Top 100+ Ecosystem - Biology Questions and Answers For NEET 2024 Exam Preparation

Q1. Secondary succession takes place on/in

1. bare rock
2. newly cooled lava
3. newly created pond
4. degraded forest

Answer: (d)

Secondary succession (subsere) is the biotic succession that occurs in an area which become secondarily bare due to the destruction of community previously present there. Secondary succession starts from previously built up substrata with already existing living matter. The action of any external force, such as a sudden change in climatic factors, biotic intervention, fire, etc., had resulted in the destruction of previous community.

Thus, area became devoid of living matter but its substratum, is built up. It has organic matter, so is biologically fertile and thus the successions are comparatively more rapid.

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Q2. Which is the reason for highest biomass in aquatic ecosystem?

1. Benthic and brown algae
2. Sea grass and slime moulds
3. Nano plankton, blue green algae and green algae
4. Diatoms

Answer: (a)

The benthic region includes all the sea floor from the wave-washed shore-line to the greatest depths. Depending upon the penetration of light it is subdivided into two main zones : the lighted or littoral zone and the deep sea system. Due to abundance of light, water, oxygen, carbon dioxide and less salinity of water, the tidal zone is characterized by exhorbitant growth of plants.

The dense growth of vegetation, on the other hand, provides shelter and food for animals. A wide variety of algae, few grasses and animals of every phylum of animal kingdom are represented in this region.

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Q3. Natural reservoir of phosphorus is :

1. Rock
2. Animal bones
3. Fossils
4. Sea water

Answer: (a)

The natural reservoir of phosphate is rock which contains phosphorus in the form of phosphates when rocks are weathered, minute amounts of these phosphate dissolve in soil solution and are absorbed by the roots of the plants . Herbivores and other animals obtain this element from plants.

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Q4. Which of the following organisms in the given food web (in below figure) acts as a primary consumer?

1. I, II and III
2. II, IV and V
3. II, III and IV
4. IV, VII and VIII

Answer: (b)

Animals, which feed directly on plants, i.e. herbivores are primary consumers (grasshopper, rabbit and mouse).

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Q5. Energy storage at consumer level is called

1. secondary productivity
2. gross primary productivity
3. net primary productivity
4. net productivity

Answer: (a)

Secondary productivity is the rate of storage of organic matter by consumers per unit area per unit time.

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Q6. Read the following statements.

1. Decomposers are heterotrophs.
2. Detritus food chain and decomposers are related with each other.
3. The natural water connection of food levels forms food chain.
4. Decomposers are also called as consumers.

Which of the statements given above are correct?

1. I and III are true, II and IV are false
2. I and II are true, III and IV are false
3. III and IV are true, I and II are false
4. All statements are true

Answer: (b)

Statements I and II are true and statements III and IV are false. Statements III and IV can be corrected as

• The natural water connection of food levels does not form food chain. Food chain is the sequence of species or organisms through which the food energy (not water) pass in a community.
• Decomposers are also called saprotrophs.

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Q7. If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following chain?

Plant → Mice → Snake → Peacock

1. 0.002 J
2. 0.02 J
3. 0.2 J
4. 0.0002 J

Answer: (b)

Herbivores are eaten by primary carnivores. Only 10% of the herbivores productivity is utilized for raising productivity of primary carnivores. The rest is consumed in ingestion, respiration, maintenance of body heat and other activities.

Higher carnivores similarly are able to retain only 10% of energy present in primary carnivores. It is called 10% law which was proposed by Lindemann. Accordingly, if plant trapped 20 J of energy, mice will have 2 J, snake will have 0.2 J and hence, peacock will have 0.02 J of energy.

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Q8. If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following food chain?

Plant → Mice → Snake → Peacock

1. 0.002 J
2. 0.02 J
3. 0.2 J
4. 0.0002 J

Answer: (b)

According to 10% law of energy flow, peacock will receive 0.02 J of energy as top consumer. Energy received by the organisms at different trophic level can be seen as follows

Plant → 20J

Mice → 20 × 10 % = 2J

Snake → 2 × 10 % = 0.2 J

Peacock → 0.2 × 10 % = 0.023J

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Q9. Food chain in which microorganisms breakdown the food formed by primary producers is

1. consumer food chain
2. detritus food chain
3. parasitic food chain
4. predator food chain

Answer: (b)

The dead organic matter of plants or animals is called as detritus. While a part of it remains on the soil surface as litter, the other part enters the soil. Many animals such as protozoans, nematodes, insects, etc., depend on detritus and hence they are called as detritivores.

