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13. Our Environment

Environment - Everything that surrounds us is environment. It includes both living organisms (biotic) and non-living (abiotic) components.
Example :
Biotic Factors -Plants, Animals, Microbs etc
               Abiotic factors : Air,Water, Soil, Light,.
Ecosystem :
An ecosystem is a structural and functional unit of biosphere, in which comprising of all the interacting organism in an area together with the non-living components of the environment .
Types of Ecosystem
Natural ecosystem : The ecosystem which exists in nature on its own is called natural ecosystem.
Example forests, ponds and lakes.
Forrests are considered as natural ecosystem because they have species of plants and animals which interact with each other without human intervention
Artificial ecosystem : The ecosystem which are created and maintained by humans are called artificial or manmaid ecosystem
example garden, Crop-field and aquarium
An aquarium can be considered as an artificial ecosystem because whatever it is consists of green plants, fishes, waters and sand etc all are added by the humans.
There is no recycling and self cleaning because of the absence of the natural decomposers so an aquarium need to be cleaned regularly.
Two main components of ecosystem are biotic and abiotic components
Example : Biotic components : Plants, Animals, etc
Abiotic components : temperature, rainfall, wind, soil and minerals.
On the basis of nutrition, biotic components are divided into three classes.
1. Producers : Those organism which can produce there own food by the process of photosynthesis are calles producers. They are known as the autotrophs.
Example : green plants and blue green algae.
2. Consumers : Those organism which are depend on the producers either directly or indirectly for their food are called consumers. They are known as the heterotrophs.
Example : Animals
The consumers can be classified into the following types :
(i) Herbivores - Those animals which eat only green Plants.
Example Dear, Goats
(ii) Carnivores Those animals which eat only flesh
Example : Lions and tigers.
(iii) Omnivores : Those animals which eat both plants as well as flesh.
Example Humans, bears
(iv) Parasites : Those organisms live on the body of host and take food it without killing them.
Example: leeches and tapworms.
3. Decomposers : Those organisms which feed on dead and decaing living matters are called decomposers.
Or
Those micro organisms which break-down the complex organic substances present in dead remains and waste product of organisms and convert them into simple inorganic substances are called decomposers.
Example: Bacteria and Fungi,
These simple substances go into the soil (land) and are reused by the plants. They act as scavengers in nature
Role of Decomposers
They breakdown the remaing of dead plants and animals and clean up the environment. They act as scavengers in nature
They release nutrients into the soil and helps in natural replenishment of the soil nutrients take place,
They help in recycling of materials in the biosphere.
Food chain
A series of organisms in the ecosystem through which food and energy is transferred from one level to another is called food chain.
Trophic Level : The various step or level in the food chain at which transfer of food (or energy) takes place are called trophic level
A terrestrial food chain:
First trophic level [T₁] - Producers
Second trophic level [T₂] - Primary consumers/Herbivore
Third trophic level [T₃] - Secondary consumers/Carnivore
Fourth trophic level [T₄] - Top consumers/Top Carnivore

Grass ➡ Rat ➡ Snake ➡ Eagle
(Producer) (Herbivore) (Carnivore) (Top Carnivore)

Food Web: A network of interconnected food chains that show relationship between different organisms in an ecosystems is called a food web.

The flow of energy between various components of the environment
1. Energy flow in food chain is always unidirectional because in the food chain the energy moves progressively through various trophic level. i.e. The energy that is captured by the autotrophs does not revert back to the sun and the energy which passes to the herbivores does not come back to autotrophs.
2. The green plants capture about 1% of the energy of sunlight and convert it into chemical energy.
3. At each trophic level only 10% of the energy is passed to the next trophic levell while 90% of energy is either utilized by present trophic level in its life processes or lost in the environment as heat.
4. There is gradual decrease in the amount of energy from one trophic level to next trophic level in a food chain. Due to this gradual decrease in energy, food chains contain 3-4 trophic level.
The loss of energy at each step is so great that very little usable energy remains after four trophic level.
5. There are generally a greater number of organisms at the lower trophic levels of an ecosystem. Hence the greatest number is of the producers.


