Lesson: Our Environment

Question: 1

Which one of the following is an artificial ecosystem?

(a) Pond

(b) Crop field

(d) Forest

Solution:

Question: 2

In a food chain, the third trophic level is always occupied by:

(a) Carnivores

(b) Herbivores

(d) Producers

Solution:

Question: 3

An ecosystem includes:

(a) All living organisms

(b) Non-living objects

(d) Sometimes living organisms and sometimes non-living objects

Solution:

Question: 4

In the given food chain, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level?

Grass → Grasshopper → Frog → Snake → Hawk

(a) 5 k J

(b) 50 k J

(d) 5000 k J

Solution:

Question: 5

Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as:

(a) Eutrophication

(b) Pollution

(d) Accumulation

Solution:

Question: 6

Depletion of ozone is mainly due to:

(a) Chlorofluorocarbon compounds

(b) Carbon monoxide

(d) Pesticides

Solution:

Question: 7

Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called:

(a) Decomposers

(b) Producers

(d) Carnivores

Solution:

Question: 8

In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of:

(a) Heat energy

(b) Light energy

(d) Mechanical energy

Solution:

Question: 9

Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the:

(a) Food web

(b) Ecological pyramid

(d) Food chain

Solution:

Question: 10

Flow of energy in an ecosystem is always:

(a) Unidirectional

(b) Bidirectional

(d) No specific direction

Solution:

Question: 11

Excessive exposure of humans to UV-rays results in:

(a) Damage to immune system

(b) Damage to lungs

(d) Peptic ulcers

(a) (i) and (ii)

(b) (ii) and (iv)

(d) (iii) and (iv)

Solution:

Question: 12

In the following groups of materials, which group(s) contains only non-biodegradable items?

(a) Wood, paper, leather

(b) Polythene, detergent, PVC

(d) Plastic, bakelite, DDT

(a) (iii)

(b) (iv)

(d) (ii) and (iv)

Solution:

Question: 13

Which of the following limits the number of trophic levels in a food chain?

(a) Decrease in energy at higher trophic levels

(b) Sufficient food supply

(d) Water

Solution:

Question: 14

Which of the statement is incorrect?

(a) All green plants and blue green algae are producers

(b) Green plants get their food from organic compounds

(d) Plants convert solar energy into chemical energy

Solution:

Question: 15

Which group of organisms are not constituents of a food chain?

I. Grass, lion, rabbit, wolf

II. Plankton, man, fish, grasshopper

III. Wolf, grass, snake, tiger

IV. Frog, snake, eagle, grass, grasshopper

(a) (i) and (iii)

(b) (iii) and (iv)

(d) (i) and (iv)

Solution:

Question: 16

The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about:

(a) 1 %

(b) 5 %

(d) 10 %

Solution:

Question: 17

In the given figure the various trophic levels are shown in a pyramid.

At which trophic level is maximum energy available?

(a) T4

(b) T2

(d) T3

Solution:

Question: 18

What will happen if deer is missing in the food chain given below?

Grass → Deer → Tiger

(a) The population of tiger increases

(b) The population of grass decreases

(d) The population of tiger decreases and the population of grass increases

Solution:

Question: 19

The decomposers in an ecosystem

(a) Convert inorganic material, to simpler forms

(b) Convert organic material to inorganic forms

(d) Do not breakdown organic compounds

Solution:

Question: 20

If a grass hopper is eaten by a frog, then the energy transfer will be from

(a) Producer to decomposer

(b) Producer to primary consumer

(d) Secondary consumer to primary consumer

Solution:

Question: 21

Disposable plastic plates should not be used because

(a) They are made of materials with light weight

(b) They are made of toxic materials

(d) They are made of non-biodegradable materials

Solution:

Short Answer Questions

Question: 22

Why is improper disposal of waste a curse to environment?

Solution:

Waste materials produced by various activities of human beings can be categorised as biodegradable waste and non- biodegradable waste.

Accumulated biodegradable waste causes intolerable smell during the process of decomposition. Such wastes, if allowed to decompose in populated area or near water bodies may result in epidemic.

There is a need to dispose non-biodegrade resources properly. For example, improper disposal of plastics may prevent seepage of underground water.

Therefore, any improper disposal of waste in an area affects the living beings living around that area.

Question: 23

Write the common food chain of a pond ecosystem.

Solution:

A common food chain in a pond ecosystem can be:

Algae---------Protozoa-------Small fish---------Large fish/animals

Question: 24

What are the advantages of cloth bags over plastic bags during shopping?

Solution:

The advantages of cloth bags over plastic bags during shopping are given below:

(a) Cloth bags are made up of biodegradable materials.

(b) Cloth bags can carry more materials.

(d) Cloth bags can be reused.

Question: 25

Why are crop fields known as artificial ecosystems?

Solution:

All the biotic and abiotic components of the ecosystem in a crop field are controlled by the famer. A farmer decides:

· which plant to grow,

· how much to grow,

· when to harvest,

· which pesticides to use, etc.

Therefore, crop fields are examples of an artificial ecosystem.