Even the human beings are detritivores when they eat cooked food. From detritus, the chain proceeds to detritivores, then to carnivores and finally to top carnivores.

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Q10. Find the incorrect statement.

1. In aquatic ecosystem a major conduit for energy flow is GFC.
2. In terrestrial ecosystem larger fraction of energy flow occurs through DFC.
3. Detritus food chain is not at all connected with grazing food chain at any level.
4. Natural interconnection of food chain makes it a food web.

Answer: (c)

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Q11. Suppose 2000 J of solar energy is incident on green vegetation. On the basis of 10% law of Lindemann. Identify A, B and C.

1. A – 200 J, B – 20 J, C – 2 J
2. A – 20 J, B – 2 J, C – 0.2 J
3. A – 400 J, B – 40 J, C – 4 J
4. A – 40 J, B – 4 J, C – 0.4 J

Answer: (b)

Only about 10% is stored at higher trophic level and the remaining 90% is lost in respiration, decomposition and waste in the form of heat. Suppose 2000 J of solar energy is incident on green vegetation. The latter having about 1% efficiency, trap about 20 J of energy and convert it into chemical energy by photosynthesis.

The remaining would be lost to the environment. The herbivore that feeds on producers get 10% of the energy stored in plants, i.e. 2 J. The remaining 18 J are lost to the environment. Carnivores feeding on herbivores would be able to store only 0.2 J of energy as flow.

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Q12. Identify the likely organisms (a), (b), (c) and (d) in the food web shown below:

1. A: Rat, B: Dog, C: Tortoise, D: Crow
2. A: Dog, B: Squirrel, C: Bat, D: Deer
3. A: Squirrel, B: Cat, C: Rat, D: Pigeon
4. A: Deer, B: Rabbit, C: Frog, D: Rat

Answer: (d)

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Q13. Which one is nature's cleaner ?

1. Decomposers and scavengers
2. Producers
3. Consumers
4. Symbionts

Answer: (a)

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Q14. The zone at the edge of a lake or ocean which is alternatively exposed to air and immersed in water is called

1. benthic zone
2. pelagic zone
3. lentic zone
4. littoral zone

Answer: (d)

The littoral zone is the zone at the edge of a lake or ocean or in aquatic habitat which is alternatively exposed to air and immersed in water. This costal zone is rich in producers from surface to bottom, with a large number of brown and red algae.

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Q15. Which of the following pairs is a sedimentary type of biogeochemical cycle?

1. Phosphorus and nitrogen
2. Phosphorus and sulphur
3. Oxygen and nitrogen
4. Phosphorus and carbon dioxide

Answer: (b)

Biogeochemical cycles : Two types :

(i) Gaseous : Biogenetic materials involved in circulation are gases e.g. $N_2 , O_2 , CO_2$ etc.

(ii) Sedimentary : Biogenetic materials involved in circulation are non-gaseous eg. P, Ca, S etc. form rocks.

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Q16. The second stage of hydrosere is occupied by plants like

1. Typha
2. Azolla
3. Salix
4. Vallisneria.

Answer: (d)

Series of biotic communities that develop one after the other in a newly formed pond or lake is called hydrosere. It starts as soon as the muddy water becomes clear. The pioneer stage of hydrosere is plankton stage.

Death and decomposition of planktons in the first seral stage of hydrosere produces organic matter which mixes up with clay and silt at the bottom to form soft mud which is favourable for growth of submerged hydrophytes in the next seral stage. Hence, the second stage of hydrosere is occupied by submerged hydrophytes like Vallisneria.

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Q17. Which of the following organisms in the given food web act as a secondary consumer?

1. V and VI
2. I and IV
3. III and VI
4. IV and VII

Answer: (c)

Secondary consumers are those which feed on primary consumers, i.e. lizard and snake here.

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Q18. An ecosystem is a

1. group of interacting species in one place at one time.
2. group of components that interact with one another.
3. biological community and component of the physical environment with which the community interacts.
4. group of interacting chemicals and their cycles.

Answer: (c)

Any unit which includes all the organisms interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity & material cycle within the system is called ecosystem.

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Q19. Which of the following ecological pyramids is generally inverted?

