Class 12 EVS 2017 Paper

Environmental Science

EVS-class-12-paper-2017.

by Aishwarya Murthy

1  What  happens  to  the  Lion  when  all  the  green  plants  and  trees  are  removed  from  the  forest  ?​

All the biotic and abiotic components are dependent on each other ​

​Green plants are the sources of food and energy for all organisms.

If all green plants disappear from the earth, all the herbivores will die due to the absence of food and so will the carnivores.

​2 Mention any three factors which force the villagers move into cities.

Villagers are moving into cities in

search of jobs,

opportunities and

better facilities.​

lack of food

natural hazard

poverty

racial discrimination​

3 Which was recommended by the Montreal convention and protocol as a substitute for CFC ?

use of HCFCs (Hydrochloric fluorocarbons) as a substitute for CFCs is being recommended on temporary basis because HCFCs are relatively less damaging to ozone layer as compared to CFCs, but they are not completely ozone safe.​

​4 Give two examples for high yielding dwarf wheat varieties.

The important high yielding varieties include

‘Kalyan Sona’,

‘Sharbati, Sonara’,

‘Sonalika’

were released

5 Write one difference between paleolithic age and Neolithic age​

​6 Mathew is shocked by the TV news in the clearance of ten thousand trees to construct the new airport and as a result he planted twenty thousand plant saplings along with his friends. How does the clearance of trees will result in soil erosion ?

​Deforestation causes soil erosion . As the trees hold the soil in place , when trees are removed the soil moves and causes degradation .

​It also causes flood and soil is not able to hold water.

Classify the following into Biotic and Abiotic components Nitrogen, Cyclops, Sparrow, Amino acid, Penicillium and Humidity.​

BIOTIC:

Sparrow

Penicillium

​Cyclops

​

ABIOTIC:

Nitrogen

Amino acid

Humidity​

​8 a BMC

Biodiversity Management Committees (BMC)

​created for “promoting conservation, sustainable use and documentation of biological diversity

​8 b NBA

National Biodiversity Authority (NBA) it performs facilitative, regulatory and advisory functions for the Government of India on issues of conservation, sustainable use of biological resources

​8 c CITES

Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

established to regulate international trade in species threatened with extinction. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.​

​9 Differentiate between anthropocentric and eco-centric environment.

​One view is that humans are the dominant and important species on the planet earth. That gives them the power to manipulate and use nature for their own benefit. This view is “human centred” and thus it is called anthropocentric.

​

​

​An extension of the above view seeks respect for all life and demands reverence towards the entire environment. Such a non-anthropocentric approach that talks of ethical responsibility towards other species and even ecosystems is also called ecocentric.

​10 What is meant by village forests ?

Village forest is a forest in which the villagers guards the forest. They were allowed to stay on in the reserved forests on the condition that they worked free for the forest department in cutting and transporting trees, protecting the forest from fires.

​11 Define carbon tax.

​A carbon tax is a fee imposed on businesses and individuals that works as a sort of "pollution tax." The tax is a fee imposed on companies that burn carbon-based fuels, including coal, oil, gasoline, and natural gas.

12 Expand CSE and mention two of its important publications.

Centre for Science and Environment (CSE)

​

Two of their interesting publications are ‘Down to Earth’ and ‘Gobar Times’ magazine for children.​

13 a Give reason: ​Density of tiger, leopards, lions, deer etc. is determined by the pugmarks left by the animals in a defined area.

​Pugmarks of each individual animals are unique and different from one others

​

Study of pug marks can provide the following information reliably if analyzed skillfully:

Presence of different species in the area of study.

• Identification of individual animals.

• Population of large cats (tigers, lions etc.).​

​13 b Give reason: Primary succession takes at very long time as compared to secondary succession which is very fast.

Secondary succession usually occurs faster than primary succession because the substrate is already present. In primary succession, there is no soil and it needs to form. This process takes time, as pioneer species must colonize the area, they must die, and as this happens over and over again, soil forms.

​

​Primary succession is a process of gradual changes in the ecosystem, that starts where no living organisms are there e.g., bare rock, newly created pond or reservoir. In this period weathering of rocks and formation of soil takes place which is time-consuming process.

​14 Raveena is a research student. She goes to her uncle's village for her research 4 work. In the village she saw that her uncle is using DDT as pesticide and his farm is closer to an electroplating industry which releases cadmium. Raveena goes and educates her uncle about ill effects of DDT and cadmium.

​14 a Name and explain the biological phenomenon associated with accumulation of DDT in the food chain

​

​Biomagnification is the build up of toxins in a food chain

​The DDT concentration is in parts per million. As the trophic level increases in a food chain, the amount of toxic build up increases

14 b ​ Write the causes and effects of cadmium

Cadmium exposure occurs from ingestion of contaminated food

​

Acute inhalation exposure (high levels over a short period of time) to cadmium can result in flu-like symptoms (chills, fever, and muscle pain) and can damage the lungs.

​It mainly affects kidneys and bones. It is also a carcinogen by inhalation. Cadmium can accumulate in liver, kidneys and bones

​15 b How acid rain does promote the heavy metals to affect the metabolism of plants and microorganisms ?

​Acid rain is formed when the air that contains acidic gases emitted mostly from power plants industries and automobiles, combines with the rain drops

​Acid rain kills their gametes affecting the life cycles and productivity

​

​Acidic medium promotes leaching of heavy metals such as aluminum, lead and mercury. Such metals when percolate into ground water affect soil microflora/ micro fauna. The soil becomes lifeless. Absorption of these toxic metal ions by plants and microorganisms affect their metabolism.

