Text Book Back Questions and Answers - Chapter 7 Ecosystem 12th Biology Botany Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Ecosystem
Text Book Back Questions and Answers
Question 1.
Which of the following is not a abiotic component of the ecosystem?
(a) Bacteria
(b) Humus
(c) Organic compounds
(d) Inorganic compounds
Answer:
(b) Humus
Question 2.
Which of the following is / are not a natural ecosystem?
(a) Forest ecosystem
(b) Rice field
(c) Grassland ecosystem
(d) Desert ecosystem Pond is a type
Answer:
(b) Rice field
Question 3.
Pond is a type of
(a) Forest ecosystem
(b) grassland ecosystem
(c) marine ecosystem
(d) fresh water ecosystem Pond ecosystem
Answer:
(d) fresh water ecosystem Pond ecosystem

Question 4.
Pond ecosystem is
(a) not self sufficient and self regulating
(b) partially self sufficient and self regulating
(c) self sufficient and not self regulating
(d) self sufficient and self regulating
Answer:
(d) self sufficient and self regulating
Question 5.
Profundal zone is predominated by heterotrophs in a pond ecosystem, because of
(a) with effective light penetration
(b) no effective light penetration
(c) complete absence of light
(d) a and $b$
Answer:
(d) a and $b$
Question 6.
Solar energy used by green plants for photosynthesis is only
(a) $2-8 \%$
(b) $2-10 \%$
(c) $3-10 \%$
(d) $2-9 \%$
Answer:
(b) $2-10 \%$
Question 7.
Which of the following ecosystem has the highest primary productivity?
(a) Pond ecosystem
(b) Lake ecosystem
(c) Grassland ecosystem
(d) Forest ecosystem
Answer:
(c) Grassland ecosystem

Question 8.
Ecosystem consists of
(a) decomposers
(b) producers
(c) consumers
(d) all of the above
Answer:
(d) all of the above
Question 9.
Which one is in descending order of a food chain?
(a) Producers $\rightarrow$ Secondary consumers $\rightarrow$ Primary consumers $\rightarrow$ Tertiary consumers
(b) Tertiary consumers $\rightarrow$ Primary consumers $\rightarrow$ Secondary consumers $\rightarrow$ Producers
(c) Tertiary consumers $\rightarrow$ Secondary consumers $\rightarrow$ Primary consumers $\rightarrow$ Producers
(d) Tertiary consumers $\rightarrow$ Producers $\rightarrow$ Primary consumers $\rightarrow$ Secondary consumers
Significance of food web is / are
Answer:
(c) Tertiary consumers $\rightarrow$ Secondary consumers $\rightarrow$ Primary consumers $\rightarrow$ Producers
Question 10.
Significance of food web is / are
(a) it does not maintain stability in nature
(b) it shows patterns of energy transfer
(c) it explains species interaction
(d) b and c
Answer:
(d) b and c
Question 11.
The following diagram represents

(a) pyramid of number in a grassland ecosystem
(b) pyramid of number in a pond ecosystem
(c) pyramid of number in a forest ecosystem
(d) pyramid of biomass in a pond ecosystem
Answer:
(c) pyramid of number in a forest ecosystem
Question 12.
Which of the following is / are not the mechanism of decomposition?
(a) Eluviation
(b) Catabolism
(c) Anabolism
(d) Fragmentation
Answer:
(c) Anabolism
Question 13.
Which of the following is not a sedimentary cycle?
(a) Nitrogen cycle
(b) Phosphorous cycle
(c) Sulphur cycle
(d) Calcium cycle
Answer:
(a) Nitrogen cycle
Question 14.
Which of the following are not regulating services of ecosystem services?
(i) Genetic resources
(ii) Recreation and aesthetic values
(iii) Invasion resistance
(iv) Climatic regulation
(a) i and iii
(b) ii and iv
(c) $\mathrm{i}$ and ii
(d) $i$ and iv
Answer:

(c) i and ii
Question 15.
Productivity of profundal zone will be low. Why?
Answer:
The producers of the pond ecosystem depends on phytoplankton through photosynthesis.
Profundal zone lies below the limnetic zone with no effective light penetration, hence productivity rate is very low.
Question 16.
Discuss the gross primary productivity is more efficient than net primary productivity.
Answer:
Gross primary productivity:
1. It refers to the total amount of food energy or organic matter produced in an ecosystem by autotrophs.
2. $\mathrm{GPP}=\mathrm{NPP}+$ Respiration
Net primary productivity:
1. It refers to the amount of energy that remain in autotrophs after respiration loss.
2. $\mathrm{NPP}=\mathrm{GPP}-$ Respiration
Question 17.
Pyramid of energy is always upright. Give reasons.
Answer:
The energy pyramid represents a successive energy flow at each trophic level in an ecosystem. There is a gradual decrease in energy transfer at successive tropic levels from producers to higher levels, hence the pyramid of energy is always upright.
Question 18.
What will happen if all producers are removed from ecosystem?
Answer:
Producers are the autotrophs which occupy the first tropic level in an ecosystem. The energy produced by them is utilized by the herbivores and then by carnivores, thereby maintaining the stability of ecosystem. If producers are removed from an ecosystem, it would lead to starvation and death of herbivores and subsequently the carnivores, thus terminating the entire food web.

