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Q1. The ‘10 Percent Law’ is related to

• Mendelian genetics
• Non-Mendelian genetics
• Energy transfer from a lower trophic level to a higher trophic level
• Energy consumption during photosynthesis in C₄ plants

Solution

The ‘10 Percent Law’ implies that exactly 90% of the energy is lost in the transfer at each trophic level, and that only 10% is passed on as biological energy. According to this law, during the transfer of energy from organic food from one trophic level to the next, only 10% of energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration or lost to incomplete digestion by higher trophic levels.

Q2. The loss of energy as one proceeds from one trophic level to the next trophic level is approximately

• 30%
• 40%
• 60%
• 90%

Solution

Nearly 90% of energy is lost when it moves from one trophic level to the next because there is a decrease in the content and flow of energy with the rise in trophic level.

Q3. Select the correct match: A. Sedimentary nutrient cycle - Nitrogen cycle B. Pioneer species - Lichens C. Secondary succession - Burnt forests D. Pyramid of biomass in sea - Upright

• A, B and D only
• A and C only
• B and C only
• B and D only

Solution

In primary succession on rocks, the pioneer community is the lichen stage which brings about slow weathering of rocks and formation of soil leading to secretion of lichen acids. The lichen acids slowly corrode the rock surface and release minerals required for the proper growth of lichens. Secondary succession occurs in a forest area due to deforestation which may be due to a forest fire or severe drought.

Q4. Which one of the following statements for pyramid of energy is incorrect, whereas the remaining three are correct?

• Its base is broad.
• It shows energy content of different trophic levels.
• It is inverted in shape.
• It is upright in shape.

Solution

The pyramid of energy can never be inverted. It is always upright because at each transfer about 80-90% of the energy available at the lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to the next trophic level.

Q5. The first stable product of fixation of atmospheric nitrogen in leguminous plants is

• N0₂⁻
• Ammonia
• N0₃⁻
• Glutamate

Solution

Biological nitrogen fixation occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase.

Q6. The amount of carbon fixed in a year through photosynthesis produces about

• 7 × 10¹¹ kg
• 7 × 10¹³ kg
• 14 × 10¹¹ kg
• 14 × 10¹³ kg

Solution

The amount of carbon fixed in a year through photosynthesis is about 7 × 10¹³ kg.

Q7. In a food chain, the total amount of living material is depicted by

• Pyramid of biomass
• Trophic levels
• Pyramid of numbers
• Pyramid of energy

Solution

The amount of living organic matter is called biomass. The pyramid of biomass is a graphic representation of biomass present sequence-wise per unit area of different trophic levels with producers at the base and top carnivores at the top.

Q8. Which one of the following is considered as a pioneer community in xerarch?

• Annual herb
• Perennial herb
• Forest stage
• Lichen

Solution

The sequence of successional stages which occur on dry land is called xerarch. In dry land, the pioneer community is the lichen stage which brings about slow weathering of rocks and formation of soil leading to secretion of lichen acids. The lichen acids slowly corrode the rock surface and release minerals which are required for the proper growth of lichens.

Q9. The important steps in the process of decomposition are

• Fragmentation and mineralisation
• Leaching and catabolism
• Humification and mineralisation
• All of the above

Solution

Decomposition is the physical and chemical breakdown of complex organic remains by the decomposers. Various processes include fragmentation, mineralisation, leaching, catabolism and humification. The smaller fragments from a particular body are immobilised as a part of the detritus comes out undigested and are called fragmentation. Mineralisation is the release of inorganic substances, both non-mineral and mineral, from organic matter. Soluble substances formed during decomposition are subjected to leaching or passage to deep layers of soil/ground water by percolating water. The decomposers change insoluble complex organic substances into simple and soluble organic compounds and inorganic substances which is called catabolism. Humification is the process of formation of humus from detritus or organic remains.

Q10. Changes in the body form of some planktonic animals with seasonal changes in temperature are called:

• Anamorphosis
• Cyclomorphosis
• Metamorphosis
• Heteromorphosis

Solution

Cyclic recurrent polymorphism in certain planktonic fauna in response to seasonal temperature or salinity changes is said to be cyclomorphosis.

Q11. Approximately what amount of energy is available to one trophic level from one trophic level lower to it?

• 1%
• 10%
• 20%
• 30%

Solution

In the transfer of food energy from one trophic level to the other, only about 10% is stored at a higher trophic level and the remaining 90% is lost in respiration, decomposition and waste.

