Class X – Our Environment (PYQs) with solutions

Ans. Secondary consumers will get more energy.

Ans. (i) Oceans, (ii) forests are two natural ecosystems.

Ans. Plants, animals, micro-organisms (any two) are biotic components.

Ans. Green plants prepare their own food by photosynthesis with the help of CO₂, H₂O, sunlight and chlorophyll.

Ans. They prepare their own food from CO₂, H₂O and sunlight from environment. They are consumed by herbivores; therefore, they always occupy first trophic level.

Ans. Herbivores will always be at second trophic level.

Ans. Energy available to primary consumer’s level is 10000 X 10/100 = 1000 J

Energy available to secondary consumer trophic level = 10 1000 100 × = 100 J

Ans. Hawk is a decomposer and have maximum concentration of non-biodegradable chemicals. The phenomenon is called Biomagnification.

Ans. Tea bags and tin cans.

Ans. Trophic level.

Ans. Bacteria and fungi are called decomposer because they breakdown complex organic matter as remains of plants and animals into CO₂, methane and other simple molecules which go into atmosphere and as nutrients to soil.

Ans. Grass will absorb 1% solar energy i.e. 10000 × 1/100 = 100 J

Dear will get 10% of 100 J = 100 × 10/100 = 10 J

Out of this 10 J of energy, only 1 J of energy can be transferred to lion.

Ans. Grass → Insect → Frog → Snake

Frog is a secondary consumer and belongs to 3rd trophic level.

Ans. Forests help to reduce air pollution.

Ans. 1000 × 1/10 = 100 J.

Ans. ‘X’ is primary consumer, ‘Z’ is tertiary consumer in the given figure.

Ans. Minimum use of fertilizers, insecticides and pesticides, can prevent the accumulation of harmful chemicals in our body.

Ans. Fish production will decrease due to formation of excess of algae.

Ans. Producers and primary consumers are first two components in the flow of energy.

Ans. All living organisms and abiotic components of surroundings forms an ecosystem.

Ans. Grass → Deer → Tiger.

Ans. It depicts 10% law in food chain for energy transfer from one trophic level to another.

Ans. Aquarium, crop land, park.

Ans. It is because plastics are not decomposed by micro-organisms. (Note: Now, plastic eating enzymes has been discovered).

Ans. The peacock will also die. The population of rats will increase.

Ans. (i) Second trophic level → Rabbit (ii) Third trophic level → Frog and fox.

Ans. Plants → Deer → Lion

It is given that 100 J of energy is available to lion.

Let the amount of energy available to deer be x Joules.

According to 10% law, 10% energy from deer must have been transferred to lion. So, energy available to deer can be calculated as, 10/100 × X = 100 J, Therefore, x = 1,000 J

Now, let the amount of energy available to plants be y Joules.

According to 10% law, 10% energy from plants must have been transfered to deer. So, energy available to plant can be calculated as, 10/100 × y = 1,000 J

Therefore, y = 10,000 J

So, we have found that energy available to the producer is 10,000 J.

Ans. 1000 J.

Ans. (i) Controlling pollution (ii) Afforestation (iii) Proper Waste Disposal

Ans. Ecosystem is the functional unit of environment.

Ans. Biodegradable substances are those which are broken by micro-organisms and get decomposed. They do not persist in environment for a very long time e.g., paper. Non-biodegradable substances are those which are not broken by micro-organisms. They persist in environment for long time. e.g. plastic, DDT.

Ans. Each level in a food chain is called trophic level. First trophic level is producers.

Ans. An example of food chain is grassland food chain. Its different trophic levels are shown in the given figures

Ans. (i) Decomposers decompose the remains of plants and animals.

(ii) They clean the environment.

(iii) They bring back the raw materials to environment.

Ans. (i) Cloth is biodegradable, does not pollute environment.

(ii) It can be used again like plastic bag and moreover it is eco-friendly.

Ans. (i) Wash vegetables and fruits with saline water and vinegar.

(ii) Shock the vegetables in salt water for few minutes before cooking.

(iii) Boil the vegetables.

(iv) Organic manure and organic eco-friendly pesticides should be used.

Ans.

Ans. The energy of sun is taken by plants and cannot be given back. Herbivore eat plants and cannot give back energy to plants. Carnivores eat herbivores and cannot give back energy to herbivores. It means flow of energy is unidirectional from lower trophic level to higher trophic level.

Ans. Ecosystem is composed of different organisms interdependent upon each other. Biotic and abiotic components are its two main components.

Ans. Pond or lake is a natural ecosystem; several organisms present in it maintain a balance in the ecosystem. Aquarium is an artificial ecosystem in which bacteria convert fish food into ammonia which is harmful for fish. Water needs to be changed regularly. Chlorine water should be dechlorinated otherwise fish will not survive. Air pump is needed to provide oxygen. Artificial ecosystem need utmost care to remain stable.

Ans. If we kill the organisms in one trophic level.

(i) The population of organisms in previous trophic level will increase.

(ii) The population of organisms in next trophic level may decrease.

(iii) It will cause an ecological imbalance in the food chain.

Ans. Food chain is a sequence in which nutrients, food and energy is transferred in systematic way. Lower trophic level has maximum population because energy is available in more extent.

Primary consumers get 10% of energy of producers.

Secondary consumers get 10% of energy of primary consumers.

Tertiary consumers get 10% of energy of secondary consumers i.e. very less energy is available, that is why the trophic levels are limited. Tiger population is decreasing day by day as food is not easily available for them and forests are decreasing due to cutting of trees.

Ans. A terrestrial food chain depicting four tropic levels is shown in diagram.