Ten Percent Energy Law :- According to this rule Only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
Sun 
Producer  Primary consumers  Secondary consumers  Top consumers
100000J ➡     1000J ➡    100J ➡    10J 1J
Significance of Food Chain
(i) It helps in understanding the food relationship and interactions among various organisms in an ecosystem.
(ii) It helps to understand the basic mechanism of transfer of food energy and nutrients through various components of nature.
(iii) It helps to understand the flow of toxic substances in an ecosystem and biological magnification
Biological magnification : The increase in concentration of harmfull chemical substances like pestispesticide in the body of living organism at each trophic level of a food chain is called biological magnification.
The Maximum concentration of these chemicals get accumulated in human bodies. Because human beings occupy the top level in food chain.
These chemicals are not degradable, So these get accumulated progressively at each trophic level
Ozone Layer
Ozone is a molecule formed by three atoms of oxygen. It is a deadly poison.
Ozone layer is largely found in the stratosphere which is a part of our atmosphere
Formation of Ozone
Ozone is formed in the upper atmosphere when solar ultraviolet radiation breaks down oxygen molecules (O₂) to form free oxygen (O) atoms. These free atoms of oxygen react with oxygen (O₂) to form ozone.
O₂ ⟶UV⟶ O + O
O + O₂ ⟶ O₃
(Ozone)
Function of Ozone layer : Ozone protects us from the ultraviolet radiation coming from the Sun.
Depletion of the Ozone Layer
The deplation of ozone layer is due to synthetic chemicals like chlorofluorocarbons (CFCs) which are used in refrigerants and fire extinguishers.
In 1987, the United Nations Environment Program (UNEP) reached an agreement to freeze CFC production to 1986 levels.
Ozone layer can be protected by
Reduce the use of ozone depleting substances. E.g CFC
Prohibit the use of harmful nitrous oxide.
Reduce the use of air conditioner.
Garbage (Waste) Management
The disposal of waste generated by us in such a manner that it doesn't affect our environment adversely is called garbage management
Waste - Waste is defined as unwanted and unusable materials and is regarded as a substance which is of no use. It is of two types.
Biodegradable waste :- The Substance which are broken down in to simpler and harmless substance by the biological process are called biodegradable waste
Example : Domestic waste product and sewage
Non-Biodegradable - The Substance which can not be broken down in to simpler and harmless substance by the biological process are called non-biodegradable waste
These substances are generally 'inert' and accumulate in the environment for a long time or cause harm to the environment.
Example : DDT, Polythene bag erc
Some environment friendly practices which need to be followed are:
1. Separation of biodegradable and non-biodegradable waste should be done to save our resources for future
2.use Clothe bags in palace of plastic bags because they are non-polluting, stronger, more durable and washable.
3. Use of composts and vermicompost in place of fertilizers.
4. Use of Paper cups instead of plastic cups and kulhads because the paper can be recycled it is biodegradable and eco-friendly material

1.      With regard to various food chains operating in an ecosystem, man is a:

[A] Consumer

[B] Producer

[C] Producer and consumer

[D] Producer and decomposer.                                    [A]

2.      Food web is constituted by

[A] relationship between the organisms and the environment

[B] relationship between plants and animals

[C] various interlinked food chains in an ecosystem

[D] relationship between animals and environment. [C]

3.      Which of the following gets the minimum energy through the food chain in an ecosystem?

[A] Herbivores

[B] Carnivorous

[C] Large carnivore

[D] Producers                                                                   [C]

4.      In the food chain, the initial organism is usually:

[A] herbivore

[B] Autotrophs

[C] saprophytic

[D] parasitic                                                                      [B]

5.      In the food chain compromising of snake, grass, insect and frog the secondary consumer is:

[A] grass

[B] snake

[C] frog

[D] insect                                                                         [C]

6.      What will happen if deer is missing in the food chain given: grass  deer  tiger?

[A] The population of tiger decreases and the population of grass increase.

[B] The population of grass decrease.

[C] Tigers will start eating grass.

