Case Study Questions Class 12 Biology Chapter 14 Ecosystem
CBSE Class 12 Case Study Questions Biology Ecosystem. Term 2 Important Case Study Questions for Class 12 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Ecosystem.
At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.
CBSE Case Study Questions Class 12 Biology Ecosystem
Case study 1
Interaction of biotic and abiotic components result in a physical structure that is characteristic for each type of ecosystem. Identification and enumeration of plant and animal species of an ecosystem gives its species composition. Vertical distribution of different species occupying different levels is called stratification. For example, trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layers. The components of the ecosystem are seen to function as a unit when you consider the following aspects: (i) Productivity; (ii) Decomposition; (iii) Energy flow; and (iv) Nutrient cycling. To understand the ethos of an aquatic ecosystem let us take a small pond as an example. This is fairly a self-sustainable unit and rather simple example that explain even the complex interactions that exist in an aquatic ecosystem. A pond is a shallow water body in which all the above mentioned four basic components of an ecosystem are well exhibited. The abiotic component is the water with all the dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond. The solar input, the cycle of temperature, day-length and other climatic conditions regulate the rate of function of the entire pond. The autotrophic components include the phytoplankton, some algae and the floating, submerged and marginal plants found at the edges.
The consumers are represented by the zooplankton, the free swimming and bottom dwelling forms. The decomposers are the fungi, bacteria and flagellates especially abundant in the bottom of the pond. This system performs all the functions of any ecosystem and of the biosphere as a whole, i.e., conversion of inorganic into organic material with the help of the radiant energy of the sun by the autotrophs; consumption of the autotrophs by heterotrophs; decomposition and mineralisation of the dead matter to release them back for reuse by the autotrophs, these event are repeated over and over again. There is unidirectional movement of energy towards the higher trophic levels and its dissipation and loss as heat to the environment.
Que. 1) Autotrophs consumption in the ecosystem occurs by …………………………………………………………………………………….
(a) Decomposers
(b) Autotrophs
(c) Heterotrophs
(d) Herbivores
Que. 2)…………………………………………………………………… are represented as a consumer.
(a) Zooplanktons
(b) Fungi
(c) Flagellated
(d) Algae
Que. 3) Components of ecosystem include ………………………………………………………………………………….
(a) Kreb cycle
(b) Glucose cycle
(c) Cell cycle
(d) Nutrient cycle
Que. 4) Write definition of ‘Stratification’ and give one example of it.
Que. 5) Which decomposers are important to function ecosystem?
Answer Key
Que. 1)(c) Heterotrophs.
Que. 2) (a) Zooplanktons.
Que. 3) (d) Nutrient cycle.
Que. 4) Answer: Different levels which are occupied by vertical distribution of different species, this is called as Stratification. In the forest, trees occupy top layer and grasses occupy bottom layer. This is an example of Stratification.
Que. 5) Answer: Decomposers such as flagellated, bacteria and fungi are import to function ecosystem.
Case study 2
A constant input of solar energy is the basic requirement for any ecosystem to function and sustain. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (gm–2 ) or energy (kcal m–2 ). The rate of biomass production is called productivity. It is expressed in terms of gm–2 yr –1 or (kcal m–2) yr –1 to compare the productivity of different ecosystems. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP). GPP – R = NPP Net primary productivity is the available biomass for the consumption to heterotrophs (herbiviores and decomposers). Secondary productivity is defined as the rate of formation of new organic matter by consumers. Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants. Therefore, it varies in different types of ecosystems. The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter. Of this, despite occupying about 70 per cent of the surface, the productivity of the oceans are only 55 billion tons. Rest of course, is on land.
Que. 1) In the ecosystem, the …………………………………………………………………………………. is expressed in terms of gm-2 yr-1.
(a) Energy flow
(b) Productivity
(c) Decomposition
(d) Cycle of nutrients
Que. 2) Complete the following equation of Net primary productivity.
NPP= GPP ___ _______.
