NCERT Exemplar Class 12 Biology Chapter 14 Solutions: Ecosystem

NCERT Exemplar Class 12 Biology Solutions Chapter 14 is based on the topic of ecosystems. Ecosystem can be described as a functional unit of nature where living organisms interact within themselves as well as their physical environment. Ecosystems have a wide range, from a small pond to a vast sea. In this chapter of NCERT Exemplar Class 12 Biology, ecosystems are broadly categorized into terrestrial and aquatic systems. Forest, desert, grassland are some of the examples of a terrestrial ecosystem. Aquatic ecosystem comprises sea, river, pond, lake, etc. 

This chapter gives insight into the structure of an ecosystem and looks into the input or productivity, transfer of energy like food chain and nutrient cycle, output like degradation and energy loss, the energy flow inside the system because of inter-relationship between different entities of the system. This chapter also highlights various cycles, webs, and chains around these energy flows. There are a total of 13 questions to solve exemplar problems of NCERT Class 14 Biology. There is only 1 set of exercise which has a combination of questions such as fill in the blanks, objective types, and questions involving long answers and short answers.

NCERT Exemplar Problems Class 12 Biology has advanced concepts which could be difficult for students to grasp with just a textbook explanation. Instasolv brings a change in approach by having its team of experts prepare easy solutions to every question. These methods of answering enable you to do efficient time management as well.

Important Topics for NCERT Biology Exemplar Solutions Class 12 Chapter 14

  • Structure and function of the ecosystem – The components of an ecosystem are divided into abiotic and biotic. Interaction between these 2 components forms the physical structure of a given ecosystem. Stratification is the vertical distribution of different species of an ecosystem in layers. For e.g.: in a forest, trees are the top layer, shrubs the 2nd and grasses occupy the 3rd level. The functional components of an ecosystem are:
      1. Productivity
      2. Decomposition
      3. Energy flow
      4. Nutrient cycle
  • Productivity – Solar energy is needed for any ecosystem to sustain and function. Productivity is of 2 types:
    • Primary productivity – During photosynthesis, plants produce biomass or organic matter which when measured per unit area over a period of time gives the productivity of that ecosystem. The unit of productivity is the weight (g-2) or energy (kcal m-2). This is further divided into:
      1. Gross primary productivity (GPP) – rate at which organic matter is produced in an ecosystem.
      2. Net primary productivity – When you reduce respiration losses from GPP you get NPP


    • Secondary productivity – The rate at which new organic matter is produced by consumers defines secondary productivity.

Annual net productivity of entire biosphere 170 billion tons of organic matter

  • Decomposition – The process of breaking down organic matter into water, CO2, and nutrients is called decomposition. Some key definitions here are:
    • The remains of dead plants and dead animals are called detritus.
    • Fragmentation occurs when Detritivores like earthworm breakdown detritus into smaller particles like woodlice, dung flies, etc.
    • Water-soluble organic nutrients go into the soil horizon and become unavailable salts, this is called Leaching.
    • Detritus is degraded into simple inorganic substances by the bacterial and fungal enzyme which is known as catabolism.
    • When dark-coloured amorphous substances gather, that is the process of humification.
    • Mineralization occurs when there is a release of nutrients when humus is further degraded by some microbes.

Decomposition is favoured by a warm and moist environment and all the processes which are part of decomposition happen simultaneously on the detritus.

  • Energy Flow – The only source of energy for the entire ecosystem of earth, barring deep sea hydro-thermal ecosystems, is the Sun. Solar radiation has only 50% of PAR (photosynthetically active radiation), of which plants capture only 2-10% and that is responsible for sustaining the entire living world. The energy thus flows from plants to all living organisms.
    • Producers – Organisms depend on their food for producers. So the flow of energy is unidirectional. Green plants of the ecosystem are producers.
    • Consumers – All animals get their food from producers and are called consumers. Consumers who feed on producers are primary consumers also called herbivores like grass.
    • Consumers who feed on herbivores are called secondary consumers or primary carnivores like goats.
    • Consumers who feed on primary carnivores are called tertiary consumers or secondary carnivores.
    • Food chain –Place of a specific organism in the food chain is based upon their source of nutrition or food and that place is termed as a trophic level.
      1. Producers – 1st trophic level
      2. Herbivores – 2nd trophic level
      3. Carnivores – 3rd trophic level

Flow of energy from one trophic layer to another, by either eating or by being eaten up, constitutes the Food Chain. It has 2 types:

        • Grazing food chain – Starting from producers, ends on carnivores, through herbivores. E.g. grass -> goat -> man
        • Detritus food chain – Starting from detritus, ends on organisms who feed on detritivores. E.g. grass -> insects -> frogs
  • Ecological pyramidA graphical representation of various trophic levels of the food chain constitute an ecological pyramid. It depicts their biomass, number, and energy. 
  • Ecological succession – The species composition of a given area changes in a predictable way and is termed as ecological succession. This change finally reaches equilibrium with the environment and that community is called the climax community.
  • Nutrient Cycle – Movement of nutrients between biotic and abiotic elements of an ecosystem is known as a nutrient or biogeochemical cycle. 
  • Nutrients are needed by organisms constantly to grow, reproduce, and regulate their body functions
  • Standing state is the amount of nutrients in the soil at any point in time.
    • There are 2 types of nutrient cycle:
      1. Gaseous – cycle of nitrogen, carbon, etc.
      2. Sedimentary – cycle of phosphorus, sulphur, etc

Discussion of Exercises of NCERT Exemplar Class 12 Biology Solutions Chapter 14

  1. There is only one set of questions which are a mix of fill in the blanks, short, and long answers. These well-presented questions touch all the topics like components of an ecosystem, food chain, trophic levels, producers and consumers, PAR, ecological pyramid, energy flow, sedimentary and carbon cycle. There are many questions which require a descriptive answer and brush all subtopics of a given topic. There are a total of 13 questions.
  2. The NCERT Exemplar Problems for all chapters of CBSE Class 12 Biology are one of the most reliable sources for preparing for CBSE or other competitive exams. By answering these questions students get to clear many concepts and doubts around the subject.

Why Use NCERT Biology Exemplar Solutions Class 12 Chapter 14 by Instasolv?

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