[D] The population of tiger increase.                           [A]

7.      Flow of energy in an ecosystem is always:

[A] Bidirectional

[B] No specific direction

[C] Unidirectional

[D] Multidirectional                                                      [B]

8.      The ecosystem of earth is known as:

[A] Biosphere

[B] Biomes

[C] Biomagnification

[D] Community                                                              [A]     

9.      The maximum concentration of chemicals get accumulated in:

[A] Human body

[B] Deer

[C] Fishes

[D] Plants                                                                           [A]

10.  In 1987, an agreement was formulated by the United Nations Environment Programme (UNEP) to freeze the production of “X” to prevent depletion of “Y”. “X” and “Y” respectively referred here are:

[A] Ozone; CFCs

[B] CFCs; rays UV

[C] CFCs; Ozone

[D]UV rays; Diatomic oxygen                                      [C]

11.  Which of the following features relates to biodegradable substances?

[A]Broken down by biological processes

[B] Remain inert

[C] Persist in environment for long time

[D] None of above                                                          [A]

12.  May harm the ecosystem Match the following with the correct response:

(1) Biodegradable            (A) Plastics, detergents, Pesticides etc

(2) Non- biodegradable (B) Green plants

(3) Decomposers             (C) Bacteria and Fungi

(4) Producers                   (D) Dead parts of plants and animals

[A] 1-C, 2-B, 3-D, 4-A

[B] 1-D, 2-A, 3-C, 4-B

[C] 1-A, 2-C, 3-B, 4-D

[D]1-B, 2-D, 3-A, 4-C                                                    [B]

13.  Which one of the following is an artificial ecosystem?

[A] Pond

[B] Lake

[C] Forest

[D] Crop field                 [D]

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

Grass — Grasshopper — Frog — Snake — Hawk

[A] 5k

 [B] 50 kJ

[C] 500 kJ

[D] 5000 kj                      [D]

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

[A] eutrophication 

[B] pollution

[C] bio-magpnification

[D] accumulation                       [C]

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

[A] carnivores

[B] herbivores

[C] decomposers

[D] producers                 [A]

17.  An ecosystem includes:

[A] all living organisms

[B] non-living objects

[C] both living organisms and non-living objects

[D] sometimes living organisms and sometimes non-living objects      [C]

18.  In the following groups of materials, which group(s) contain(s) only non-biodegradable items?  (i) Wood, paper, leather  (ii) Polythene, detergent, PVC  (iii) Plastic, detergent, grass  (iv) Plastic, Bakelite, DDT 

[A] (i) and (iii)

[B] (iii) and (iv)

[C] (ii) and (iii)

[D] (i) and (iv) [D] 

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

[A] Decrease in energy at higher trophic  levels

[B] Deficient food supply 

[C] Polluted air 

[D] Water  [A] 

20. Which of the following statements is incorrect?

[A] All green plants and blue-green algae  are producers.

[B] Green plants get their food from organic compounds.

[C] Producers prepare their own food from inorganic compounds.

[D] Plants convert solar energy into chemical energy.. [B]

21.  Which groups 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)

[C] (ii) and (iii)

[D] (i)and (iv)  [C]

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

[A] 1%

[B] 5%

[C] 8%

[D] 10% [A]

23.  The decomposers in an ecosystem: 

[A] convert inorganic material to simpler forms

[B] convert organic material to inorganic forms 

[C] convert inorganic material to organic compounds 

[D] do not breakdown organic compounds  [B] 

24.  If a grasshopper is eaten by a frog, then the energy transfer will be from: 

[A] producer to decomposer 

[B] producer to primary consumer 

[C] primary consumer to secondary consumer 

[D] secondary consumer to primary consumer. [C] 

25.  Disposable plastic plates should not be used because: 

[A] they are made of materials with light weight 

[B] they are made of toxic materials 

[C] they are made of biodegradable materials  [

D] they are made of non-biodegradable materials [D]   

26.  Which of the following are environment-friendly practices?

[A] Carrying cloth-bags to put purchases in while shopping

[B] Switching off unnecessary lights and fans

[C] Walking to school instead of getting your mother to drop you on her scooter

[D] All of the above              [D]

27.  What are the two main components of our environment?

Two main components of our environment are:

a. Biotic (e.g., plants, animals etc.)

b.Abiotic (e.g., soil, air, water etc.)