(a) + P
(b) +R
(c) -P
(d) -R
Que. 3) Productivity is defined as the rate of …………………………………………………………………………….. production.
(a) Net primary
(b) Biomass
(c) Inorganic matter
(d) All of them
Que. 4) Explain the factors on which primary productivity is dependent?
Que. 5) Define ‘Gross primary productivity’.
Answer Key
Que. 1)(b) Productivity
Que. 2) (d) –R.
Que. 3) (b) Biomass.
Que. 4) Answer: Availability of nutrients, environmental factors, plant species, and photosynthetic capacity of plants these are the factors on which primary productivity is dependent.
Que. 5) Answer: Gross primary productivity- During photosynthesis process, the rate of production of organic matter is called as GPP or Gross primary productivity.
Case study 3
You may have heard of the earthworm being referred to as the farmer’s ‘friend’. This is so because they help in the breakdown of complex organic matter as well as in loosening of the soil. Similarly, decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition. Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation. Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation. By the process of leaching, watersoluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism. It is important to note that all the above steps in decomposition operate simultaneously on the detritus (Figure 14.1). Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation. Decomposition is largely an oxygen-requiring process.
The rate of decomposition is controlled by chemical composition of detritus and climatic factors. In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars. Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build-up of organic materials.
Que. 1) Which of the following is a raw material for decomposition?
(a) Leaves
(b) Dead Plant
(c) Flowers
(d) Animals
Que. 2) When water soluble inorganic nutrients goes down in the soil and precipitated as unavailable salts, then the process is called as ……………………………………………………………………………………….
(a) Catabolism
(b) Fermentation
(c) Humification
(d) Leaching
Que. 3) ……………..……………………………………………………… is required in the decomposition process.
(a) Oxygen
(b) Phosphorous
(c) Zinc
(d) Nitrogen
Que. 4) What is meant by catabolism?
Que. 5) Write a very short note on Mineralisation from above paragraph.
Answer Key
Que. 1)(b) Dead Plant.
Que. 2) (d) Leaching.
Que. 3) (a) Oxygen.
Que. 4) Answer: When the fungal and bacterial enzymes degrade detritus and convert it into simpler inorganic substance, then it is called as Catabolism.
Que. 5) Answer: In this process, some microbes degrade humus. The inorganic nutrients are released by the process and the process is known as Mineralisation.
Case study 4
Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials. Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world. So, it is very important to know how the solar energy captured by plants flows through different organisms of an ecosystem. All organisms are dependent for their food on producers, either directly or indirectly. The green plant in the ecosystem are called producers. In a terrestrial ecosystem, major producers are herbaceous and woody plants. Likewise, producers in an aquatic ecosystem are various species like phytoplankton, algae and higher plants. You have read about the food chains and webs that exist in nature. Starting from the plants (or producers) food chains or rather webs are formed such that an animal feeds on a plant or on another animal and in turn is food for another. The chain or web is formed because of this interdependency. No energy that is trapped into an organism remains in it for ever. The energy trapped by the producer, hence, is either passed on to a consumer or the organism dies. Death of organism is the beginning of the detritus food chain/web. All animals depend on plants (directly or indirectly) for their food needs.
They are hence called consumers and also heterotrophs. If they feed on the producers, the plants, they are called primary consumers, and if the animals eat other animals which in turn eat the plants (or their produce) they are called secondary consumers. Likewise, you could have tertiary consumers too. Obviously the primary consumers will be herbivores. Some common herbivores are insects, birds and mammals in terrestrial ecosystem and molluscs in aquatic ecosystem.
Que. 1) ………………………………………………………………………. Is an herbivore organism in the aquatic ecosystem.
(a) Molluscs
(b) Insects
(c) Mammals
(d) Birds
Que. 2) In the ecosystem, green plants are ……………………………………………………………………………………….
(a) Consumers
(b) Decomposers
(c) Producers
(d) All of them
Que. 3) PAR is a …………………………………….……………………………….
(a) Powerful Atomic Radiation.
