April 1, 2024

Here are simplified, step-by-step explanations for NCERT Solutions for Class 12 Science Biology Chapter 14 on Ecosystem. These solutions are highly favored by Class 12 Science students studying Biology, as they assist in swiftly completing homework assignments and preparing for exams. All questions and answers from the NCERT Book of Class 12 Science Biology Chapter 14 are presented here at no cost, making them easily accessible to you. Page No 256: Question 1: Fill in the blanks. (a) Plants are called as_________ because they fix carbon dioxide. (b) In an ecosystem dominated by trees, the pyramid (of numbers) is _________ type. (c) In aquatic ecosystems, the limiting factor for the productivity is _________. (d) Common detritivores in our ecosystem are_________. (e) The major reservoir of carbon on earth is_________. ANSWER: (a) Plants are called as   autotrophs   becausethey fix carbon dioxide. (b) In an ecosystem dominated by trees, the pyramid(of numbers) is of inverted type. (c) In aquatic ecosystems, the limiting factor forproductivity is light . (d) Common detritivores in our ecosystem are earthworms. (e) A major reservoir of carbon on Earth is Oceans. Page No 257: Question 2: Which one of the following has the largest population in a food chain? (a) Producers (b) Primary consumers (c) Secondary consumers (d) Decomposers ANSWER: (d) Decomposers Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals. Page No 257: Question 3: The second trophic level in a lake is- (a) Phytoplankton (b) Zooplankton (c) Benthos (d) Fishes ANSWER: (b) Zooplankton Zooplankton are primary consumers in aquatic food chains that feed upon phytoplankton. Therefore, they are present at the second trophic level in a lake. Page No 257: Question 4: Secondary producers are (a) Herbivores (b) Producers (c) Carnivores (d) None of the above ANSWER: (d) None of the above Plants are the only producers. Thus, they are called primary producers. There are no other producers in a food chain. Page No 257: Question 5: What is the percentage of photosynthetically active radiation (PAR), in the incident solar radiation. (a) 100% (b) 50 % (c) 1-5% (d) 2-10% ANSWER: (b) 50% Out of total incident solar radiation, about fifty percent of it forms photosynthetically active radiation or PAR. Page No 257: Question 6: Distinguish between (a) Grazing food chain and detritus food chain (b) Production and decomposition (c) Upright and inverted pyramid (d) Food chain and Food web (e) Litter and detritus (f) Primary and secondary productivity ANSWER: (a) Grazing food chain and detritus food chain   Grazing food chain   Detritus food chain 1. In this food chain, energy is derived from the Sun. 1. In this food chain, energy comes from organic matter (or detritus) generated in trophic levels of the grazing food chain. 2. It begins with producers, present at the first trophic level. The plant biomass is then eaten by herbivores, which in turn are consumed by a variety of carnivores. 2. It begins with detritus such as dead bodies of animals or fallen leaves, which are then eaten by decomposers or detritivores. These detritivores are in turn consumed by their predators. 3. This food chain is usually large. 3. It is usually smaller as compared to the grazing food chain. (b) Production and decomposition   Production   Decomposition 1. It is the process of producing organic matter (food) by producers. 2. It is the process of breaking down of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw material such as CO2, H2O, and other nutrients. 2. It depends on the photosynthetic capacity of the producers. 2. It occurs with the help of decomposers. 3 Sunlight is required by plants for primary production. 3. Sunlight is not required for decomposition by decomposers (c) Upright and inverted pyramid   Upright pyramid   Inverted pyramid 1. The pyramid of energy is always upright. 1. The pyramid of biomass and the pyramid of numbers can be inverted. 2. In the upright pyramid, the number and biomass of organisms in the producer level of an ecosystem is the highest, which keeps on decreasing at each trophic level in a food chain. 2. In an inverted pyramid, the number and biomass of organisms in the producer level of an ecosystem is the lowest, which keeps on increasing at each tropic level. (d) Food chain and Food web   Food chain   Food web 1. It is a single linear sequence of organisms. 1. It contains a number of interconnected food chains. 2. Members present at higher trophic levels feed on single types of organisms. 2. One organism has alternate food sources. (e) Litter and detritus   Litter   Detritus 1. Litter contains all kinds of wastes generated above the ground. 1. Detritus is composed of the remains of dead plants and animals. 2. Litter contains both biodegradable and non-biodegradable matter. 2. Detritus contains only biodegradable matter. (f) Primary and secondary productivity   Primary productivity   Secondary productivity 1. It is defined as the amount of organic matter produced by producers per unit area over a period of time. 1. It is defined as the rate of production of organic matter by consumers over a period of time. Page No 257: Question 7: Describe the components of an ecosystem. ANSWER: An ecosystem is defined as an interacting unit that includes both the biological community as well as the non-living components of an area. The living and the non-living components of an ecosystem interact amongst themselves and function as a unit, which gets evident during the processes of nutrient cycling, energy flow, decomposition, and productivity. There are many ecosystems such as ponds, forests, grasslands, etc. The two components of an ecosystem are: (a) Biotic component: It is the living component of an ecosystem that includes biotic factors such as producers, consumers, decomposers, etc. Producers include plants and algae. They contain chlorophyll pigment, which helps them carry out the process of photosynthesis in the presence of light. Thus, they are also called converters or transducers. Consumers or heterotrophs are organisms that are directly (primary consumers) or indirectly (secondary and tertiary consumers) dependent on producers …

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