28.  What is an ecosystem?

An ecosystem is a structural and functional unit of biosphere, in which comprising of all the interacting organism in an area together with the non-living components of the environment

29.  List two man-made ecosystems.

Aquarium, crop land, park are man made ecosystem.

30.  Why is a lake considered to be a natural ecosystem?

Lake is considered as natural ecosystem because Lake has species of plants and animals which are present naturally and interact with each other without human intervention

31.  What is the physical environment of an ecosystem called? Give one example.

Physical environment of an ecosystem is called as the abiotic or non-living component of an ecosystem. This includes physical factors like temperature, rainfall, wind, soil and minerals

32.  We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain.

Ponds or lake is natural ecosystem. In natural ecosystem, decomposers help in recycling waste. So we do not clean ponds or lakes, But an aquarium is a artificial ecosystem. There is no recycling and self cleaning due to absence of the natural decomposers. So an aquarium need to be cleaned regularly.

33.  Why are green plants called ‘producers’ ?

Green plants are called producers because they prepare  their own food in the presence of sunlight and chlorophyll.

34.  Draw a food chain which operates in a forest ecosystem.

➡  ➡ 

Grass  Deer    Tiger.

35.  Make an aquatic food chain up to tertiary consumer level. State the trophic level at which concentration of pesticide is maximum and why?

Phytoplankton Zooplankton Small fish Heron.

Tertiary consumer  Heron.

The Maximum concentration of pesticide get accumulated in Tertiary consumer  Heron. Because Heron occupy the top level in this food chain.

36.  What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.

The various step or level in the food chain at which transfer of food (or energy) takes place are called trophic level
A terrestrial food chain:

     
Grass
Rat Snake Eagle
(Producer) (Herbivore) (Carnivore) (Top Carnivore)

In this food chain

Grass First trophic level [T] - Producers
Rat
Second trophic level [T] - Primary consumers/Herbivore
Snake
Third trophic level [T] - Secondary consumers/Carnivore
Eagle
  Fourth trophic level [T] - Top consumers/Top Carnivore

37.  In the food chain given below identify the trophic level in which the number of organisms available would be minimum?

Grass grasshopper  Frog  Snake  Peacock

Peacock.

38.  Consider a food chain consisting of: wheat, rat, snakes, peacock:

What will happen if all the snakes are killed?

The population of peacocks will decrease and the population of rats will increas.

39.  “Flow of energy is unidirectional.” Name the first two components of the environment involved in this flow of energy from the sun.      

Producers and primary consumers.

40.  State 10 percent law.      

According to this rule Only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.   

41.  A primary consumer in the food chain has 10000 J energy available. How much energy will be provided for tertiary consumer in this food chain?

100 J.

42.  In the following food chain, plants provide 500 J of energy to rats. How much energy will be available to hawks from snakes?

Plants Rats Snakes Hawks

5 J

Plants Rats Snakes Hawks

500J    50J       5J

43.  What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?

1000 joules.

44.  If in t he following food chain, 100 J of energy is available to the lion, how much energy was available to the producer ?

Plants Deer   Lion

10,000 J.

Plants    Deer     Lion

10000 J 1000J 100J

45.  In a food chain of frog, grass, insect and snake, assign trophic level to frog.

In the given food chain, frog belongs to the third trophic level as shown here :

Grass       Insect        Frog       Snake

T          T             T           T

46.  In an ecosystem, rats feed on grains. Name the trophic level to which the rats belong.

Second trophic level.

47.  In a food chain of rabbit , grass and fox, assign t rophic level to rabbit. ?

Grass      Rabbit          Fox

T              T             T  

Rabbit  is a primary consumer or a herbivore or 1st  t rophic level.