​16 Energy conservation has been recognized as a national issue for long time. As a responsible citizen of India, how would you consume energy for various activities of your daily life ?

​To conserve energy we can do the following steps-

1.use less electrical appliances.

2.we should use solar panels.

3.use man power it will keep you fit also so travel short distance by cycle.

4.always take out plug of electrical appliances when there is no use of them.

​17 a Explain how excess of chemical fertilizers will result in algal blooming.

​Some algal blooms are the result of an excess of nutrients (particularly phosphorus and nitrogen) into waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants.

​17 b Mala and Rama both are living in the same village. Mala burns wood and cow dung as a fuel for basic necessity. But Rama prepared bio gas from bio waste. If you compare both Mala and Rama, you will prefer who is the better and why ?

​Rama is better.

​Biogas burns completely without giving smoke and any residue. So, it is a better fuel than animal dung cakes.

​Burning of animal dung cake causes lot of pollution whereas biogas is a smokeless fuel.

​18 a How will you differentiate the three types of iron ores ?

​Most iron ores found in the country are of three types – Haematite, magnetite and limonite.

Haematite is red in colour, called ‘red ore’ and has 68% iron.

Magnetite is dark brown in colour called ‘black ore’ and has 60% iron.

Limonite is yellow in colour and has 35% iron.​

​18 b Define Bio-mining. Why it is economically feasible ?

to use microorganisms to extract metals from its ores known as “biomining” or ‘ecological engineering’, which may be an economical and environmentally preferable way to mine metals.

​Biomining is economically feasible specially with low- grade ores

White Grub and Shoot Moth larva feeding on different parts of the same plant. what does this depict

​A niche is unique for a species while many species share the habitat. No two species in a habitat can have the same niche.

​For example, a large number of different species of insects may be pests of the same plant but they can co-exist as they feed on different parts of the same plant.

​19 ii a Difference between Estuaries and Deltas

The estuary is an area where saltwater of sea mixes with fresh water of rivers. It is formed by a tidal bore.

Delta is a low triangular area of alluvial deposits where a river divides before entering a larger body of water.

​

19 ii b Differentiate western and eastern ghats​

​

​20 a “Urbanization and industrialization produces colossal quantities of waste.”

Urbanization and industrialization produces colossal quantities of waste. Quantity of Solid waste form domestic and industrial sources is growing problem. They may be biodegradable when they may be used for generation of biogas. The nonbiodegradable waste is dumped in land fills

​

​Liquid wastes such sewage from domestic sector and industrial effluents are usually discharged without any treatment causing pollution of rivers and lakes

​20 b Discuss why slash and burn method of farming causes deforestation.

​Shifting cultivation or Jhoom farming is a 12000-year old practice and a step towards transition from food collection to food production. It is also known as slash and-burn method of farming.

​

Annually about 5 lakhs ha (hectares) of forest is cleared for this type of farming. In this type of cultivation there is a limited use of tools with not very high level of mechanization.

However, this method of cultivation causes extreme deforestation, as after 2-3 years of tilling, the land is left to the mercy of nature to recover.

​20 c Mention any four states of India which still practices shifting cultivation.

shifting cultivation is practiced in the states of Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura and Andaman and Nicobar Islands.

21 (i) State any four sources of CFC

• Refrigerants for refrigerators, automobiles and air-conditioners.

• Cleaning agents for semi-conductors and precision parts.

• Foaming agents for insulating materials and packing cushions.

• Propellants for aerosol sprays.​

​21 ii How the presence of CFC in atmosphere will damage ozone layer ?

Gaseous CFCs can deplete the ozone layer when they slowly rise into the stratosphere, are broken down by strong ultraviolet radiation, release chlorine atoms, and then react with ozone molecules.

​21 iii Write any two consequences of ozone layer depletion.

​Ozone depletion in the stratosphere has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole.

UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth's atmosphere, given that the ozone layer is intact.

​But, UV-B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers.

23 How does alum help in water treatment ?​

​Aluminium sulphate (alum) is the most common coagulant used for water purification.

​

​To remove such smaller particles, alum is added. Alum causes flocculation. Flocculation is a process through which all the finer insoluble particles form large particles called flocs. These flocs then can easily settle and thus are removed from water

24 Write the factors deciding the movement rate of ground water

Porosity is where groundwater can flow, and permeability and gravity (the hydraulic gradient) determine how fast it can get there

Groundwater movement is comparatively very slow as compared to surface water. The flow depends on slope and permeability. When the water table is above the surface water level in some hilly areas, groundwater flows out as a spring.

​25 What is the role of potassium in the nutritional management of crops ?

Potassium is associated with the movement of water, nutrients and carbohydrates in plant tissue.

It's involved with enzyme activation within the plant, which affects protein, starch and adenosine triphosphate (ATP) production. ...

​

Other roles include:

​

Increases root growth and improves drought resistance

​26 Name any four non-porous materials which are used to prevent the evaporation of crops

​Non-porous materials like papers, asphalt, plastic foils or metal foils can also be used for preventing evaporation losses

​27 (a) What is the reason behind the foul smell of the river water?

​Different types of waste like, industrial, domestic, religious

These get settled and cause foul smell.​

​27 b Why the fishes lied dead on the shore ?

​Fishes die in water(river) due to pollution.

​Pollution like plastic waste, domestic or industrial waste and also due to oil spills, they consume this air and water which causes death and brings them to shore.