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Q  1. What will happen if we kill all the organisms in a trophic level?

Solution

If we kill all the organisms in a trophic level, then flow of energy would be disturbed in the food chain and hence balance of nature in terms of energy transfer would get disturbed.

Q  2. Describe the concept of food chain with the help of an example.

Solution

Food chain can be defined as the sequential arrangement of organisms in which all organisms are inter-related and depend on each other for their food. For example: The light energy of sun is trapped by green plants i.e. producers, who constitutes the first trophic level. These green plants are eaten by herbivores which, in turn, become source of food for carnivores.

Q  3. What is coliform?

Solution

It is a group of bacteria found in human intestine whose presence in water indicates contamination by disease causing micro-organisms.

Q  4. Give any two ways in which biodegradable substances would affect the environment.

Solution

(i) They may produce foul smell during decomposition process. (ii) They may produce some harmful gases such as ammonia, methane, carbon dioxide, etc., which can further cause global warming.

Q  5. List any two functions of food chain in an ecosystem.

Solution

Functions of food chain: 

(i) Food chain maintains ecological balance. 

(ii) It helps in converting solar energy into usable chemical energy for various organisms. 

Q  6. Mention any two effects of ozone depletion.

Solution

The harmful effects of ozone depletion are following: i. It can lead to various deadly diseases like skin cancer. ii. As due to the depletion of ozone layer UV rays fall straight on earth and thus cause severe damage to eyes.

Q  7. (a) What are decomposers? (b) State in brief the role of decomposers in the environment.

Solution

(a) Decomposers are microorganisms that obtain energy through chemical breakdown of dead animals or plants and other organic wastes. 

(b) Decomposers decompose dead bodies of plants and animals, and hence act as a cleansing agents of environment.

Q  8. Name the type of compounds which are used as refrigerants and in fire extinguishers and deplete the ozone layer in the atmosphere.

Solution

CFCs :Chlorofluorocarbons

Q  9. Which one of the following food chain is better and why? (a) Plant → Man (b) Plant → Goat → man

Solution

(a) is better Reason-In a shorter food chain maximum transfer of energy takes place according to ten percent law of nature.

Q  10. Mention types of ecosystem in a biosphere.

Solution

There are two types of ecosystem in a biosphere which are: i. Natural ecosystem ii. Artificial ecosystem

Q  11. What would happen to the environment if decomposers were not present?

Solution

There will be no decomposion of wastes which would create foul smell and may cause pollution.

Q  12. List two man made ecosystems.

Solution

(i) Aquarium (ii) Cropland

Q  13. Who constitutes the first trophic level in a food chain?

Solution

Producers (green plants) constitutes first trophic level in a food chain.

Q  14. How can we help in reducing the problem of waste disposal? List any two ways.

Solution

(a) By segregating biodegradable and non - biodegradable wastes. (b) By reusing and recycling the non - biodegradable waste.

Q  15. Use of paper bags is more environment friendly than the use of polythene bags for packaging. Justify.

Solution

Paper bags are biodegradable and get decomposed by the action of microorganisms in due course of time while polythene bags are non-biodegradable.

Q  16. In a certain study conducted on occurrence of DDT along food chains in an ecosystem, DDT in grass was found to be 0.5 ppm (parts per million), in sheep it was 2 ppm and in man it was 10 ppm. Why was the concentration of DDT maximum in case of man?

Solution

In accordance with the concept of biomagnification, the maximum accumulation of a non-biodegradable pollutant is maximum in the highest trophic level. Since, DDT is non-biodegradable it accumulates at each trophic level and since, man is at the highest trophic level, there is maximum accumulation of DDT observed in them. 

Q  17. What are the biotic components of an environment?

Solution

The biotic component of an environment includes producers, consumers and decomposers.

Q  18. Describe the concept of trophic levels briefly.

Solution

In a food chain, trophic levels are defined as the number of steps that are followed by one another in the process of energy flow and are also dependent on each other for food. Different trophic levels are as follows- i. Producers- They form the first trophic level and are able to manufacture their own food (green plants). ii. Primary consumers- They form the second trophic level and are generally plant eaters (herbivores). iii. Secondary consumers- They form the third trophic level and are flesh eaters (carnivores). iv. Tertiary consumers- They form the fourth trophic level and feed on secondary consumers (top carnivores).

Q  19. (a) What is an ecosystem? List its two main components. (b) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain.

Solution

(a)Ecosystem is a self sustaining system where the biotic and abiotic organisms of various communities live with each other. The two components of the ecosystem are - biotic and abiotic. Biotic system consists of all the living organisms of particular area like humans, animals etc. and the nonliving component consists of air, minerals, soil, water and sunlight. (b) Ponds are the example of natural ecosystem whereas an aquarium is an example of artificial ecosystem. Ponds do not need to be cleaned but aquarium needs to be cleaned because an aquarium does not contain soil and decomposing bacteria which helps in degrading complex organic substances into simple inorganic substances. But ponds or lakes have this facility. Therefore, it does not need to be cleaned.

Q  20. Differentiate between biodegradable and non-biodegradable waste materials.

Solution

Differences between biodegradable and non-biodegradable waste are following:   S.No Biodegradable  waste Non-biodegradable waste i. The substances that are easily decomposed by microorganisms. The substances that are not decomposed by microorganisms. ii. These substances easily mix with the soil after short interval of time. E.g. paper These substances are not able to mix with the soil even after a long interval of time. E.g. plastic

Q  21. Phytoplanktons → Zooplanktons → Fish → Fish-eating bird. In the above foodchain, which of the organisms will have (i) Maximum available energy? (ii) Maximum concentration of pesticides?