48.  The first trophic level in a food chain is always  green plants. Why ?

Only green plants can traps the light energy from the sun and converts it into chemical energy by the process of photosynthesis. So The first t rophic level in a food chain is always  a  green plant.

49.  Which  of  the following  are  always  at  the second trophic level of food chains? Carnivores, Autotrophs, Herbivores.

Herbivores  are  always  at  the second trophic level of food chains       .

50.  Give reason why a food chain cannot have more than four trophic levels.

The loss of energy at each step is so great that very little usable energy remains after four trophic levels.

51.  Write the appropriate names of the trophic levels Z and X in the figure given

Z =Tertiary consumers, X = Primary consumers.

52.  What will happen if we kill all the organisms in one trophic level?

If all the organisms in one trophic level are killed then all the organisms of next trophic level which are dependent on these will not get food to eat and they will die. At the same time the population of organisms at the lower trophic  will increase and the entire food chain gets disturbed.

53.  When plants are eaten by primary consumers, a great deal of energy is lost as heat  to the environment and some amount goes in carrying out various life processes. State the average percentage of energy lost in this manner.

90%.

54.  What is the significance of the food chain?

1. It helps in understanding the food relationship and interactions among various organisms in an ecosystem.

2. It helps to understand the basic mechanism of transfer of food energy and nutrients through various components of nature.

3. It helps to understand the flow of toxic substances in an ecosystem and biological

55.  Name two decomposers operating in our ecosystem.

Bacteria and fungi.

56.  Mention the role of microorganisms like bacteria and fungi in the ecosystem.

1.They breakdown the remaing of dead plants and animals and clean up the environment. They act as scavengers in nature

2.They release nutrients into the soil and helps in natural replenishment of the soil nutrients take place,

3.They help in recycling of materials in the biosphere.

57.  State a way to prevent accumulation of harmful chemicals in our bodies.

To minimize use of pesticides in agriculture.

58.  Why is the maximum concentration of pesticides found in human beings?

The Maximum concentration of pesticides chemicals get accumulated in human bodies. Because human beings occupy the top level in food chain.

59.  The following organisms form a food chain. Which of this will have the highest concentration of non- biodegradable chemicals? Name the phenomenon associated with it .

Insects, Hawk, Grass, Snake, Frog

Grass    Insects    Frog   Snake    Hawk

The Hawk will have the highest concentration of non- biodegradable chemicals and this phenomenon is associated with  Biomagnification

60.  What is meant by biological magnification?

The increase in concentration of harmfull chemical substances like pestispesticide in the body of living organism at each trophic level of a food chain is called biological magnification

61.  In a certain study conducted on occurrence of DDT along food chains in an ecosystem, the concentration of 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?

DDT is non-biodegradable substance which accumulates at each trophic level. Since  human beings occupy the top level in food chain.So there is maximum accumulation of DDT in man

62.  Why are plastics non-biodegradable substances?

Plastics can not be broken down in to simpler and harmless substance by the biological process.

63.  What  is  meant  ‘non-biodegradable’  waste?  Identify biodegradable waste from the following:

Empty packet of chips, empty plastic bott le of mineral water, empty paper box of sweets, empty tin of a cold drink.

The Substance which can not be broken down in to simpler and harmless substance by the biological process are called non-biodegradable waste 

Empty paper box of sweets is biodegradable wastef

64.  DDT was sprayed in a lake to regulate breeding of mosquitoes. How would it affect the trophic levels in the following food chain associated with a lake? Justify your answer.

DDT being a non- biodegradable pesticide will enter the food chain from the first trophic level i.e Plankton.

Non – biodegradable pesticides accumulate progressively at each trophic level. This phenomenon is known as biological magnification.

The Hawk will have the highest concentration of  DDT because Hawk occupy the top level in food chain..

65.  How does concent ration of a pesticide change once it enters a food chain?         

Concentration of pesticide gets accumulated progressively at each trophic level once it enters a food chain.

66.  Pesticides like DDT which are sprayed to kill pests on crops are found to be present in the soil, groundwat er, water bodies et c. Explain how do they reach these places?

