Class 12 Biology Chapter 14 Ecosystem Solutions to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 14 Ecosystem Question Answer.
Class 12 Biology Chapter 14 Ecosystem
Also, you can read the AHSEC book online in these sections Solutions by Expert Teachers as per AHSEC (CBSE) Book guidelines. These solutions are part of AHSEC All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 14 Ecosystem Solutions for All Subjects, You can practice these here.
Ecosystem
Chapter – 14
ECOLOGY
Very Short Answer Type Questions
Q.1. Many individuals of a species living together in a defined area form ___
Ans : Population.
Q.2. Net primary productivity (NPP) ___ Respiration.
Ans : Gross primary productivity (GPP).
Q.3. Process of breakdown of detritus into smaller particles is called _____
Ans : Fragmentation.
Q.4. _____ is the process by which bacterial and fungal enzymes degrade detritus into simple inorganic substances.
Ans : Catabolism.
Q.5. The mass of living material at a particular time in a trophic level is called _____
Ans : Standing crop.
Q.6. Pyramid of biomass in sea is generally _____
Ans : Inverted.
Q.7. Out of the total cost of various ecosystem services, the soil formation accounts for about_____ per cent.
Ans : 50.
Q.8. Vertical distribution of different species occupying different levels is called _____
Ans : Strata.
Q.9. Of the incident solar radiation (on earth) less than 50% of it is ____
Ans : Utilised (absorbed).
(B). True Or False (1 mark each) :
Q.1. Horizontal distribution of different species’ occupying in different spatial position is called stratification.
Ans : False.
Q.2. Marginal plants are autotrophic components of a pond ecosystem.
Ans : True.
Q.3. Fragmentation, leaching and catabolism during decomposition operate sequentially one after another.
Ans : True.
Q.4. Flow of energy in ecosystem is unidirectional.
Ans : True.
Q.5. Photosynthetic activation radiation constitutes less than 50% of the incident solar radiation.
Ans : True.
Q.6. Grasses, are usually pioneer species in’ primary succession on rocks.
Ans : False.
Q.7. Detritus food chain begins with dead organic matter.
Ans : True.
(C). Very Short Answer Questions: (1 Mark Each)
Q.1. What is ecosystem?
Ans : Ecosystem can be defined as the functional unit of nature where living organisms interact among themselves and also with the surrounding physical environment.
Q.2. What are the two basic categories of ecosystem?
Ans : The two basic categories of ecosystem are Terrestrial and Aquatic.
Q.3. What are the autotrophic components of pond ecosystem?
Ans : The autotrophic components of pond ecosystem are algae including all the green plants.
Q.4. At which part of a pond ecosystem decomposers are abundant?
Ans : Decomposers are abundant in the bottom of the pond.
Q.5. Define gross primary productivity.
Ans : Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.
Q.6. What is net primary productivity?
Ans : The available biomass for the consumption to heterotrophs is known as net primary productivity.
Q.7. Explain the process of leaching during decomposition.
Ans : The process by which water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts is known as leaching.
Q.8. Define mineralization during decomposition.
Ans : The human produced during decomposition is further degraded by some microbes and release of organic nutrients by a process known as mineralization.
Q.9. Which type of food chain is dominant in sea?
Ans : In sea the food chain starts from phytoplanktons to big fishes. So grazing type of food chain is dominant here. Here the pyramid is inverted. Phytoplankton – insects – small fishes – big fishes.
Q.10. How much photosynthetically active radiation (in percentage) is captured by plants?
Ans : 2-10 percent.
Q.11. Except deep sea what is the only energy source for all ecosystems?
Ans : Solar energy.
Q.12. Why measurement of biomass in terms of dry weight is more accurate?
Ans : The biomass when measured in fresh condition it is not accurate because there may contain water and other liquid. substances which can evaporate. So, when the dry weight is taken it is more accurate because there is no chance of evaporation of water.
Q.13. What are green plants known as?
Ans : Green plants are known as producer.
Q.14. What is the role of fungi in an ecosystem?
Ans : Fungi acts as decomposer in an ecosystem.
Q.15. What is trophic level?
Ans : Based on the source of nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level.
Q.16. What is ecological succession?
Ans : The gradual and fairly predictable changes in the species composition of a given area is called ecological succession. It is of two types – Hydrarch and Xerarch.
Q.17. What are the different types of succession?
