Xam Idea Class 12 Biology Chapter 14 Solutions: Ecosystem

Xam Idea Class 12 Biology Solutions Chapter 14 ‘Ecosystem’ are based on the latest CBSE Class 12 syllabus. Our solutions will explain to you everything about the functional unit of nature called an ecosystem. They will help you learn about the important concepts of the chapter such as the structure of the ecosystem and the relationships between different components of an ecosystem. You can now easily clear all your doubts related to the chapter and prepare well for your CBSE Class 12 board exams.

Xam Idea Class 12 Biology Solutions Ecosystem solutions consist of 115 questions. The exercise is divided into four sections that are very short answer type questions, short answer type questions-I, short answer type questions-II and Long answer type questions. All questions are designed in accordance to the class 12 CBSE syllabus and also include questions from previous year’s exams. Our solutions will help you answer all kinds of questions related to energy flow, productivity, ecological pyramids, decomposition, nutrient cycling, ecological succession and ecosystem services.

The solutions provided by Instasolv for the questions presented in Xam Idea Class 12 Biology Chapter 14 are elaborative, with all detailed answers as well as required diagrams. Our team of experts are highly skilled and provide you with all accurate and updated solutions to the exercise questions of this chapter Ecosystem. The solutions will offer you deep insights into the ecosystem structure, energy transfer through the food chain, nutrient cycle and about the outputs through degradation and loss of energy.

 Important Topics for Xam Idea Class 12 Biology Solutions Chapter 14: Ecosystem

An ecosystem is the functional unit of nature where every living organism interacts with each other along with the surrounding physical environment.

The two basic ecosystems are

  • A terrestrial ecosystem that includes the forest, desert and the grassland ecosystem
  • An aquatic ecosystem that includes the pond, wetland, estuary, and Lake Ecosystem.

Structure and Function of the Ecosystem

  • The interaction that occurs in between several biotic and abiotic parts of the ecosystem helps in the ecosystem maintenance.
  • Stratification: It is the vertical distribution of various species at various levels. Like the tree occupies the top strata of a forest, then the shrubs and the bottom layers are occupied by the herbs and the grasses.
  • The important components of the ecosystem are productivity, decomposition, energy flow and nutrient cycling. In a pond ecosystem, some of the important components are:
  • Abiotic Component: It is the water that contains all the dissolved organic and inorganic substances along with the rich soil deposits that are present in the bottom portion of the pond.
  • Producers: This includes the autotrophic components that mainly include the phytoplankton, algae along with the floating, marginal and submerged plants that are found at the edges.
  • Decomposers: This group includes the fungi, flagellates and the bacteria which are specifically present abundantly in the bottom of the pond. The pond performs all-important ecosystem functions and also of the biosphere like:
  1. Converts the inorganic into organic material by using the radiant energy of the sun through the autotrophs.
  2. Consumption of autotrophs by the heterotrophs.
  3. Decomposes and mineralisation of the dead matter and releases them back for getting reused by the autotrophs.
  4. There is a single direction movement of the energy towards the high trophic levels and its dissipation and heat loss to the environment.
  • Productivity: One of the most important requirements of the ecosystem to function and survive is the consistent input of solar energy. Some of the important concepts are:
  1. Primary production: It is the total amount of the organic matter or the biomass produced per unit area in a period by the plants through photosynthesis. Primary productivity is based on the kind of plant species that inhabits the particular area, the photosynthetic ability of plants and the availability of nutrients.
  2. The rate of biomass production is called productivity.
  3. Gross primary productivity (GPP): The rate of creation of organic matter during photosynthesis.
  4. Net primary productivity (NPP): This is Gross primary productivity minus respiration losses (R). GPP – R = NPP
  5. Secondary productivity: The rate at which new organic matter is produced by consumers.
  • Decomposition: It is the process of breaking down the complicated organic matter into inorganic substances like carbon dioxide, nutrients and water by the decomposers. Detritus which are the dead plant remains like the leaves, flowers, bark, along with the dead remains of the animals serve as the raw material of the decomposition. They undergo decomposition at a very slow rate. The process of decomposition needs oxygen.