Q12. Which of the following is a transducer?

• Tiger
• Rabbit
• Grasshopper
• Grass

Solution

A transducer is an organism which has the ability to convert energy from one form to the other. Because producers can convert solar energy to chemical energy, they are also referred to as transducers. Because grass is a producer, it is also a transducer.

Q13. Secondary productivity is the rate of formation of new organic matter by

• Producer
• Parasite
• Consumer
• Decomposer

Solution

The rate of resynthesis of organic matter by consumers is known as secondary productivity. It depends on the loss while transferring energy-containing organic matter from the previous trophic level in addition with consumption due to respiration and predation.

Q14. The statement ‘Tiger is the apex of the food chain’ indicates:

• Tiger is a carnivore.
• Tiger has many enemies.
• Tiger has maximum biomass.
• Tiger is dependent upon a large number of herbivores and even large number of trees.

Solution

Nothing eats the tiger and that is why it is known as ‘the apex of the food chain’, indicating that the tiger is a carnivore.

Q15. Biosphere means

• Atmosphere
• Lithosphere and ionosphere
• Atmosphere, lithosphere and hydrosphere
• Hydrosphere, lithosphere and ionosphere

Solution

Biosphere is the sum of all ecosystems and comprises atmosphere, lithosphere and hydrosphere.

Q16. In a pyramid of numbers, in a grassland ecosystem, the largest population is that of

• Producers
• Tertiary consumers
• Secondary consumers
• Primary consumers

Solution

The maximum number of individuals occurs at the producer level in a grassland ecosystem.

Q17. Which one of the following is a denitrifying bacterium?

• Nitrobacter
• Nitrosomonas
• Pseudomonas
• Escherichia coli

Solution

Nitrites and nitrates are converted by the denitrifying bacteria Pseudomonas into nitrogen, which escapes into the atmosphere and is lost from the cycle.

Q18. Primary succession occurs in

• Previously unoccupied area
• Previously occupied area
• Both of the above
• None of the above

Solution

The natural development of a biotic community which occurs on a previously sterile or bare area is called primary succession. Some examples of primary succession include dunes and igneous rocks.

Q19. Ecosystem creates

• Food chains
• Food web
• Both of these
• Only food chain

Solution

In an ecosystem, all the living organisms are linked in a systematic chain for feeding habits called a food chain and also for interlocking food chains called a food web.

Q20. Which types of the following pyramids are never inverted?

• Pyramid of energy
• Pyramid of biomass
• Pyramid of numbers
• Pyramid of dry biomass

Solution

The pyramid of energy is never inverted because the maximum amount of the energy available at the lower trophic level is used up to overcome its entropy and to perform metabolic activities.

Q21. Which one of the following statements is correct for secondary succession?

• It begins on a bare rock.
• It occurs on a deforested site.
• It follows primary succession.
• It is similar to primary succession except that it has a relatively fast pace.

Solution

Secondary succession occurs in a forest area due to deforestation which may be due to a forest fire or severe drought.

Q22. An inverted pyramid of numbers and an inverted pyramid of biomass are respectively seen in

• Grassland and tree ecosystems
• Sea and tree ecosystems
• Tree and sea ecosystems
• Sea and grassland ecosystems

Solution

In a tree ecosystem, the pyramid of numbers is inverted because the number or biomass at the producer level is minimum and increases at each trophic level and is similar in the case of sea ecosystem.

Q23. Decomposers are

• Animalia and Monera
• Protista and Monera
• Fungi and Plantae
• Bacteria and Fungi

Solution

Decomposition is the chemical breakdown of complex organic remains by decomposers brought about by bacteria and fungi.

Q24. A biome is

• Sum of ecosystems in a geographical area
• Sum of all ecosystems on the Earth
• Biotic components in a population
• Biotic components in an ecosystem

Solution

The biome is a complex biotic community characterised by plant and animal species and maintained under climatic conditions of the region. It is the total of all ecosystems.

Q25. In an aquatic ecosystem, the trophic level equivalent to cows in a grassland is

• Phytoplankton
• Zooplankton
• Nekton
• Benthos

Solution

The cows in a terrestrial ecosystem are herbivores or primary consumers. Similarly, in an aquatic system, the zooplankton are the herbivores.

Q26. Detritivores break down the detritus by the process called

• Leaching
• Fragmentation
• Humification
• Mineralisation

Solution

When the detritivores feed on large fragments, small fragments are left undigested. The part digested by detritivores is immobilised. Due to fragmentation, left-over detritus comes out.

