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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.
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
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 [T₁] - Producers
Rat ➡ Second trophic level [T₂] - Primary consumers/Herbivore
Snake ➡Third trophic level [T₃] - Secondary consumers/Carnivore
Eagle ➡ Fourth
trophic level [T₄] - 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
T₁ → T₂ → T₃ → T₄
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
T₁ → T₂ → T₃
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
(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)
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.