Ans : There are two main types of succession – Hydarch and Xerarch.
Q.18. What is climax community?
Ans : The climax community is a natural stable community unit which the process of succession goes on. On reaching climax community no further succession occurs in that area until they are destroyed.
Q.19. Why rate of succession is much faster in secondary succession?
Ans : Because, they have more nutrition, and climatic factors.
(D). Short Answer Questions (2 Marks Each) :
Q.1. Define vertical stratification with example.
Ans : Vertical distribution of different species occupying different levels is called vertical stratification. For example – trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layers.
Q.2. State the functional components of ecosystem.
Ans : The functional component of an ecosystem can be divided into two types :
(i) Biotic. And
(ii) Abiotic.
(i) Biotic component : includes air, water, soil.
(ii) Abiotic component : includes producer, consumer and decomposer.
Q.3. What are the different types of primary productivity? State the relation between them.
Ans : There are mainly two types of primary productivity-
(i) Gross primary productivity. and
(ii) Net primary productivity.
Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.
Net primary productivity is the available biomass for the consumption of heterotrophs.
The relation between them is : GPP – R= NPP
Q.4. Why earthworm is called as “Farmer’s Friend”?
Ans : Earthworm is called formers friend because they help in the breakdown of complex organic matter as well as in loosening of the soil.
Q.5. What is the raw material for decomposition called? What are its components?
Ans : The raw material for decomposition is called detritus which constitute dead plant, animal remains such as leaves, bark, flowers and faecal matters etc.
The components of detritus are lignin, chitin, nitrogen, sugars and many water soluble substances etc.
Q.6. What is humus? State its importance.
Ans : Humus is a dark coloured amorphous substance produced as a result of humification during decomposition in the soil and is colloidal in nature.
Humus is very important because it is highly resistant to microbial action and undergoes decomposition at a very slow rate. Due to colloidal in nature it serves as the reservoir of nutrients.
Q.7. State the difference between grazing food chain and detritus food chain.
Ans :
| Grazing food chain | Detritus food chain |
| (i) It starts from the producers. | (i) It starts from the dead organic matter. |
| (ii) These contain both auto- trophs and heterotrophs. Eg. Grass-Deer-Lion | (ii) These contain only heterotroph Eg. Plant lent-Earthworm- Microbes. |
Q.8. Why energy is less at secondary consumer level than the producer?
Ans : The producers accumulate only 10 percent of total energy they receive from sun. In the next level the consumers of the first order utilize this c 8. but they can store only 10 percent of it. So the process continues energy and the energy gets depleted at every level. Hence, it can be said that energy is less at consumer level than the producers.
Q.9. What is food web? How it differs from food chain?
Ans : The natural interconnection of food chains form a food web.
Q.10. What is Standing crop? How it is measured?
Ans : Each trophic level has a certain mass of living material at particular time called as the standing crop. It is measured as the number in a unit.
Q.11. Define 10% law of energy flow. Why the number of levels in a grazing food chain is restricted?
Ans : When we study the trophic levels it is seen that in each higher levels the number of animals or its biomass decreases. It is because the transfer of energy follows 10 percent law that is only 10 percent of the energy is transferred to each trophic level from its lower trophic level. Each trophic level acquires energy from its lower trophic level and 90 percent of that energy it utilized by them and the rest is utilised in respiration. So only 10 percent of the energy remains of the next trophic level and like this in every level 90 percent of the total energy is utilised and 10 percent goes to the higher levels. This is known as 10 percent law of energy flow. For example- the number of trophic levels in the grazing food chain is restricted as the transfer of energy follow 10 percent law.
Q.12. Which type of pyramid is always upright and why?
Ans : In most ecosystems, all the pyramids, of number, of biomass are upright. Here the energy and biomass is more in number at lower trophic levels than the higher.
Q.13. Distinguish between primary and secondary succession.
Ans :
| Primary Succession | Secondary Succession |
| (i) In primary succession, starts in a bare area like bare rocks or in areas that somehow lost all the living organisms that existed there. | (i) In secondary succession, it begins in areas where natural biotic communities have been destroyed such as abandoned form lands, burned of cut for- ests, land that have been flooded. |
| (ii) No living organisms were found found in these areas before the starting of this type of succession. | (ii) Living organisms were in these areas before the starting of these type of community. |
Q.14. Distinguish between hydrarch succession and xerarch succession.