Soil: Pesticides are sprayed to protect plants from diseases and pests.These chemicals are washed down in to the soil and get settled into soil particles.

Groundwater: Through irrigation in the fields, these pesticides present in soil pass into lower layers of soil and reaches groundwater.

Water bodies: These chemicals are washed down into the water bodies.The agricultural waste affected from pesticides is thrown in water bodies Thus they reach in the water bodies

67.  Why are non-biodegradable subst ances not broken down by microbes?

Microbes are highly specific enzymes which can only breakdown natural  materials.

68.  Mention one negative effect of our affluent lifestyle on the environment.

One negative effect of our affluent lifestyle on the environment is  pollute the environment.

69.  Give the full name of  UNEP

United Nations Environment Programme.

70.  What is ozone ?

Ozone is a molecule formed by three atoms of oxygen. It is a deadly poison.

71.  Name the rays against which ozone layer provides protection.

Ultraviolet radiation

72.  What is the function of ozone in the upper atmosphere?

Ozone protects us from the ultraviolet radiation coming from the Sun

73.  Why should use of Chlorofluorocarbons be reduced?

Chlorofluorocarbons [CFCs] are responsible for depletion of ozone layer.

74.  Write the full name of the group of compounds mainly responsible for the depletion of ozone layer or Give the full form of CFC.

Chlorofluorocarbon

75.  Ozone is deadly poisonous, still it performs an essent ial funct ion. How?

Ozone protects us from the ultraviolet radiation coming from the Sun.

76.  Why is the ozone layer getting depleted at the higher levels of the atmosphere?

Ozone is present at higher levels of the atmosphere where the chlorine separates from CFC in sutable conditions and splits O3 into O2 and (O).

77.  How is ozone formed in the upper atmosphere?

Ozone is formed in the upper atmosphere when solar ultraviolet radiation breaks down oxygen molecules (O) to form free oxygen (O) atoms. These free atoms of oxygen react with oxygen (O) to form ozone.

O UV O + O

O + O O

            (Ozone)

78.  Which compounds are responsible for the deplet ion of ozone layer?

1. Chlorofluorocarbons (CFCs) which are used as refrigerants

2. Halons

3. CCl4 Carbon tetrachloride.

79.  Ozone formation takes place in the stratosphere of our atmosphere.

(a) Explain how the energy of the Sun helps in the formation of ozone.

High energy UV radiation from the Sun breaks apart some of the molecular oxygen into free oxygen. The free oxygen then combines with the remaining molecular oxygen to form ozone.

(b) Why is ozone formation at ground level considered a pollutant?

Ozone is deadly to humans at lower levels of the atmosphere

(c) State any two health consequences of ozone layer depletion on human health.

1. Skin cancer

2. Cataract

80.  Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Ozone protects us from the ultraviolet radiation coming from the Sun. In absence of ozone layer heavy damage to organism may occur. It may cause diseases like skin cancer, cataract  etc.

Ozone layer can be protected by

Reduce the use of ozone depleting substances. E.g CFC

Prohibit the use of harmful nitrous oxide.

Reduce the use of air conditioner

81.  Select one item which is made up of biodegradable material - plastic bag, leather bag, nylon rope, kettle ?

Leather bag.

82.  Distinguish between biodegradable and non- biodegradable substances

Biodegradable waste :-

1. The Substance which are broken down by the biological process are called biodegradable waste

Example : Domestic waste product and sewage

2. These subsances are environment friendly.

3. These substances get recycled and therefore, do not require any dumping sites

Non-Biodegradable -

1. The Substance which can not be broken down by the biological process are called non-biodegradable waste

Example Plastic bag,metal, Glass

2.These subsances are harmful to the environment and causes pollution.

3. These substances require a lot of space for dumping which causes wastage of land

83.  Why some materials are biodegradable whereas others are non-biodegradable ?

The micro-organisms like bacteria and other decomposer organisms present in our environment are 'specific' in their action. They break down the natural materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable whereas others are non-biodegradable.