1. Pyramid of biomass in a forest
2. Pyramid of energy
3. Pyramid of biomass in a sea
4. Pyramid of numbers in grassland

Answer: (c)

Pyramid of biomass in sea is generally inverted because the biomass of a trophic level depends upon reproductive potential and longevity of its members. In a sea, the biomass of phytoplanktons is usually lesser than that of zooplanktons, while the biomass of carnivores is greater than small carnivores and zooplanktons. On the other hand, pyramid of energy is always upright. Pyramid of biomass in terrestrial ecosystems (forests, grasslands) is also upright.

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Q20. In a balanced ecosystem you would expect the biomass of the ......... to be greater than the biomass of any other groups of organisms. The most appropriate word to fill the blank is

1. primary consumers
2. producer
3. secondary consumers
4. top predators

Answer: (b)

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Q21. Secondary succession takes place on/in

1. Degraded forest
2. Bare rock
3. Newly created pond
4. Newly cooled lava

Answer: (a)

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Q22. Which is a pioneer species in primary succession on rocks?

1. Lichens
2. Algae
3. Bryophyte
4. Pteridophyte

Answer: (a)

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Q23. What type of ecological pyramid would be obtained with the following data?

Secondary consumer : 120 g Primary consumer : 60 g Primary producer : 10 g

1. Pyramid of energy
2. Upright pyramid of numbers
3. Inverted pyramid of biomass
4. Upright pyramid of biomass

Answer: (c)

An inverted pyramid of biomass will be obtained from the given data. The biomass is continuously decreasing from secondary consumer (120 g) to primary consumer (60 g) to primary producer (10 g). Therefore, upright pyramid of biomass cannot be obtained. Secondary consumer (120g) Primary consumer (60g) Primary producer (10g) Inverted pyramid of biomass

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Q24. Choose the true/false statements from the given set.

1. Decomposition rate is higher when detritus is enriched with lignin and chitin.
2. The humus formed during humification is further degraded by some microbes and release inorganic nutrients via mineralisation process.

Choose the correct option.

1. I and II both are true
2. I is true, while II is false
3. I is false, while II is true
4. I and II both are false

Answer: (c)

Statement II is true, while I is false. The correct form of statement I is as follows Decomposition rate is higher when detritus is enriched within nitrogen and water soluble substances like sugar.

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Q25. Secondary succession occurs in:

1. Burned forest
2. Flooded land
3. Abandoned farm land
4. All of these

Answer: (d)

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Q26. Frog that feeds on insects, is a

1. secondary consumer
2. primary consumer
3. tertiary consumer
4. decomposer

Answer: (a)

Frog feeding on insects is secondary consumer.

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Q27. Pyramid of numbers is

1. Always inverted
2. Always upright
3. Either upright or inverted
4. Neither upright nor inverted

Answer: (c)

Pyramid of number in ecosystems can be either inverted or upright. In terrestrial ecosystem pyramids of number is upright. In case of successive decrease in members of trophic level like a big tree, it is inverted whereas pyramid of energy is always upright.

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Q28. ________ of the carbon is found dissolved in oceans, which is responsible for its regulation in atmosphere. Most appropriate word to fill the blank is

1. 81%
2. 51%
3. 61%
4. 71%

Answer: (d)

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Q29. Pyramid of number in a pond ecosystem is

1. inverted
2. irregular
3. upright
4. spindle-shaped

Answer: (c)

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Q30. Vertical distribution of different species occupying different levels in a biotic community is known as

1. stratification
2. divergence
3. zonation
4. pyramid

Answer: (a)

The vertical distribution of different species occupying different levels in a biotic community is known as stratification. It is the formation of vertical layers where vegetation is dense, i.e. there are about 5-7 strata (layer) in the tropical rainforests with trees, occupy top vertical strata, shrubs (the second layer below tree), herbs and grass occupy the bottom layers.

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Q31. Identify the food chain. Dead animal → Blow fly maggots → Common frog → Snake

1. Detritus food chain
2. Grazing food chain
3. Decomposer food chain
4. Predator food chain

Answer: (a)

The food chain in the question is detritus as, it starts from dead material (animal or plant).

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Q32. In parasitic food chain, the pyramid of number is

1. upright
2. linear
3. inverted
4. inverted upright

Answer: (c)

In parasitic food chain, the pyramid of number is always inverted, because a single plant may support the growth of many herbivore and each herbivore provides nutrition to several parasites, which supports many hyperparasites. Thus, the number of organisms gradually shows an increase.