Question: 26

Differentiate between biodegradable and non-biodegradable substances. Cite examples.

Solution:

Substances that can be broken down into simpler substances by biological processes are said to be biodegradable. Examples, wood, paper, food scrapes, egg shell, etc. These substances can be recycled.

Substances that cannot be broken down into simpler ones by biological processes are said to be non-biodegradable. Examples, plastic, DDT, silver foil, rubber, aluminium, polythene bags, etc. These substances cannot be recycled.

Question: 27

Suggest one word for each of the following statements/definitions

(a) The physical and biological world where we live in

(b) Each level of food chain where transfer of energy takes place

(d) Organisms which depend on the producers either directly or indirectly for

food

Solution:

(a) Biosphere

(b) Trophic level

(d) Consumers or heterotrophs

Question: 28

Explain the role of decomposers in the environment?

Solution:

The decomposers help in decomposing dead bodies of animals and plants. This not only helps in cleaning the environment but also plays an important role in recycling nutrients in the soil.

Question: 29

Select the mis-matched pair in the following and correct it.

(a) Biomagnification $—$ Accumulation of chemicals at the successive trophic

levels of a food chain

(b) Ecosystem $—$ Biotic components of environment

(d) Parasites $—$ Organisms which obtain food from other living organisms

Solution:

(b) Correction: Ecosystem consists of both biotic and abiotic components of the environment

Question: 30

We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

Solution:

An aquarium is an artificial ecosystem which needs to be maintained by us. A pond or a lake is a natural ecosystem which is self-sustaining.

Long Answer Questions (8)

Question: 31

Indicate the flow of energy in an ecosystem. Why is it unidirectional?

Justify.

Solution:

Generally, the flow of energy is:

Sun → primary producer → primary consumer (herbivore) → secondary consumer (carnivore) →Tertiary consumer (carnivores)

Energy is transferred along food chains from one tropic level to another. It does not revert back. The amount of available energy decreases from one stage to the next. Thus, it is unlikely for the energy to flow in the reverse direction.

Hence, it is said to be unidirectional.

Question: 32

What are decomposers? What will be the consequence of their absence in an ecosystem?

Solution:

Decomposers are non-green microorganisms. The decomposers help in decomposing dead bodies of animals and plants. They clean the environment and recycle nutrients in the soil.

In the absence of decomposers not only will the garbage of wastes pile up, there will be increase in pollution and there will be no natural replenishment of soil.

Question: 33

Suggest any four activities in daily life which are eco-friendly.

Solution:

Any four activities in daily life which are eco-friendly are:

a) Use of paper bag/cloth bag instead of plastic /polythene bag

b) Plantation of trees

c) Switching of lights/fans when not in use

d) Avoiding waste of water through taps, leakage in pipes, etc.

Question: 34

Give two differences between food chain and food web.

Solution:

Food chain	Food Web
A food chain is a series of living organisms that depend on the others in the chain for their sources of nutrients and energy.	A food web shows how different food chains are connected to each other and how the energy flows through an ecosystem.
It is a simple chain of organisms at different tropic levels.	It is a complex chain of many interlinked food chains.

Question: 35

Name the wastes which are generated in your house daily. What measures would you take for their disposal?

Solution:

Some of the wastes generated in our house and measures taken for their disposal:

Wastes	Measures to dispose
Kitchen waste	Preparing a compost pit for kitchen waste
Paper wastes like newspaper, bags etc.	Separating biodegradable and non-biodegradable wastes and disposing them accordingly. Paper wastes should be given for recycling.
Vegetable/fruit peels	These should be disposed near plants/trees for decomposition.
Leakage of water through pipes and taps.	Repair of pipes and taps on a regular basis should be done.

Question: 36

Suggest suitable mechanism(s) for waste management in fertiliser industries.

Solution:

Sewages and harmful gases are the main wastes produced in a fertilizer factory.

Some of the steps that can be taken for the waste management are:

Using catalytic converter: Catalytic converters should be fitted in the chimneys for reducing the amount of gaseous pollutants.

Treatment of sewage: Sewage from the factory should be sent to effluent treatment plant. Once effluent is treated, the clean water can then be sent to the nearest water bodies and the sludge can be allowed to decompose.

Question: 37

What are the by-products of fertiliser industries? How do they affect the environment?

Solution:

The by-products of fertiliser industries are gases like SO₂ and NO. These are harmful to us. They cause air pollution and are responsible for acid rain.

Question: 38

Explain some harmful effects of agricultural practices on the environment.

Solution:

Modern agricultural practices include use of fertilisers and chemicals for increasing agricultural outputs. This has a negative impact on the environment. Some of these impacts are:

(a) Excessive use of fertilizers changes the soil composition. As a result, many useful microbes are disappearing from the soil.

(b) Too much use of non-biodegradable chemical pesticides has resulted in the biological magnification.

(d) Excessive use of ground water has impacted the survival of living organisms depending on the water.

(e) Use of pesticides has resulted in the extinction of many insects and plants that were found in the field.