Class 9 science and technology chapter 7 energy flow in an ecosystem question answer
Class 9 science and technology chapter 7 question answer Energy Flow In an Ecosystem | Energy Flow In an Ecosystem class 9 exercise answers Maharashtra board | Energy Flow In an Ecosystem 9 solution state board.
Q.1. Complete the following table (Carefully study the carbon, oxygen and nitrogen cycles).
|
Bio-geo-chemical
cycles |
Biotic processes |
Abiotic
processes |
|
1. Carbon
cycle |
Photosynthesis
and repiration, decomposition by decomposers. |
Combustion
Absorption by water |
|
2. Oxygen
cycle |
Photosynthesis
and respriration, decomposition by decomposers |
Combustion,
production of ozone and oxides |
|
3. Nitrogen
cycle |
Industrial
fixation, physical fixation, Nitrification, Denittrification |
|
Q.2. Correct and rewrite the following statements and justify your corrections.
a. Carnivores occupy the second trophic level in the food chain.
Answer:
Correction: Carnivores occupy the third
trophic level. Autotrophic producers constitute the first trophic level.
Herbivorous animals obtain their nutrients from them. They occupy second
trophic level. Carnivorous animals feed upon these herbivorous animals,
therefore, they occupy the third trophic level in the food chain.
b. The flow of nutrients in an ecosystem is considered to be a ‘one way’ transport.
Answer:
Correction: The flow of nutrients in an
ecosystem is considered to be cyclic . The green plants are producers. By
photosynthesis they convert minerals and inorganic compounds into glucose. This
food is transfered along with food chain from producers→ primary consumers → secondary consumers. The decomposers of the
ecosystem decompose all the dead and decaying organisms and return these
nutrients back to the ecosystem. Thus, the flow of nutrients is cyclic and not
one way transport
c. Plants in an ecosystem are called primary consumers.
Answer:
Correction: Plants in an ecosystem are
producers. Green plants are called producers as they carry out photosynthesis
with the help of solar energy. The food which they produce is utilized by the
herbivores. Therefore, they are called producers. Herbivores are primary
consumers.
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3. Give reasons.
a. Energy flow through an ecosystem is ‘one way’.
Answer:
(1) Sun is ultimate source of energy.
(2) In all ecosystems, producers (green
plants) store the solar energy in the form of food .
(3) This energy is passed on from one trophic
level to the other trophic level.
(4) Owing to decomposition some part of this
energy is released in the form of heat.
(5) However no part of energy returns to the
sun. Therefore, energy flow through an ecosystem is one way.
b. Equilibrium is necessary in the various bio-geo-chemical cycles.
Answer:
(1) In nature, the various bio – geochemical
cycles operate simultaneously and there is an equilibrium between them.
(2) During these cycles, the inorganic
compounds that are released from organic compounds are released back to nature.
(3) Soil bacteria and other decomposers play
a vital role in these cycles.
(4) If bio – geochemical cycles are
imbalanced then they bring about the imbalance in the ecosystem as a result of
which the ecosystem is destroyed. This shows that equilibrium is necessary in
the various bio – geochemical cycles.
c. Flow of nutrients through an ecosystem is cyclic.
Answer:
(1) Producers obtain nutrients from the soil
, and CO₂ from the atmosphere and synthesise food from them with the help of
photosynthesis .
(2)
During this process, the inorganic substances are converted into organic
substances .
(3) Consumers consume the food produced by
producers. The energy in the form of food is thus passed on from one trophic
level to the other trophic level.
(4) Both producers and consumers after their
and after decomposition the nutrients released from them mix with the soil. In
the same way, the excreta of animals undergo decomposition and release
nutrients to the environments.
Thus, we see that the flow of nutrients in
the ecosystem follows a cyclic path.
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4. Explain the following cycles in your own words with suitable diagrams.
a. Carbon cycle.
Answer:
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Carbon Cycle
b. Nitrogen cycle.