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Q33. The rate of decomposition is dependent on ....... .

1. temperature and pH
2. chemical nature of detritus
3. moisture and aeration
4. All of the above

Answer: (d)

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Q34. If an ecosystem is composed of only three trophic levels then how much energy will be conserved at the III trophic level –

1. 20%
2. 30%
3. 10%
4. 1%

Answer: (d)

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Q35. The following graph depicts changes in two populations (A and B) of herbivores in a grassy field. A possible reason for these changes is that

1. Population A produced more offspring than population B
2. Population B competed more successfully for food than population A
3. Population A consumed the members of population B
4. Both plant populations in this habitat decreased

Answer: (b)

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Q36. The rate at which light energy is converted into chemical energy of organic molecules is the ecosystem's

1. net primary productivity
2. gross primary productivity
3. net secondary productivity
4. gross secondary productivity

Answer: (b)

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Q37. the rate at which light energy is converted into chemical energy of organic molecules is the ecosystem's

1. gross secondary productivity
2. net primary productivity
3. net secondary productivity
4. gross primary productivity

Answer: (d)

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Q38. Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?

1. Zooplankton
2. Fish
3. Frog
4. Phytoplankton

Answer: (b)

A single species may occupy more than one trophic level. In pond, fish occupy more than one trophic level. Small fishes act as secondary consumer. They feed on primary consumer. Large fishes act as tertiary consumer. They feed on smaller fish.

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Q39. Which of the following ecosystem has the highest gross primary productivity?

1. Coral reefs
2. Grasslands
3. Mangroves
4. Equatorial rain forest

Answer: (a)

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Q40. Vegetable eating person acts as

1. primary consumer
2. primary producer
3. secondary consumer
4. tertiary consumer

Answer: (a)

Vegetable eating person acts as primary consumers in an ecosystem. These are herbivores, which feed directly on producer (green plants).

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Q41. Most of the animals that live in deep oceanic waters are

1. Tertiary consumers
2. Secondary consumers
3. Detritivore
4. Primary consumers

Answer: (c)

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Q42. The primary succession refers to the development of communities on a

1. forest clearing after devastating fire.
2. freshly cleared crop field.
3. pond, freshly filled with water after a dry phase.
4. newly exposed habitat with no record of earlier vegetation.

Answer: (d)

Primary succession is the ecological succession occurring in an area where no organisms are found, like bare rocks, sand dunes etc.

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Q43. In what order do a hawk, grass and rabbit form a food chain in a meadow?

1. Grass → hawk → rabbit
2. Hawk → grass → rabbit
3. Rabbit → grass → hawk
4. Grass → rabbit → hawk

Answer: (d)

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Q44. The reservoir for the gaseous type of biogeochemical cycle exists in

1. atmosphere
2. stratosphere
3. ionosphere
4. lithosphere

Answer: (a)

In gaseous cycles, the main reservoirs of chemical are the atmosphere and ocean, e.g. carbon cycle, nitrogen cycle, oxygen cycle, etc.

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Q45. Intermediate community between pioneer and climax communities is called

1. Biotic community
2. Seral community
3. Temporary community
4. Ecosere

Answer: (b)

The various biotic communities that develop during biotic succession are termed as seral or transitional communities. The entire sequence of development stage of biotic succession from pioneer to a climax community is known as sere.

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Q46. Which of the following acts as "nature's scavengers"?

1. Man
2. Microorganisms
3. Insects
4. Animals

Answer: (b)

Microorganisms (bacteria and mould) are decomposers of the ecosystem. They feed upon dead decaying organisms (both plant and animals) and break them into simpler compounds. They are called nature's scavengers as they are consumers of dead matter.

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Q47. Bamboo plant is growing in a fir forest then what will be the trophic level of it?

1. Third trophic level ($T_3$)
2. Second trophic level ($T_2$)
3. First trophic level ($T_1$)
4. Fourth trophic level ($T_4$)

Answer: (c)

Trophic structure of ecosystem is a type of producer-consumer arrangement, in which each food level is called trophic level and the graphical representation of trophic structure of ecosystem constitutes ecological pyramids. The green plants are producers and represent the first trophic level ($T_1$). So bamboo plant is the first trophic level ($T_1$).

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Q48. Which ecosystem has the maximum biomass?