Q27. Which one of the following is not a gaseous biogeochemical cycle in an ecosystem?

• Oxygen cycle
• Phosphorus cycle
• Nitrogen cycle
• Carbon cycle

Solution

In gaseous cycles, the reservoir for elements like oxygen, carbon and nitrogen is in the atmosphere. Phosphorus is an element which is present in the sediments of the Earth. Therefore, the phosphorus cycle is called a sedimentary cycle.

Q28. This is an inverted pyramid:

• Pyramid of numbers in a grassland
• Pyramid of energy in a pond ecosystem
• Pyramid of biomass in a grassland
• Pyramid of biomass in a pond ecosystem

Solution

An inverted pyramid is formed when the number of individuals or biomass is minimum and increases at each trophic level. The pyramid of biomass in a pond ecosystem is an example of an inverted pyramid because the biomass of phytoplankton may be smaller than that of zooplankton.

Q29. During the food chain, the maximum energy is stored in

• Producers
• Decomposers
• Herbivores
• Carnivores

Solution

The maximum amount of energy is used by the producers as solar energy which uses 1000 Kcal because 90% of energy is lost when it moves from one trophic level to the next.

Q30. Most food chains are composed of how many trophic levels?

• 1 or 2
• 3 or 4
• 9 or 10
• More than 16

Solution

The maximum number of trophic levels is hardly 3 to 5 in terrestrial ecosystems and 4 to 6 in aquatic ecosystems. The lesser number of trophic levels is due to consumption of lot of energy through respiration.

Q31. Germplasm conservation at liquid N₂ temperature is

• Stratification
• Cryopreservation
• Scarification
• None of the above

Solution

The preservation of germplasm in liquid nitrogen at −198°C is called cryopreservation. Stratification is the formation of vertical layers where vegetation is dense. Scarification is a different term for skin etching or scratching.

Q32. Which of the following is a characteristic of a food web?

• Interlinking food chains
• Checking overpopulation
• Ecosystem development
• All of the above

Solution

Characteristics of a food web: They are made of interlinking food chains. They provide alternative pathways for food availability. They help check overpopulation as organisms depend on each other for food. They help in ecosystem development. 

Q33. Which one of the following is not used for construction of ecological pyramids?

• Dry weight
• Number of individuals
• Rate of energy flow
• Fresh weight

Solution

Ecological pyramids are usually prepared considering three ecological parameters - number of individuals, rate of energy flow and dry weight.

Q34. Which of the following forms the starting point of a detritus food chain?

• Fallen leaves of trees
• Detritivores
• Insects
• Lizard

Solution

In a detritus food chain, fallen leaves form the start of the food chain. The fallen leaves are eaten by detritivores, which in turn are eaten by smaller insects, which become food for the lizard.

Q35. In primary succession on rocks, the pioneer species are usually

• Algae
• Fungi
• Lichens
• Bryophytes

Solution

In primary succession on rocks, the pioneer community is the lichen stage which brings about slow weathering of rocks and formation of soil leading to secretion of lichen acids. The lichen acids slowly corrode the rock surface and release minerals required for the proper growth of lichens.

Q36. Azotobacter and Beijerinckia are examples of

• Symbiotic nitrogen fixers
• Non-symbiotic nitrogen fixers
• Ammonifying bacteria
• Disease causing bacteria

Solution

Azotobacter and Beijerinckia are free-living species (non-symbiotic) of bacteria which can fix nitrogen in the rhizosphere of several plants.  

Q37. Maximum CO₂ fixation is done by

• Green plants
• Phytoplanktons
• Zooplanktons
• Bacteria

Solution

First, carbon dioxide is fixed by the producers, which include the phytoplankton in an aquatic food chain. It then passes to zooplankton (herbivores) and so on.

Q38. The Y-shaped energy flow model was pioneered by

• H. T. Odum
• Teal
• Weismann
• Lindemann

Solution

The Y-shaped energy flow model was pioneered by H. T. Odum.

Q39. Which of the following pyramid of numbers is not upright?

• Pond ecosystem
• Desert ecosystem
• Tree ecosystem
• Forest ecosystem

Solution

The pyramid of numbers is always upside down because a tree will support a huge number of insects, or a flea-infested dog will support a large number of fleas. The biomass of the insects is smaller than the biomass of their food, but the numbers of insects are greater.

Q40. The composition of the atmosphere is somewhat stable up to a height of ____ above the Earth’s surface.

• 50 km
• 20 km
• 10 km
• 80 km