Question 19.
Construct the food chain with the following data.
Hawk, plants, frog, snake, grasshopper.
Answer:
Plants $\rightarrow$ Grasshopper $\rightarrow$ Frog $\rightarrow$ Snake $\rightarrow$ Hawk
Question 20.
Name of the food chain which is generally present in all type of ecosystem. Explain and write their significance.
Answer:
Detritus food chain is common in all type of ecosystem. In detritus food chain, the dead remains of plant and animals or their excreta are broken down by detrivores and the organic and inorganic substances are returned back to environment. Thus maintaining die company of various biogeochemical cycles. Also Microbes growing on detritus makes the soil nutritious for consumers.
Question 21.
Shape of pyramid in a particular ecosystem is always different in shape. Explain with example.
Answer:
In a forest ecosystem the pyramid of number is spindle in shape, it is because the base $\left(T_1\right)$ of the pyramid occupies large sized trees (Producer) which are lesser in number. Herbivores $\left(\mathrm{T}_2\right.$ ) (Fruit eating birds, elephant and deer) occupying second trophic level, are more in number
than the producers. In final trophic level $\left(\mathrm{T}_4\right)$, .tertiary consumers (lion) are lesser in number than the secondary consumer $\left(T_3\right)$ (fox and snake).
Question 22.
Generally human activities are against to the ecosystem, where as you a student how will you help to protect ecosystem?
Answer:
1. Buying and using only ecoffiendly products and recycle them.
2. Growing more trees.
3. Choosing sustained farm products (vegetables, fruits and greens, etc.)
4. Reducing the use of natural resources.

5. Recycling the waste and reduce the amount of waste you produce.
6. Reducing consumption of water and electricity.
7. Reducing or eliminating the use of house-hold chemicals and pesticides.
8. Maintaining your cars and vehicles properly to reduce carbon emission.
9. Creating awareness and educate about ecosystem protection among your friends and family members and ask them to find out solution to minimise this problem.
Question 23.
Generally in summer the forest are affected by natural fire. Over a period of time it recovers itself by the process of successions. Find out the types of succession and explain. Secondary succession.
Answer:
The development of a plant community in an area where an already developed community has been destroyed by natural causes is known as secondary succession. This type of succession takes less time to occur.
Question 24.
Draw a pyramid from following details and explain in brief.
Answer:
Quantities of organisms are given-Hawks-50, plants-1000, rabbit and mouse-250 +250 , pythons and lizard $-100+50$ respectively

$
\mathrm{T}_4(50) \mathrm{T}_3(100) \mathrm{T}_2(550) \mathrm{T}_1(1000)
$
The pyramid produced is an upright pyramid of numbers where there is a gradual decrease in number of organisms at each trophic level from $T_1$ to $T_4$. This is an example for grassland ecosystem.
Question 25.
Various stages of succession are given bellow. From that rearrange them accordingly. Find out the type of succession and explain in detail.
Answer:
Reed-swamp stage, phytoplankton stage, shrub stage, submerged plant stage, forest stage, submergedfree floating stage and marsh medow stage.
(1) Phytoplankton stage - It is the first stage of succession consisting of the pioneer community like blue green algae, green algae, diatoms, bacteria, etc., The colonization of these organisms enrich the amount of organic matter and nutrients of pond due to their life activities and death. This favors the development of the next serai stages.
(2) Submerged plant stage - As the result of death and decomposition of planktons, silt brought from land by rain water, lead to a loose mud formation at the bottom of the pond. Hence, the rooted submerged hydrophytes begin to appear on the new substratum. Example: Vallisneria and Hydrilla etc. The death and decay of these plants will build up the substratum of pond to become shallow.
(3) Submerged free floating stage - During this stage, the depth of the pond will become almost 2-5 feet Hence, the rooted hydrophytic plants and with floating large leaves start colonising the pond.
Example: Rooted floating plants like Nelumbo, Nymphaea and some free floating species like Azolla, and Pistia are also present in this stage. By death and decomposition of these plants, further the pond becomes more shallow.

(4) Reed-swamp stage - It is also called an amphibious stage. During this stage, rooted floating plants are replaced by plants which can live successfully in aquatic as well as aerial environment.
Example: Typha, Phragmites, Sagittaria and Scirpus etc. At the end of this stage, water level is very much reduced, making it unsuitable for the continuous growth of amphibious plants.
(5) Marsh meadow stage - When the pond becomes swallowed due to decreasing water level, species of Cyperaceae and Poaceae colonise the area. They form a mat-like vegetation with the help of their much branched root system. This leads to an absorption and loss of large quantity of water. At the end of this stage, the soil becomes dry and the marshy vegetation disappears gradually and leads to shurb stage.
(6) Shrub stage - Here areas are invaded by terrestrial plants like shrubs (Salix and Comus) and trees (Populus and Alnus). These plants absorb large quantity of water and make the habitat dry. Further, the accumulation of humus with a rich flora of microorganisms produce minerals in the soil, ultimately favouring the arrival of new tree species in the area.
(7) Forest stage - It is the climax community of hydrosere. A variety of trees invade the area and develop any one of the diverse type of vegetation.
Example.Temperate mixed forest (Ulmus,Acer and Quercus), Tropical rain forest (Artocaipus and Cinnamomum ) and Tropical deciduous forest (Bamboo and Tectona).