1. Lake ecosystem
2. Pond ecosystem
3. Grassland ecosystem
4. Forest ecosystem

Answer: (d)

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Q49. During ecological succession,

1. the establishment of a new biotic community is very fast in its primary phase
2. the gradual and predictable change in species composition occurs in a given area
3. the numbers and types of animals remain constant
4. the changes lead to a community that is in near equilibrium with the environment and is called pioneer community

Answer: (b)

The gradual and predictable change in the species compositon of a given area is called ecological succession. During succession, some species colonies an area and their populations become more numerous, whereas populations of other decline and even disappear.

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Q50. Which one of the following statements for the pyramid of energy is incorrect ?

1. It is inverted in shape.
2. It shows energy content of different trophic level organisms.
3. Its base is broad.
4. It is upright in shape

Answer: (a)

Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step.

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Q51. Consider the following statements about phosphorus cycle.

1. Major reservoirs or phosphorus are phosphate rocks and fossil bone deposits laid down in the past geological ages.
2. During weathering of rocks, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants.

1. Statement I is false, but II is true
2. Statement I is true, but II is false
3. Both statements I and II are true
4. Both statements I and II are false

Answer: (c)

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Q52. Grassland with scattered trees is called:

1. deciduous forest
2. savannah
3. evergreen forest
4. tropical rain forest

Answer: (b)

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Q53. Trophic levels are formed by

1. Only animals
2. Only plants
3. Only carnivores
4. Organisms linked in food chains

Answer: (d)

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Q54. How many trophic levels human beings function at in a food chain?

1. 2
2. 1
3. 3
4. 4

Answer: (c)

Human beings can function on three trophic levels. They are at

• Primary trophic level as primary consumer on plants.
• Secondary trophic level as secondary consumer.
• Tertiary trophic level as tertiary consumer.

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Q55. Which of these are true about humus?

1. Colloidal in nature
2. Dark coloured amorphous substance
3. Reservoir of nutrient
4. All of these

Answer: (d)

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Q56. Mass of living matter at a trophic level in an area at any time is called

1. detritus
2. standing crop
3. humus
4. standing state.

Answer: (b)

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Q57. Select the formula for ecological efficiency

1. ${\text"Food primary assimilated × 100"}/{\text"Food energy ingested"}$
2. ${\text"Gross primary productivity × 100"}/{\text"Incident total solar radiation"}$
3. ${\text"Net primary productivity × 100"}/{\text"Gross primary productivity"}$
4. ${\text"Energy in biomass production at a trophic level × 100"}/{\text"Energy in biomass production at previous trophic level"}$

Answer: (d)

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Q58. Ecosystem shows

1. Mineral cycling
2. Homeostasis
3. Energy flow
4. All of these

Answer: (d)

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Q59. Food chain refers to

1. animals gathered near a source of food
2. number of humans forming a chain for food
3. transfer of energy from producers to consumers
4. None of the above

Answer: (c)

The transfer of energy from producers to top consumers through a series of organisms is called food chain. It is always straight and proceed in a progressive straight line. In a food chain, the maximum population is of producers.

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Q60. Assertion: Of the incident solar radiation is less than 50 per cent of its PAR.

Reason: Plant captures 2 to 10 per cent of the PAR.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (a)

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Q61. Which of the following statements is/are not true?

1. Below ground detritus constitutes leaf litter, dried plant parts, remains of animals, their droppings and excretions.
2. Above ground detritus mainly constitutes dead roots, underground dead animals, etc.
3. Decomposition completely disposes off the whole detritus.
4. Humus is rich in chitin and lignin.

1. I, II and IV
2. I, II and III
3. I and II
4. II and III

Answer: (a)

Statements I, II and IV are not correct, whereas statement III is correct. The incorrect statements can be corrected as

• Above ground detritus constitutes leaf litter, dried plant parts, remains of animals, their droppings and excretions.
• Below ground detritus mainly constitutes dead roots and underground dead animals.
• Humus is rich in lignin and cellulose.

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Q62. Which one of the following has the largest population in a food chain?

1. Primary consumers
2. Producers
3. Secondary consumers
4. Decomposers

Answer: (b)

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Q63. Which is an example of true pyramid in an ecosystem?

1. Pyramid of number
2. Pyramid of biomass
3. Pyramid of energy
4. None of the above

Answer: (c)

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Q64. Which of the following is a characteristic feature of cropland ecosystem?