Ans :
| Hydrarch Succession | Xerarch Succession |
| (i) Hydrarch succession takes place in wetter areas. | (i) Xerarch succession takes place in wetter areas. |
| (ii) The successional series pro- gress from hydric to mesopic conditions. | (ii) The series progress from xeric to mesopic conditions. |
Q.15. In a nutshell how can you define Ecosystem services?
Ans : The products of ecosystem processes are named as ecosystem services like healthy forest ecosystems purify air and water, mitigate droughts and floods, cycle nutrients, generate fertile soils, provide wildlife habitat, maintain biodiversity, pollinate crops, provide storage site for carbon and also provide aesthetic, cultural and spiritual values etc.
Q.16. What is a sedimentary cycle?
Ans : Sedimentary cycle is a part of nutrient cycle which include sulphur and phosphorus cycle. Here the reservoir is located in earths crust. Environmental factors soil, moisture, pH, temperature etc. regulate the rate of release of nutrients into the atmosphere.
Q.17. What are different levels of consumers? In grazing food chain what is the position of a goat?
Ans : The different levels of consumers all aA
(a) Primary consumer (herbivorous)
(b) Secondary consumer (Carnivorous)
(c) Tertiary consumer (Top carnivorous)
In grazing food chain the position of goat’s primary consumer a herbivorus.
Q.18. State the factors for invasion of species in secondary succession.
Ans : Invasion involves successful establishment of a species in a bare area it is volves the three steps-
(a) Migration : It involves reaching of seed, spices etc. in a bare atul area through the agencies like air, water etc.
(b) Ecesis : It involves the successful adjustment of a species with h the prevailing conditions of that area.
(c) Aggregation : It involves the increase in member of organisms Innov through the process of reproduction.
(E). Short Answer Question 3 Marks Each :
Q.1. What is productivity? How the productivity of an ecosystem is expressed?
Ans : The rate of biomass production is known as productivity. It is expressed in terms of g²yr¹ or (KCalm²) Yr¹ to compare the productivity of different ecosystems.
Primary productivity 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 (g²) or energy (Kclam²). It can be divided into two types – Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
Gross Primary Productivity (GPP) is the rate of production of organic matter during photosynthesis.
Net Primary Productivity (NPP) is the available biomass for the consumption to heterotrophs. It can be expressed by the following equation – GPP – R = NPP. R = Respiratory Loss.
The rate of formation of new organic matter by consumers is known as Secondary Productivity.
Q.2. Write briefly on the factors controlling primary productivity of ecosystem.
Ans : In an ecosystem green plants are the primary producer. The primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors like solar energy, temperature, animals, soil, other microorganisms present in the atmosphere, availability of nutrients etc. Among these solar energy is the main factor. It is because this is the only source of energy which plants utilise. Without this energy plants cannot survive.
Among the abiotic factors soil, water, temperature, carbon dioxide etc. are very essential for the process of photosynthesis. Moreover, micro-organisms that play an important and great role in the process of primary productivity. Several microorganisms act on the minerals present in the soil and causes cyclical changes in them and transforms them into several essential elements necessary for the growth and development of the plant. Thus the primary. productivity of plants depends on several factors biotic and abiotic factors.
3. Diagrammatically explain decomposition cycle in a terrestrial ecosystem.
Ans : The breakdown of complex organic matter into inorganic matter is called đecomposition which is done by decomposer.
The bit of dead organic remains such as bark, leaves, flowers, fruits, dead remains of the animal and fecal matter present in any ecosystem is known as detritus.
The organisms which feed upon the detritus is called the detritivorous.
All freshly fallen dead plants and animals matter is known as litter. The partially decomposed litter is called duff. Several water soluble inorganic substances percolate into the deeper layers of soil along with rain or irrigation water, it is known as leaching.
The normal biological process of decay by bacteria, fungus etc. results in the formation of finely divided amorphous dark coloured soil with minerals, it is called humus. The process leading to formation of humus is called Humification. The humus further degraded by some microbes and release organic matter and the process is called mineralisation.
Q.4. “Flow of energy in ecosystem follows the laws of thermodynamics”, explain the statement.
Ans : Energy flow is passage or flow of energy from one trophic level to another trophic level and is unidirectional.
(i) Capture of energy : Sun is the only source of energy for all ecosystems on earth. Out of the total incident solar radiation, only 50 percent is photosynthetically active radiation (PAR). Plants capture 2-10 percent of the PAR to form organic matter. The net primary productivity is available to the rest of the ecosystem.