84.  How do bacteria and fungi able to decompose some of the wastes in our ecosystem?

Bacteria and fungi  are 'specific' in their action. They have enzymes to break down the  complex organic substances and convert them into simple inorganic substances

85.  Give any two ways in which non-biodegradable substances would affect the environment.

(i) The non-biodegradable substances get accumulated and doesn’t get decomposed hence it remains in the ecosystem and causes pollution, chokes the system of many animals and kill them.

(ii) Some of the non-biodegradable pesticides enter the food chain and cause biomagnification

86.  Give any two ways in which bio-degradable substances would affect the environment.

(i) During decomposition of thebio-degradable substances lot of foul smell spreads in the surrounding areas.

(ii) The place where these bio-degradable substance are present with some moisture becomes breeding ground for insects like mosquitoes, housefly

87.  “Improvements in our lifestyle have resulted in greater amounts of waste generation.” Give two examples to support the given statement. Suggest one change that we can incorporate in our lifestyle in order to reduce non-biodegradable waste.

1. More use of dispossible items like paper plates, plastic items, polythene etc.

2. Changes in packaging

Suggestion – Reuse of polythene bages, plastic containers.

88.  “Human beings occupy the top level in any food chain.” What are the consequences of this on our body?

1. Maximum level of bio magnification occurs here because of progressive accumulation.

2. We get very small amount of energy as only 10 % of the previous energy gets transferred at each trophic level

89.  Suggest one word for each of the following statement/definitions: 

(i) The physical and biological world where we live.  Ecosystem

(ii) Each level of food chain where transfer of energy takes place.  Trophic level

(iii) The physical factors like temperature, rainfall, wind and soil of an ecosystem.  Abiotic factors

(iv) Organisms which depend on the producers either directly or indirectly for food. Consumers:

90.  State two methods to get rid of non-biodegradable wastes.

(a) Paper bags or cloth bags should be used to carry things instead of plastic bags.

(b) Non-biodegradable waste should be collected separately and sent for recycling.

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

(i)  Cloth bags are more durable and thus can be used again and again 

(ii)They are strong and thus capable of carrying more things. 

(iii)They are biodegradable in nature

92.  Accumulat ion of harmful chemicals in our body can be avoided. Explain how this can be achieved.

a. Washing vegetables and fruits properly with water.

b. Soak vegetables and fruits in salt water for few minutes before  cooking.

c.‘Organic subtances’ should be used for cultivation.

93.  How can you help in reducing the problem of waste disposal? Give any two methods.

(a) Recycling the non-biodegradable waste material.

(b) Preparation of compost.

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

Energy flow in food chain is always unidirectional because in the food chain the energy moves progressively through various trophic level. i.e. The energy that is captured by the autotrophs does not revert back to the sun and the energy which passes to the herbivores does not come back to autotrophs.

The flow of energy  among various components of the environment is as follows

Sun Producer Primary Consumer autotrophs

95.  If all the waste we generate is biodegradable, will this have no impact on the environment?

The action of decomposers will slow down So the wastes cannot decompose into harmless simpler substance at the right time. Due to this it will become a breeding ground for flies causing the spread of diseases

The rotting biodegradable wastes emit foul smell in the environment which makes the life of people miserable.

96.  Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

The impact of removing all organisms in a trophic level will be different for different trophic levels.

For example, in the food chain : Grass Deer Lion : 

(i) If we remove all the lions at the third trophic level, then the number of deer will increase too much. All these deer will eat up all the grass and other plants turning the forest into a desert. 

(ii) If we remove all the deer at the second trophic level, then lions will not get sufficient food, they will starve and die. Deer eat grass and other green plants, so the amount of grass and other green plants will increase too much.

No, all the organisms of any trophic level cannot be removed without causing any damage to the ecosystem.

97.  In the food chain (Grass Deer Lion) operating in a forest, what will happen if all

(a) Lions are remove

If all the lions are removed from the above food chain, the population of deer will increase greatly and they will eat the whole grass. The density of grass will be very much reduced and this will turn the area into a desert.

(b) Deer are remove

If all deers are removed from the given food chain, then

a.   Tigers will not survive.

b.   Plants will increase in number.

 

 

 


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