1. Least genetic diversity
2. Absence of soil organisms
3. Absence of weeds
4. Ecological succession

Answer: (a)

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Q65. Which of the following two organisms are producers?

1. Plants and consumers
2. Plants and phytoplanktons
3. Zooplanktons and phytoplanktons
4. Phytoplanktons and chlorophylls

Answer: (b)

Plants and phytoplanktons are producers. In a terrestrial ecosystem, plant grows by manufacturing food from carbon dioxide of air, water and minerals of soil with the help of chlorophyll and sunlight. Plants, thus act as the producer on land.

In a pond, phytoplankton (rooted and floating plants) synthesise food materials from dissolved nutrients by photosynthesis. They, thus act as the producers.

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Q66. Which of the following ecosystem has the highest gross primary productivity?

1. Grassland
2. Rainforest
3. Mangroves
4. Coral reef

Answer: (b)

Gross primary productivity is the total rate of photosynthesis, including the organic matter used up in respiration during the measurement period. Tropical evergreen/rainforests occur over equatorial/ subequatorial regions with abundant warmth and rainfall (200–350 cm/yr) almost throughout the year.

The forests are impenetrable (= jungle) with maximum diversity, e.g., 200 types of trees in one hectare, 70–80% of all insects 80–85% of all birds. Productivity is maximum here, 12000 kcal/$m^2$/yr.

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Q67. The organisms which used as food material but they are not killed by other organisms in a nature are called-

1. Secondary consumer
2. Primary consumer
3. Top consumer
4. Decomposers

Answer: (b)

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Q68. Which statement is true corresponding to the given food chain ? Grass → Rabbits → Snakes → Hawks

1. Each prey population has a greater biomass than its predator population.
2. Each predator population has a greater biomass than its prey population.
3. Each population is omnivorous.
4. Each level of food chain returns inorganic nutrients and energy to the producer.

Answer: (a)

In most ecosystems, all the pyramids of number, energy and biomass are upright i.e., producers are more in number and biomass than the herbivores and herbivores are more in number and biomass than the carnivores. Also energy at a lower trophic level is always more than that at a higher level.

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Q69. Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem, with four blanks (A to D). Identify the blanks.

Consumers .....C..... .....A..... Soil solution .....B..... Uptake Run off .....D.....

1. A: Litter fall, B: Producers, C: Rock minerals, D: Detritus
2. A: Rock minerals, B: Detritus, C: Litter fall, D: Producers
3. A: Detritus, B: Rock minerals, C: Producers, D: Litter fall
4. A: Producers, B: Litter fall, C: Rock minerals, D: Detritus

Answer: (c)

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Q70. Which ecosystem has the maximum biomass?

1. Pond ecosystem
2. Grassland ecosystem
3. Lake ecosystem
4. Forest ecosystem

Answer: (d)

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Q71. Assertion (A): Lichens are pioneer species on rocks.

Reason (R): They secrete acids to dissolve rocks, it helps in weathering and soil formation.

1. A and R are both incorrect
2. A and R are both correct
3. A is correct but R is incorrect
4. R is correct but A is incorrect

Answer: (b)

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Q72. The mass of living material at a trophic level at a particular time is called

1. standing crop
2. net primary productivity
3. gross primary productivity
4. standing state.

Answer: (a)

Standing crop is the total amount of living material in a specified population at a particular time, expressed as biomass (standing biomass) or its equivalent in terms of energy. The standing crop may vary at different times of the year for example, in a population of deciduous trees between summer and winter.

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Q73. Which one of the following is not a functional unit of an ecosystem?

1. Decomposition
2. Energy flow
3. Productivity
4. Stratification

Answer: (d)

Stratification represents the structural unit and is not the functional unit of ecosystem. Energy flow, productivity, decomposition and nutrient cycling are the functional unit of an ecosystem.

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Q74. Plant decomposers are

1. fungi and plants
2. monera and fungi
3. protista and animalia
4. animalia and monera.

Answer: (b)

Microorganisms (bacteria and fungi) are decomposers of the ecosystem. They feed upon dead decaying living organisms (both plant and animals) and break them into simpler compounds. These are released free in the atmosphere and are utilized by producers for the synthesis of their food materials. They mainly belong to monera and fungi.

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Q75. Which of the following process helps in nutrient conservation?