(b) Photosynthetically Atomic Radiation.
(c) Photosynthetically Active Radiation.
(d) Powerful Active Radiation.
Que. 4) Which ecosystem on earth does not require sun as an energy source?
Que. 5) Name any two producers from aquatic ecosystem.
Answer Key
Que. 1)(a) Molluscs.
Que. 2) (c) Producers.
Que. 3) (c) Photosynthetically Active Radiation.
Que. 4) Answer: The deep sea hydro-thermal ecosystem is the ecosystem on earth that does not require sun as an energy source.
Que. 5) Answer: Algae and phytoplankton both are producers in an aquatic ecosystem.
Case study 5
The consumers that feed on these herbivores are carnivores, or more correctly primary carnivores (though secondary consumers). Those animals that depend on the primary carnivores for food are labelled secondary carnivores. A simple grazing food chain (GFC) is depicted below:
Grass |
Goat | Man |
Producer | Primary consumer |
Secondary consumer |
The detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus. These are also known as saprotrophs (sapro: to decompose). Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them. In an aquatic ecosystem, GFC is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC. Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web. How would you classify human beings!
Que. 1) ………………………………………………………………………….. is a beginning of Detritus food chain.
(a) Living organic matter
(b) Producers
(c) Dead organic matter
(d) Consumers
Que. 2) The meaning of sapro word in the saprotrophs is ………………………………………………………………………………………….
(a) To produce
(b) To divide
(c) To consume
(d) To decompose
Que. 3) GFC is a ………………………………………………………………………..
(a) Global food chain
(b) Grazing food chain
(c) Global food consumers
(d) Grazing form chain
Que. 4) Write a short note on Grazing food chain.
Que. 5) What is ‘Food web’.
Answer Key
Que. 1)(c) Dead organic matter.
Que. 2) (d) To decompose.
Que. 3) (b) Grazing food chain.
Que. 4) Answer: The producers are present in beginning of grazing food chain. Grass is taken as producer in this chain. Then goat is primary consumer because it eats or consume grass. Man are secondary consumers in the chain because man consume goat which consumes grass.
Que. 5) Answer: The normal interconnection of food chain is known as Food web.
Case study 6
An important characteristic of all communities is that their composition and structure constantly change in response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession some species colonise an area and their population become more numerous whereas populations of other species decline and even disappear. The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities.
In the successive seral stages there is a change in the diversity of species of organisms, increase in the number of species and organisms as well as an increase in the total biomass. The present day communities in the world have come to be because of succession that has occurred over millions of years since life started on earth. Actually succession and evolution would have been parallel processes at that time.Examples of areas where primary succession occurs are newly cooled lava, bare rock, newly created pond or reservoir. The establishment of a new biotic community is generally slow. Before a biotic community of diverse organisms can become established, there must be soil. Depending mostly on the climate, it takes natural processes several hundred to several thousand years to produce fertile soil on bare rock.
Secondary succession begins in areas where natural biotic communities have been destroyed such as in abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession.
Que. 1) A succeseful change of entire sequence of communities in a given area is known as …………………………………………………………………………………….
(a) Ecological succession
(b) Sere
(c) Ecology
(d) Community
Que. 2) In a given area, when species composition predictably changes then it is a ………………………………………………………………………………….
(a) Sere
(b) Climax community
(c) Climax changes
(d) Ecological succession
Que. 3) …………………………………………………………………… is the area where secondary succession begins.
(a) Cut forests
(b) Cooled lava
(c) New pond
(d) Bare rock
Que. 4) Give an example of area where primary succession occurs.
Que. 5) Where does secondary succession begins?
Answer Key
Que. 1)(b) Sere
Que. 2) (a) Cut forests.
Que. 3) (d) Ecological succession.
Que. 4) Answer: Primary succession mainly occurs in the area such as bare rock, newly created ponds and newly cooled lava.
Que. 5) Answer: The natural biotic communities were destroyed in an area. From that area secondary succession begins.