Solution

(i)Maximum available energy : Phytoplanktons (ii)Maximum concentration of pesticides : Fish eating bird.

Q  22. List two main components of our environment.

Solution

Two main components of our environment are: a. Abiotic b. Biotic

Q  23. Define the process of incineration. Why it is considered as the safe method of waste disposal?

Solution

Incineration is the process of disposing off domestic and industrial (chemical) waste safely without polluting the environment. It is considered as a safe method of waste disposal because in this process waste materials are burnt at very high temperature of 1000^o C so that they can be converted into gases and water vapours. The ash thus left behind is also devoid of any harmful particles.

Q  24. Which one of the following is biodegradable? Agricultural residue, plastics, insecticides, sewage.

Solution

Agricultural wastes and sewage.

Q  25. Observe the food chain Plant (1000 KJ) → Goat → Lion (a) If autotrophs occupying the first tropic level are called producers what are herbivores called as? (b) How much energy does the lion get in the above food chain?

Solution

(a) Primary consumers (b) When 10% law is applied, the goat gets 100 kJ and lion gets 10 kJ

Q  26. The flow of energy in the food chain is unidirectional. Why?

Solution

In a food chain, energy enters through solar energy through producers. This energy is transferred from producers to other organisms. Also some amount of energy that enters the food chain is lost to the environment in the form of heat. As energy can only be transferred from producers to other organisms and not backwards, it is said that  energy flow in a food chain is unidirectional. 

Q  27. What are the probable damages due to ozone layer depletion?

Solution

Due to ozone layer depletion, ultraviolet rays reach the earth and cause certain ill-effects which are bad for us and for crops. Some of them are: (i) Exposure to UV rays can lead to greater incidence of skin cancer, cataracts or other damages to the eye and immune deficiency. (ii) An excess of ultraviolet light decreases crop yield and reduce population of phytoplanktons, zooplanktons and certain fish larvae that are important constituents of aquatic food chains. (iii) It may also disturb global rainfall, causing ecological balance and bring about reduction in global food supplies.

Q  28. (a) Given two examples of decomposers present in any ecosystem. (b) How is the presence of decomposers crucial in the ecosystem?

Solution

(a) Bacteria and fungi are examples of decomposers. (b) Decomposers are essential components of the ecosystem. They decompose dead remains of plants and animals and their waste organic products into simpler, inorganic substances. The latter are released into the environment for their reuse as raw material by the producers. These, therefore, provide space for new life to settle in the biosphere.

Q  29. What do you mean by the term biomagnification?

Solution

Biomagnification can be defined as a phenomenon in which each trophic level in a food chain experience an increase in the concentration of harmful non–biodegradable chemicals like D.D.T and other pesticides.

Q  30. Producers always occupy the first trophic level in any food chain. Why?

Solution

Producers always occupy the first trophic level in any food chain because only producers have the ability to trap solar energy with the help of chlorophyll and synthesize their own food.

Q  31. Define the term biological magnification.

Solution

Biomagnification or biological magnification is the increase in the level of non - biodegradable substances in the successive trophic level of a food chain.

Q  32. What is the role of decomposers in the environment?

Solution

Decomposers help in recycling of materials by breaking down the waste materials and dead remains of pants and animals.

Q  33. Differentiate between autotrophs and heterotrophs.

Solution

  S.No Autotrophs Heterotrophs 1. The organisms that can prepare their own food using inorganic material from the environment. E.g. green plants. The organisms that cannot prepare their own food and depend on others (producers) for their food. E.g. animals and human beings. 2. Autotrophs use CO₂ and release O₂ in environment. Heterotrophs use O₂ and release CO₂ in environment.

Q  34. What do you mean by ozone depletion? Also mention the cause of ozone depletion briefly.

Solution

Ozone depletion generally refers to the process in which ozone layer undergoes thinning continuously over a period of time. The major cause of depletion of ozone layer is the release of harmful chlorofluorocarbons like methane and oxides of nitrogen into the atmosphere. These particles are released from vehicles; air conditioners etc and produce active chlorine in presence of UV rays. These rays destroy the ozone and thus cause ozone depletion.

Q  35. In the following food chain 5 J energy is available to man. How much energy was available at producer level? Plant → sheep → man

Solution

Applying 10% law, if 5 J energy is available to to man, 50 J is available to sheep and at last 500 J is available at producer level

Q  36. "Industrialization is one of the main causes of deterioration of environment". List any four reasons in favour of this statement.

Solution

i. Noise and air pollution caused due to industrialization disturbs the environment. ii. Waste released from industries leads to water pollution. iii. SO₂, NO₂ etc. emitted by the industries, are toxic. iv. Radioactive radiations emitted by nuclear power stations are toxic to living organisms.

Q  37. Which of the following materials are biodegradable? Glass, leather, glucose, silver foil.

Solution

Glucose and Leather.

Q  38. Select the biodegradable wastes from the following: DDT, Crop residue, Leather and glass.

Solution

Crop residue and leather

Q  39. Name any two non-biodegradable wastes.

Solution

Plastic bags, polythene, insecticides etc. (any two)

Q  40. Pesticides are useful to farmers yet considered as pollutants. Given reasons.

Solution

Pesticides kill insects and pests thereby protect the crops but these pesticides remain on the crops which enter the food chain and get accumulated in the organisms at the top most tropic level that causes diseases. When these are washed away by rain river water, it also causes pollution.