1. Leaching
2. Immobilisation
3. Mineralisation
4. Nitrification

Answer: (b)

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Q76. When man eats fish which feeds on zooplankton which have eaten small plants, the producer in the chain is

1. Small plants
2. Zooplankton
3. Fish
4. Man

Answer: (a)

Plants are producers which can prepare their food by the process of photosynthesis. Zooplanktons, fish and man are primary, secondary and tertiary carnivores respectively.

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Q77. DFC (Detritus Food Chain) begins with

1. Fungi
2. Dead organic matter
3. Bacteria
4. Plant

Answer: (b)

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Q78. Given below is one of the type of ecological pyramids. This type represents

1. pyramid of biomass
2. pyramid of energy in a grassland
3. pyramid of number in a lake
4. pyramid of energy in a fallow land

Answer: (a)

The figure represents pyramid of biomass which shows a sharp decrease in biomass at higher trophic level.

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Q79. Which of the following factor is contributing to an overload of the carbon cycle?

1. Cellular respiration
2. Photosynthesis
3. Deforestation
4. Afforestation

Answer: (c)

Anthropogenic activities mainly deforestation is contributing a lot in disturbing the balance of carbon cycling in nature.

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Q80. Tropical deciduous forest trees shed their leaves to:

1. save energy.
2. protect themselves from heat.
3. enhance rate of respiration.
4. prevent loss of water.

Answer: (d)

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Q81. Vegetation of a geographic region with low rainfall, high temperature, loose and sandy soil is of the type called:

1. scrub forest
2. grassland
3. xerophytic
4. evergreen tropical forest

Answer: (c)

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Q82. The largest ecosystem of the world is-

1. Great lakes
2. Grasslands
3. Forests
4. Oceans

Answer: (d)

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Q83. How many ecological pyramids are usually studied?

1. 2
2. 1
3. 3
4. 4

Answer: (c)

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Q84. A much larger fraction of energy flows in a terrestrial ecosystem through

1. detritus food chain
2. grazing food chain
3. complex food chain
4. food web aquatic ecosystem

Answer: (a)

In a terrestrial ecosystem, a much larger fraction of energy flows through the Detritus Food Chain (DFC) than through the Grazing Food Chain (GFC). DFC may be connected with the GFC at some levels. For example, some of the organisms of DFC are prey to the GFC animals.

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Q85. Assertion: Amount of nutrient present in the soil at any given time, in a given ecosystem is referred as the standing state.

Reason: Each trophic level has a certain mass of living material at particular time is known as the standing crop.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (a)

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Q86. Phosphorus is a major constituent of

1. Nucleic acids
2. Biological membrane
3. Cellular energy transfer system
4. All of these

Answer: (d)

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Q87. Read the following statements.

1. Identification and enumeration of plant and animal species of an ecosystem given its species composition.
2. Despite occupying about 70% of the surface, the productivity of the oceans are only 55 billion tons.
3. A constant input of solar energy is the basic requirement for any ecosystem to function and sustain.
4. Sugarcane have more efficiency to trap sunlight, so they accumulate more primary productivity.

Which of the statements given above are correct?

1. I and IV
2. I and II
3. I, II, III and IV
4. None of these

Answer: (c)

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Q88. Which of the following is expected to have the highest value (gm/$m^2$/yr) in a grassland ecosystem?

1. Gross production (GP)
2. Tertiary production
3. Secondary production
4. Net production (NP)

Answer: (a)

Productivity is rate of accumulation of energy containing organic matter by an ecosystem per unit area per unit time. It is of two types- primary and secondary. Productivity at producer level is known as primary productivity. It is two types: Gross primary productivity is primary productivity including that amount which is utilized in respiration and other metabolic activities. Net primary productivity (NPP) is primary productivity in excess to that which is utilised in respiration and other metabolic activities.

NPP = GP – Respiration

Secondary productivity is productivity at consumer level. Since gross production includes total production including the amount utilized in respiration and other metabolic activities so it is more than other forms of productivity.

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Q89. Complete the following model of carbon cycle filling A, B, C, D, E and F.

1. A–Photorespiration, B–Respiration, C–Respiration, D–Burning of organic debris, E–Pond food chain, F–Dolomite
2. A–Osmosis, B–Photosynthesis, C–Respiration, D–Burning of fuel wood, E–Forest food chain, F–Limestone
3. A–Respiration, B–Photosynthesis, C–Respiration, D–Combustion of fossil fuels, E–Aquatic food chain, F–Coal, oil
4. A–Respiration, B–Photosynthesis, C–Respiration, D–Burning of forest, E–Terrestrial food chain, F–Forest

Answer: (c)

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Q90. About 70% of total global carbon is found in

1. agroecosystems
2. grasslands
3. oceans
4. forests

Answer: (c)

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Q91. Which of following is/are trend(s) in from ecological succession ?