(ii) Passage of herbivores : Herbivores are dependent for their food on producers. In addition to organic matter or food, its contained energy becomes available to herbivores. However, only 10% of energy is stored in herbivore biomass. The remaining being lost to decomposers or waste organic matter or dissipated as heat.
(iii) Passage to primary carnivores : Only 10 percent of herbivores biomass energy is used by primary carnivores. The remaining dissipated as heat, lost to decomposers.
(iv) Passage secondary carnivores : Only 10 percent of the biomass energy available at the previous trophic level (primary carnivores) is available to the secondary carnivores.
(v) converted into dead biomass that serves as an energy source of Energy of decomposes : The utilised net primary production is decomposers.
Q.5. What is food chain? Describe the two basic types of food chain with examples.
Ans : In an ecosystem generally sun is the only source of energy. The autotrophs like plants etc. fix the sun radiant energy, to make food from simple inorganic materials and convert it into chemical energy. All organisms are dependent for their food on plants directly or indirectly. So animals i.e. herbivores feed on plants and these herbivores are eaten by the carnivores form a food chain.
The energy trapped by the producer hence is passed on to the primary consumer and then to the secondary consumer. Ultimately this energy goes to the decomposers. The food chain or web formed is due to this interdependency of organisms. There are mainly two basic types of food chains Grazing Food Chain.
(i) Grazing Food Chain (GFC) : This type of food chain starts at the producer level and completes at the decomposer level. This type of food chains have so many levels like- producer, herbivore, carnivore and at last the decomposers. Here in each level 90 percent of the total energy is consumed. For example : Grass – Deer- Tiger.
(ii) Detritus Food Chain (DFC) : It begins with dead organic matter. It is made up of decomposers which are heterotrophic like fungi and bacteria. They meet their energy requirements by degrading detritus, with the help of some digestive enzymes secreted by them, into simple inorganic materials which are subsequently absorbed by them.
Q.6. Where do you get inverted pyramid? Describe briefly an inverted pyramid of number.
Ans : Generally, almost all the pyramids found in ecosystem are upright but there are exception.
The pyramid of biomass in sea is inverted because the biomass of fishes for exceeds that of phytoplankton. In general producers are more in number and biomass than the herbivores and herbivores are more in number and o energy at lower trophic level is always biomass than the carnivores. Also. more than at a higher level.
But the number of insects feeding on a big tree is less than the number of birds feeding on the insects. Similarly the number of birds feeding on the insect eating small birds are more in number. So depending on this if a pyramid is made it will form an inverted pyramid.
| Sl. No. | CONTENTS |
| Chapter 1 | Reproduction in Organisms |
| Chapter 2 | Sexual Reproduction in Flowering Plants |
| Chapter 3 | Human Reproduction |
| Chapter 4 | Reproductive Health |
| Chapter 5 | Principles of Inheritance and Variation |
| Chapter 6 | Molecular Basis of Inheritance |
| Chapter 7 | Evolution |
| Chapter 8 | Human Health and Disease |
| Chapter 9 | Strategies for Enhancement in Food Production |
| Chapter 10 | Microbes in Human Welfare |
| Chapter 11 | Biotechnology: Principles And Processes |
| Chapter 12 | Biotechnology and its Applications |
| Chapter 13 | Organisms and Populations |
| Chapter 14 | Ecosystem |
| Chapter 15 | Biodiversity and Conservation |
| Chapter 16 | Bioresources of Assam |
| Chapter 17 | Environmental Issues |
Q.7. Describe the primary succession in water.
Ans : In primary succession in water the pioneer species are the small phytoplanktons. During the course of time they are replaces by free floating angiosperms then by rooted hydrophytes, sedges, grasses and finally the trees. The climax community formed as a result of this succession in a forest. With the time the water body is converted into land.
Q.8. Explain the carbon cycle.
Ans : After water, carbon constitute 49 percent of dry weight of organism. Carbon dioxide is the principal source of inorganic carbon for all organisms. Green plants absorb this gas and through a complex process convert it into carbohydrate. Hěterotrophs utilise this carbohydrate as food and convert it into other forms of complex organic compounds. During the process of breaking down of food in the body of heterotrophs carbon dioxide is liberated which goes back into the atmosphere. Decomposers also contribute substantially to carbon dioxide pool by their processing of waste materials or dead organic matter of land or oceans. Some amount of the fixed carbon is lost to sediments and removed from circulation. Burning of wood, forest fire, volcanic activity has significantly increase the rate of releąse of carbon dioxide. Thus carbon dioxide circulates from inorganic state (atmosphere) to organic state (timing organism) and returns to the inorganic state again for reuse.
