Ecology

Total Questions: 88

41. Which one of the following is the correct sequence of a food chain? [I.A.S. (Pre) 2014]

(a) Diatoms-Crustaceans-Herrings
(b) Crustaceans-Diatoms-Herrings
(c) Diatoms-Herrings-Crustaceans
(d) Crustaceans-Herrings-Diatoms

Correct Answer: (a) Diatoms-Crustaceans-Herrings

Solution:The correct order of a common marine food chain is Diatom- Crustaceans- Herrings

Diatoms: These are microscopic, unicellular algae that are primary producers in aquatic ecosystems, meaning they convert sunlight into energy through photosynthesis.

Crustaceans: These are a diverse group of arthropods (like crabs, shrimp, and krill) that are herbivores, feeding directly on diatoms.

Herrings: These are fish that primarily eat crustaceans, making them secondary consumers in this food chain.

42. The primary source of energy in Eco-body is - [U.P.P.C.S. (Mains) 2015 ]

(a) Energy emitted by fermentation
(b) Preserved vegetable sugar
(c) Solar energy
(d) None of the above.

Correct Answer: (c) Solar energy

Solution:Solar energy is the primary source of energy in the ecological body. It is the driving force of an ecosystem. It fuels the entire food chain, starting with plants that use sunlight for photosynthesis. This converted chemical energy then becomes available to other organisms through the food web. Plants, the base of most ecosystems, utilize solar energy to convert carbon dioxide and water into sugars, a process called photosynthesis. The Sun's energy powers all life on Earth, including regulating weather patterns and maintaining the Earth's temperature.

43. Driving force of an ecosystem in [U.P.B.E.O. (Pre) 2019, U.P.R.O./A.R.O. (Re-Exam) Pre 2016 ]

(a) Carbohydrate
(b) Biomass
(c) Carbon
(d) Solar energy

Correct Answer: (d) Solar energy

44. Which of the following statements is correct? [U.P.P.C.S. (Pre) (Re. Exam) 2015 ]

(a) The energy flow in the biospheric ecosystem is unidirectional.
(b) The energy flows in the biospheric is cyclical.
(c) Relative loss of energy in natural ecosystem decrease with increasing trophic levels.
(d) Species at progressively higher trophic levels appear to be less efficient in using available energy

Correct Answer: (a) The energy flow in the biospheric ecosystem is unidirectional.

Solution:The flow of energy in the ecosystem is unidirectional (or one-directional). The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on from one organism to another in a food chain. The energy given out by the organisms as heat is lost to the environment. It does not return to be used by the plants again. This makes the flow of energy in the ecosystem 'unidirectional'. According to the first law of thermodynamics, energy can neither be created nor be destroyed in an isolated system. According to the second law whenever energy transforms into a new form, there is evident decay in its intensity. Similarly, with increasing trophic levels availability of energy decreases in the natural ecosystem.

45. 10 percent law is related with : [Chhattisgarh P.C.S. (Pre) 2016 ]

(a) Transfer of energy as food from one trophic level to other
(b) Transfer of heat from one matter to another
(c) Transfer of birds from one zone to another
(d) Transfer of water from one zone to another
(e) None of these

Correct Answer: (a) Transfer of energy as food from one trophic level to other

Solution:The Ten Percent Law of transfer of energy from one trophic level to the next was introduced by Raymond Lindeman in first half of 1940s. According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of the 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 level. When organisms are consumed, 10% of the energy in the food is fixed into flesh and is available for next trophic level (carnivores or omnivores). When a carnivore or an omnivore consume that animal, only about 10% of energy is fixed in its flesh for the higher level. Thus, at every level of the food chain (first, second, third and top level), the consumer converts only 10% of the accumulated energy int0 his body weight.

46. The pyramid of energy in any ecosystem is [M.P.P.C.S. (Pre) 2020]

(a) Always upright
(b) May be upright and inverted
(c) Always inverted
(d) None of the above

Correct Answer: (a) Always upright

Solution: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. Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time or annually per unit area. Hence option (a) is correct.

47. Trophic levels are formed by - [U.P.P.C.S. (Pre) 2023]

(a) Carnivorous animals
(b) Plants only
(c) Animals only
(d) Organisms linked in food chain

Correct Answer: (d) Organisms linked in food chain

Solution:Trophic levels are formed by interconnected organisms in a food chain, representing the flow of energy and nutrients producers, like plants, convert sunlight (solar energy) into chemical energy, while primary consumers eat producers. Secondary consumers feed on primary consumers and this sequence continues with tertiary consumers and beyond. Each level in the food chain represents a trophic level, showing the transfer of energy and nutrients between organism. Thus, option (d) is the correct choice as it includes all organisms linked in a food chain.

48. The amount of energy during the transfer from one trophic level to another in an ecosystem- [U.P. R.O./A.R.O. (Pre), 2017, U.P.P.C.S. (Pre) 2019]

(a) Increases
(b) Decreases
(c) Remains constant
(d) May increases or decrease

Correct Answer: (b) Decreases

Solution:Energy is the basic force responsible for all metabolic activities. The flow of energy from producer to top consumers is called energy flow, which is unidirectional. Energy flows through the trophic levels i.e. from producers to subsequent trophic levels. This energy always flows from lower (producer) to higher (herbivore, carnivore, etc.) trophic level. There is a loss of some energy in the form of unusable heat at each trophic level so the amount of energy during the transfer from one trophic level to another decreases in an ecosystem.

49. The highest trophic level in an ecosystem is obtained by : [U.P.U.D.A./L.D.A.(Pre) 2002]

(a) Herbivores
(b) Carnivores
(c) Omnivores
(d) Decomposers

Correct Answer: (c) Omnivores

Solution:There are four types of trophic levels in the food chain of the ecosystem. They are-

First trophic level- Producer

Second trophic level- Primary consumers (herbivorous)

Third trophic level- Secondary consumers (carnivorous)

Fourth trophic level- Tertiary consumers (omnivorous)

Decomposers feed on all the above trophic levels. Hence option (c) is the correct answer.

50. Biomass Pyramid is reversed in which type of ecosystem? [U.P.P.S.C. (GIC) 2010]

(a) Forest
(b) Pond
(c) Grassland
(d) Drylands

Correct Answer: (b) Pond

Solution:The Pyramid of Biomass is a graphical representation that depicts the extent of biomass per unit area within different trophic levels in an ecological system. In grasslands and forests, there is a gradual decrease in the biomass of organisms at successive levels from the producers to the top carnivores. Thus, pyramids are upright. However, in a pond, as the producers are small organisms, their biomass is least and this value gradually shows an increase towards the apex of the pyramid, thus making the pyramid inverted in shape.

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