1. An increase in complexity of species.
2. An increase in productivity.
3. An increase in community stability and species diversity.
4. A decrease in non-living organic materials.

1. (i) and (iv)
2. (i) and (iii)
3. (i), (ii) and (iii)
4. (i), (ii), (iii) and (iv)

Answer: (c)

Ecological succession is the process by which the structure of a biological community changes and evolves over time. Two different types of succession (primary and secondary) have been distinguished.

Primary succession occurs in essentially lifeless areas-regions in which the soil is incapable of sustaining life as a result of factors such as lava flows, newly formed sand dunes, or rocks left from a retreating glacier.

Secondary succession occurs in areas where a community that previously existed has been removed; it is typified by smaller-scale disturbances that do not eliminate all life and nutrients from the environment.

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Q92. Which of the following is not a characteristic of humus?

1. It is highly resistant to microbial action and undergoes slow decomposition.
2. It is colloidal in nature and serves as a reservoir of nutrients.
3. It is rich in organic matter such as lignin and cellulose.
4. It is further degraded by the process of humification.

Answer: (d)

Humus constitutes the organic component of soil and is rich in lignin and cellulose. Humus is formed from organic remains through the activity of decomposer microorganisms. Process of formation of humus from raw organic remains is called humification. Humus is quite resistant to microbial action.

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Q93. Statement 1: Net primary productivity is gross primary productivity minus respiration.

Statement 2: Secondary productivity is produced by heterotrophs

1. Statement -1 is True, Statement -2 is True ; Statement-2 is NOT a correct explanation for Statement – 1
2. Statement- 1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement -1
3. Statement - 1 is True, Statement- 2 is False
4. Both the Statements are False.

Answer: (a)

Net primary productivity is the rate of organic matter built up or stored by producers in their bodies per unit time and area. Net productivity is equal to gross primary productivity minus loss due to respiration and other reasons.

Rate of increase in energy containing organic matter or biomass by heterotrophs or consumers per unit time and area is known as secondary productivity.

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Q94. In which of the following both pairs have correct combination?

Answer: (d)

Carbon and Nitrogen are gaseous nutrient cycle. Sulphur and phosphorus are sedimentary nutrient cycle.

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Q95. Ecosystems need a constant supply of energy

1. to counteract decreasing disorderliness
2. to counteract increasing disorderliness
3. to synthesise molecules
4. Both (b) and (c)

Answer: (d)

Ecosystems also follow second law of thermodynamics. They need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward increasing disorderliness.

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Q96. The dominant second trophic level, in a lake ecosystem, is

1. benthos
2. zooplankton
3. phytoplankton
4. plankton

Answer: (b)

Trophic level is a step or division of food chain which is characterized by the method of obtaining its food. The two fundamental trophic levels are producers and consumers. Producers belong to the first trophic level.

In a lake the producers are mainly some rooted or floating plants and phytoplanktons. Primary consumers form the second trophic level. They feed on living plants or plant parts. The primary consumers are zooplanktons.

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Q97. Identify A, B and C from the given flowchart.

1. A– Beetle, B– Lizard, C– Praying mantis
2. A– Bulbul, B– Snake, C– Monkey
3. A– Ladybird, B– Snake, C– Hawk
4. A– Lizard, B– Bird, C– Snake

Answer: (c)

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Q98. Which ecosystem does not show variations dependent upon geographic location and rainfall?

1. Fresh water ecosystem
2. Marine ecosystem
3. Desert ecosystem
4. Tropical ecosystem

Answer: (b)

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Q99. In which of the following interactions both partners are adversely affected ?

1. Competition
2. Mutualism
3. Predation
4. Parasitism

Answer: (a)

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Q100. Which of the following is the most stable ecosystem?

1. Ocean
2. Mountain
3. Forest
4. Desert

Answer: (a)

Of all the ecosystems, ocean is the largest and most stable ecosystem. Aquatic life is protected from vigorous climates and weather that are climatic conditions, problem of water supply, food, fire and artificial forces such as industrialization, farming and grazing are lacking in the oceans. The sea is continuous and not separated as land and freshwater habitats.

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