Answer:
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Nitrogen Cycle
c. Oxygen cycle
Answer:
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Oxygen Cycle
5. What would you do to help maintain the equilibrium in the various bio-geo- -chemical cycles? Explain in brief.
Answer:
For maintaining the balance in the bio
geochemical cycles, following measures have to be taken :
(1) We have to conserve plants like trees,
creepers and the entire available flora. For this, we have to at once stop
felling of the trees. If plants are destroyed, the productivity of the
ecosystem is hampered. Therefore the flora has to be well maintained.
(2) We should not kill and poach carnivorous
wild animals. This results in disturbance in the ecological balance. In order
to protect the equilibrium we should conserve the food chains.
(3) Under any condition, apex consumer should
not be killed. The hunting makes the valuable species to become extinct.
Moreover, the population of herbivorous animals will not be under control if
carnivores are killed. By exterminating the apex consumers, the
interrelationships between food chains and food web will suffer.
(4) Anthropogenic activities such as
pollution, deforestation, constructions in the wild habitat, over consumption
of natural resources should be immediately kept under control .
6. Explain in detail the inter-relationship between the food chain and food web.
Answer:
(1) In every ecosystem , interaction go on
continuously between producers , consumers and saprophytes .
(2) These interactions follow a definite sequence called the food chain .
(3) Each food chain consists of four, five or
more links.
(4) An ecosystem consisting of interconnected
food chains at various levels constitute a food web. e.g. Insects ( Primary consumer
) nibble grass ( Producer ) . Frogs (Secondary consumer) feed on insects. This
is a straight food chain. Insects are also eaten by sparrow. Sparrow becomes
food for owl. Owl also kills snakes. Snakes (Tertiary consumer) feed on frogs.
Apex carnivore, hawk, feeds on sparrow, snake or frog too. In this way, smaller
food chains are interconnected in a web form constituting the food web.
(5) Thus, there is an interrelationship
between the food chain and food web.
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7. State the different types of bio-geochemical cycles and explain the importance of those cycles.
Answer:
(1) The bio – geochemical cycles are of two
types, viz. gaseous cycle and sedimentary cycle.
(2) The cyclic gaseous cycle includes
transformation of carbon dioxide , oxygen , nitrogen , water vapour , etc.
while sedimentary cycle includes cyclic movement of calcium , phosphorus , iron
, etc. that are present in soil .
(3) In an ecosystem, producers produce food
by making use of solar energy. While doing so, they absorb nutrients from soil,
air and water. In gaseous bio – geochemical cycle, the nutrients are in air
while in sedimentary cycles they are in soil.
(4) Consumers that feed on producers also
pass nutrients to their bodies .
8. Explain the following with suitable examples.
a. What type of changes occur in the amount of energy during its transfer from plants to apex consumers?
Answer:
(1) Green plants of the ecosystem store large
amount of energy in the form of carbohydrates and proteins.
(2) Before reaching the decomposers, this
energy is passed through different trophic levels like primary consumer,
secondary consumer, tertiary consumer, etc.
(3) The level of energy goes on decreasing
while moving through one trophic level to the other because some amount of
energy is liberated in the form of heat.
(4) The apex consumer receives the least
amount of energy.
b. What are the differences between flow of matter and of energy in an ecosystem? Why?
Answer:
|
Energy flow in an ecosystem |
Flow of nutrients in an ecosystem |
|
1.Flow
of energy in an ecosystem is unidirectional. |
1.Flow
of nutrients in an ecosystem is cyclic |
|
2.The
energy from producers to consumers is passed from one trophic level to the
other trophic level. |
2.Nutrients
from producers is passed from primary consumers and from primary consumers to
secondary consumers. Only decomposers make the nutrients available in a
cyclic way. |
|
3.Some
part of enegy which is not utilized is thrown into the atmosphere. |
3.Nutrients
are not destroyed into the ecosystem. Share
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