DNA in a linear order.
   • Each gene synthesizes a specific protein responsible for the expression of a characteristic.
   • Consider the height of a plant as a characteristic. The height of a plant depends upon the amount of a particular growth hormone.
   • The synthesis of hormones is catalyzed by specific enzymes and the synthesis of enzymes is regulated by genes located on DNA.
   • If the enzyme is synthesized in large amount, a lot of hormone will be produced and the plant will be tall.
   • If the gene has an alteration that makes the enzyme less efficient, less hormone will be produced and the plant will be dwarf.
   • Thus, characteristics (traits) are controlled by genes.
9. Write a brief note on Evolution.
   ANS
   
   • Evolution is gradual formation of new species from pre-existing primitive organisms by constant and relatively long time changes.
   • Evolution is the sequence of gradual changes in primitive organisms from which new species have been formed.
   • It is a constant process that started since the origin of life and took millions of years. It is continuous and will occur in future, too.
   • The great variety of living organisms on earth is the result of evolution.
10. Explain : Acquired characteristics (traits).
    ANS
    
    • Acquired trait means a trait developed by an organism in response to the environment.
    • It is not inherited from parents.
    • For example, if the weight of an organism is reduced due to starvation, it would not change the DNA of germ cells. Thus, reduced weight is not a trait inherited by the future generation of starving organism.
    • Other examples of acquired traits are: (i) Cut tail of a mouse (ii) a man knowing how to swim (iii) a man speaking German language (iv) a scar on the body of a man due to accident.
    • These all are traits which cannot be passed on to the next generation as these are changes in non-reproductive cells of the body.
11. Explain : Inherited Characteristics (Traits).
    ANS
    
    • A trait of an organism caused by some change in its DNA is known as inherited trait.
    • Inherited traits can be passed on to the progeny of the organism.
    • Example: Suppose there is a population of red beetles in green bushes. If a colour variation arises during reproduction and a beetle green in colour is produced. Since this change is the result of a change in the DNA of reproductive cells, it is an inherited trait which can be passed on to the next generations.
    • This is the essence of the concept of evolution.
12. Write a brief note on Evolution of eyes.
    ANS
    
    • The eye is an important organ for animals.
    • It is a so complicated organ that it cannot have been generated by a single DNA change.
    • The eyes of animals have been created in stages over many generations.
    • First of all, eyes were formed in planaria (flat worm). These eyes were very simple just like 'eye spots' which could detect light.
    • These eyes provide a survival advantage to planaria.
    • The development of eyes seems to be a very popular adaptation.
    • The eyes in animals like insects, octopus, invertebrates and vertebrates have quite different structures suggesting that the evolution of eyes has occurred in stages.
13. Write a brief note on Evolution of Feathers.
    ANS
    
    • An evolutionary change produced in an organism for one purpose may later on become more useful for an entirely different function. Evolution of feathers is an example of this fact.
    • In some dinosaurs feathers provided insulation in cold weather but they could not be used for flying. Later, they might have become useful for flying.
    • Birds, however, adapted to flight. Thus, presence of feathers in birds indicates that birds are closely related to reptiles (like dinosaurs).
14. Explain : Evolution by Artificial Selection.
    ANS
    
    • The evidences for evolution suggest that very dissimilar looking structures can evolve from a common ancestor.
    • Different looking organisms can in fact be created from the same ancestor by artificial selection in place of natural selection.
    • The farmers have produced entirely different looking vegetables like cabbage, broccoli, cauliflower, kohlrabi and kale from the plant of wild cabbage by artificial selection.
    • Some farmers, in an attempt to have very short distance between the leaves of wild cabbage, produced the commonly used 'cabbage'.
    • Some farmers opted for the arrested flower development of wild cabbage and produced 'broccoli'.
    • Some farmers opted for sterile flowers of wild cabbage and developed 'cauliflower'.
    • When farmers opted for swollen parts of wild cabbage, it resulted in the evolution of 'kohlrabi'.
    • Those farmers who wanted to grow large leaves of wild cabbage produced a leafy vegetable called/kale'.
    • Thus, wild cabbage is the common ancestor and cabbage, broccoli, cauliflower, kohlrabi and kale are the varieties of wild cabbage which have been obtained by artificial selection.
15. Write a note on Human Evolution.
    ANS
    
    • To study human evolution tools like digging of earth, time-dating, study of fossils and DNA sequencing have been used.
    • There is a great variety of human forms and features across the earth.
    • This diversity of features was the basis of different human races. The human races were identified commonly on the basis of the colour of their skin. They were named as white, black, yellow and brown.
    • It is now a well-known fact that the sop called human races have not evolved differently. All human beings are a single species called 'Homo sapiens'.
    • It has been established scientifically that we lived for past few thousand years and our genetic footprint can be traced back to our African roots,i.e. we all came from Africa.
    • A couple of thousand years ago, some of our ancestors left Africa while others stayed back. Those who left Africa spread over the planet from Africa to different parts of Asia, Australia and America.
    • They went in groups, sometimes separating from one another and mixing with one another. Some of them even moved in and out of Africa.
    • This led to evolutionary changes like in all other species.
16. Explain Mendel's contribution.
    ANS
    
    • Mendel performed experiments for explaining the transmission of characteristics (traits) from parents to their offspring.
    • He performed experiments on Pisum Sativum (Garden Pea) and worked out the main rules of inheritance.
    • He studied the inheritance of some of the pairs of contrasting characters like tall and short plants, white and violet flowers, round and wrinkled seeds, axial and terminal flower positions, etc.
    • When Mendel crossed a tall plant (with TT traits on DNA) with a dwarf plant (with tt trait on DNA), the F₁ generation was found to be tall. There were no dwarf or medium height plants in F₁ generation. Thus, only one of the two parental characters was seen in F₁ generation.
    • When the plants of F₁ generation were used to obtain F₂ generation, 25% of the plants were dwarf and 75% were tall.
    • Thus, in F₁ generation both the characters of tallness and dwarfness were inherited from the parents but only the character of tallness was expressed because tallness was dominant trait and dwarfness was recessive trait. [Dominant trait is denoted by capital letter (T) and recessive trait bt small letter (t)].
    • The plants having TT or Tt traits for height were tall and those with tt trait were dwarf. A single trait T is enough for making a plant tall but for dwarfness tt traits are required.
      
      
    • In other experiment, Mendel selected two different traits in a plant. He crossed a plant having yellow and round seed with a plant having green and wrinkled seeds.
    • In F₁ generation, all the plants were with yellow and round seeds indicating that yellow and round are dominating traits.
    • When the plants of F₁ generation are self-pollinated, the plants along with parental combinations (yellow and round seeds, green and wrinkled seeds) new combinations (yellow and wrinkled seeds, grren and round seeds) are also formed in F₂ generation.
    • This indicates that yellow seeds/green seeds traits and round seeds/wrinkled seeds traits are independently inherited.
      
      
      
      
      
17. 
    ANS
    

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.
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    ANS