Ans. According to the 10% law, the amount of energy available will not be sufficient for the survival of the organisms in the 5th trophic level. (A flow chart or a diagrammatic representation showing all the four tropic levels would also be accepted).

According to the 10% law, the amount of energy available will not be sufficient for the survival of the organism in the 5th trophic level.

Ans. • Take a large jar filled with water, oxygen, food and aquatic plants and animals.

• Oxygen/oxygen pump.

• Fish food.

• Aquatic plants/Producers provide O₂ during photosynthesis.

• Aquatic animals/Consumers release CO₂ for the process of photosynthesis.

• Decomposers are also important for natural cleaning of the aquarium.

Ans. Level 1 Plants and algae

Level 2 Herbivores like goat, cow

Level 3 Carnivores like fox, wild cat, mongoose

Level 4 large carnivores, lion, tiger

Ans. If we kill all organisms in one trophic level, then transfer of energy as well as matter to next higher level will stop, it will lead to overpopulation at one particular level, disturb the food chain and cause collapse of ecosystem.

Ans. Energy available at second trophic level of 2000 J

Energy available at third trophic level is 2000 × 1/10 = 200 J

Energy available at fourth trophic level is 200 × 1/10 = 2 J

Ans. Glass, silver foil.

Ans. CFC stands for Chloroflurocarbon

UNEP stands for United Nations Environment Programme.

Ans. UV radiations (Ultra-Violet radiations) are absorbed by ozone layer.

Ans. CFC will deplete ozone layer which prevents UV radiation to reach earth. It causes skin cancer.

Ans. (i) HFCs (Hydrofluorocarbons), (ii) Perfluorocarbons (PFCs) have replaced CFCs.

Ans. It protects earth from harmful UV radiations.

Ans. It saves time and energy by separating them and waste disposal can be done in right way in minimum time.

Ans. (i) Bits of paper (ii) Plastic bottles of water or cold drinks.

Ans. Two causes of depletion of ozone layer are: (i) CFCs (ii) Aerosols

Two harmful effects of depletion of this layer are:

(i) UV radiations can reach the earth and causes skin cancer, harmful to eyes and immune system will be disturbed.

(ii) It may lead to variations in rainfall, ecological disturbance.

Ans. They need to be told that cows and other animals eat polythene which is fatal for them. Coloured polythene is also very harmful for vegetables and fruits.

Ans. Paper bags, jute bags, bags of biodegradable materials are eco-friendly and carrying your own shopping bag is also more convenient.

Ans. Schools must teach students to protect environment. They should make paper bags and distribute to small shopkeepers regularly so that gradually their habits will change.

Ans. 10 to 16 km

Ans. UV rays

Ans. Global warming.

Ans. Water is one of the most precious natural resources that has vital importance in our lives. It is an essential component of the human body and is used almost everywhere in our day-to-day activities, such as cooking, washing, in agriculture and industries. It is an indispensable part of our life, without which the life on earth is not possible. However, the amount of fresh water available for sustaining life is very less. So, it is very important to conserve water. For creating awareness among people, we can adopt the following two ways.

(i) Door to door campaigning. (ii) Nukkad Nataks

Ans. Underground water table can be recharged through rainwater harvesting. Rainwater harvesting is a process by which rain water is collected and stored for the purpose of recharging the ground water or for future use like for irrigation and agriculture, for livestock, etc. In India, rainwater harvesting is an old tradition, which is followed till now in many parts of India. For example, bawris are traditional architectural rainwater harvesters that were built for collecting water, in the state of Rajasthan.

There are two ways of rainwater harvesting:

(i) Surface runoff harvesting: In urban areas, rain water that flows away from the surface can be collected and used for various purposes.

(ii) Rooftop rainwater harvesting: The rainwater on the roofs of the buildings is collected through canals that drains the water into ground water reservoirs. This stored water can later be utilised.

It is formed by action of UV light on oxygen.

Ans. (i) More use of disposable items like paper plates, plastic and polythene which are recyclable.

(ii) Change in packaging Suggestion. Reuse of plastic containers

Ans. Hawk will have highest concentration of non-biodegradable chemicals. This process is called biomagnification.

Ans.

Two habits to dispose of non-biodegradable wastes are:

(i) Use of separate dustbins for biodegradable and non-biodegradable wastes,

(ii) Reuse of things such as polybags, etc.,

(iii) Recycling of wastes

(iv) Use of cotton /jute bags for carrying vegetables etc.

Ans. Ozone is a molecule containing three atoms of oxygen (O₃). It is a highly poisonous gas present in the upper layers of the atmosphere.

Formation of ozone: The UV radiations from Sun split some molecules of oxygen (O₂) apart into free oxygen atoms (O + O). These atoms then combine with oxygen molecules to form ozone.

Ozone layer shields the surface of the earth against damaging UV radiations of the Sun.

Ans. (i) Global warming occurs due to increase in number of vehicles and over use of fossil fuels.

(ii) Due to excessive use of deodrants, perfumes, CFCs, etc. ozone layer is getting depleted.

(iii) Air pollution occurs due to industralisation.

(iv) Wastes causes pollution due to release of sewage in water bodies.

(v) Pollution of soil occurs due to overuse of chemicals is agriculture.

Ans. Soil and water conservation in a scientific way is called ‘watershed management’.

Advantages: (i) Increase in production and income of watershed communities, (ii) Mitigate draughts and floods, (iii) Increase the life of downstream dam reservoir.

Ans. Maximum level of biomagnification occurs in human beings because of progressive accumulation. We get very small amount of energy as only 10% of previous energy gets transferred to each trophic level.