Factors on Which Rate of Decomposition Depends

The chemical composition of detritus. It is slow when it is rich in chitin and lignin and it is quick when it is rich in water-soluble substances like sugars and nitrogen.

Climatic factors: a warm and a moist environment highly suits decomposition and in contrast, a low temperature prevents decomposition. Some of the vital steps n the whole process of decomposition are:

  1. Fragmentation, which is breaking down of the detritus into small particles by the detritivores.
  2. Leaching: A process in which the water-soluble inorganic nutrients get down to the soil horizon and are precipitated as unavailable salts.
  3. Catabolism: Here the bacterial, as well as the fungal enzymes, decomposes the detritus into simple inorganic substances.
  4. Humification: Collection of humus which is a dark coloured amorphous substance. It is highly resistant to microbial action.
  5. Mineralization: it is the process of humus degradation for releasing the inorganic nutrients.

Energy Flow and Food Chain

Every living organism depends on the producers for their food either directly or indirectly. There exists a unidirectional flow of energy starting from the sun to producers and then to the consumers. PAR or photosynthetic active radiation is accountable for food synthesis by the plants. The animals get their food from the pants thus they are called consumers. The whole process of eating and being eaten is known as a food chain. In this food chain, the energy flows from the producers to the consumers. Here is an example of the grazing food chain.

Depending on the food source, every organism dwells in a specific place in the food chain and that is called a trophic level.  In each trophic level, there is a specific mass of living material at a specific time and it is called standing crop. It is calculated as the biomass of living organisms in the unit area.

Ecological Pyramids

It is the graphical representation of the ecological parameter that includes the number, energy and the biomass sequentially in varied trophic levels of a food chain. The producers are present in the base, herbivores in the middle and the carnivores in the top. The pyramid can be either upright, spindle-shaped or inverted.

Ecological Succession 

It is the gradual and predictable alteration in species composition in a given area. At the time of succession, some species colonise an area and then their population becomes more where other populations start declining and sometimes disappear.

This includes primary succession and secondary succession. While the former is a slow process but the later one is a fast process because of the availability of resources.

Nutrient Cycling

The movement of the nutrient elements through several components of an ecosystem is known as nutrient cycling. It is also known as biogeochemical cycles. There are two types of the nutrient cycle: a gaseous cycle that exists in the atmosphere and the sedimentary that exist in the earth crust.

Discussion of Exercises of Xam Idea Class 12 Biology Solutions Chapter 14: Ecosystem

The whole exercise of Xam Idea Class 12 Biology Solutions Chapter 14 consists of 115 questions. It is divided into four important categories: Very short answer type questions, short answer type questions I and II and long answer type of questions. The questions cover all the important concepts of the chapter.

Very Short Answer Type Questions

  • These categories consist of 45 very short questions that need answers in one line. It is further divided into PYQ (past years questions) and OIQ (objective inventory questionnaires).
  •  PYQ consists of 14 questions based on primary productivity, ecological pyramids, primary succession, stratification, and detritivores. 
  • Under the OIQ category, there are 31 questions involving food chain, trophic level, primary productivity, and the pyramid of biomass.

Short Answer Type Questions-I

  • Under this category, there are 33 short answer questions. It is further divided into two categories that are PYQ with 16 questions and OIQ with 17 questions. 
  • The questions are mainly on productivity and their interrelation, importance of decomposers in an ecosystem, constructing a pyramid of biomass and grazing food chain, initiation of primary succession, stratification process, how primary productivity varies from ecosystem to ecosystem.

Short Answer Type Question–II 

  • There are 19 questions under this category and are divided into two categories that are PYQ with 11 questions and OIQ with 8 questions.
  • The questions are mainly like how and where primary succession occurs, length of the food chain, how human activities affect the ecosystem cycle.

Long Answer Type Questions

  • There are 18 long answer type questions. The whole exercise is divided into two subcategories, PYQ with 13 questions and OIQ with 5 questions. 
  • The questions demand descriptive answers and mainly ask about the whole process of decomposition, carbon cycle, the significance of ecological pyramids.

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