Q.9. What is nutrient cycling? What are the different types of nutrient cycling? Give one example of each of them.
Ans : Nutrients are never lost from the ecosystems. They are recycled i.e. they circulate in the biosphere in circular path entering into the living system by converting themselves as organic compounds and then on death of the organisms the organic compounds are mineralised to return the elements into the environments. So, the movement of nutrient elements through the various components of an ecosystem is called nutrient cycling. It is also known as biogeochemical cycle.
Nutrient cycles are of two types :
(a) Gaseous. and
(b) Sedimentary.
(a) Gaseous Cycle : The reservoir of gaseous type of nutrient cycle (v) like – nitrogen cycle, carbon cycle exist in the atmosphere.
(b) Sedimentary Cycle : For Sedimentary cycle like- Sulphur cycle and phosphorus cycle the reservoir is located in earth’s crust.
Q.10. Describe the phosphorus cycle.
Ans : Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer system of organisms. The natural reservoir of phosphorus is rock which contain phosphorus in the form of phosphates. When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants. Herbivores and other elements obtain this element from plants. The waste products and dead organisms are decomposed by phosphate solubilizing bacteria releasing phosphorus. Atmospheric insect of phosphorus through rainfall are much smaller than carbon cycle and gaseous exchange of phosphorus between organism and environment are also negligible.
Q.11. Write briefly on ecosystem services.
Ans : From the beginning man has been dependent on nature for his existence. The nature has been kind enough to provide him healthy air, water, good soil, fibres, wood, energy resources and many more. Besides these, ecosystems provide suitable habitats for wild life, have mechanisms for regenerating fertile soils, mitigate the effects of pollution, recycle the minerals so that they are available to the organisms for their healthy growth and development. All the above benefits that we get from the ecosystem are referred to as ecosystem services. We get them free of cost in the ecosystem, and therefore, as human nature is, we have exploited them without considering the need and importance of their preservation.
(F). Long Answer Question (5 Marks Each)
Q.1. Why is the pond regarded as a classic example of ecosystem? Explain pond as an example of ecosystem.
Ans : A pond represents a perfect ecosystem. Producers, consumers and decomposers are all present in the pond. All inorganic substances which support the producers are also available in a pond. The major component of a pond ecosystem can be divided into two types-
(a) Abiotic component. and
(b) Biotic component.
(i) Abiotic Component : The sunlight, water, oxygen, carbon dioxide and minerals such as nitrogen, phosphorus, sulphur, calcium etc. represent abiotic substances available in a pond. Various cyclic process like carbon cycle, oxygen cycle, nitrogen cycle etc. continue in the pond ecosystem which help to maintain link between abiotic and biotic components.
(ii) Biotic Components : It can be divided into –
(a) Producers : The major producers in a pond ecosystem is represented by phytoplanktons like chlamydomonas. Euglena, rudorina etc. which produces food. These converts solar energy to chemical energy.
(b) Consumers :
(i) The primary consumers are represented by minute floating zooplanktons like water fleas, nymphs and larvae of insects etc.
(ii) The secondary consumers include crustaceans, rotifers, small fishes etc.
(iii) The top carnivores are represented by large fishes, fish eating birds, crocodiles etc.
(c) Decomposers : The decomposers are the various types of microorganisms and the detritus animals like protozoa etc. living in mud near or bottom of the pond and break down the organic matter. im From the above description it is evident that the food chain starting from the producer runs through various trophic levels. In this way a pond represents a classic example of ecosystem.
Q.2. What is decomposition? Explain the process of decomposition.
Ans : The process of breaking down of complex organic matter into inorganic matter or substances like carbon dioxide, water and nutrients is known as decomposition.
The raw materials for the process of decomposition includes dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter also known as detritus. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation.
Detritivores like earthworm break down detritus into smaller particles by a process known as fragmentation.
Leaching leads water soluble inorganic nutrients to go down into the soil horizon and get precipitated as unavailable salts.
Bacterial and fungal enzymes degrade detritus into simpler inorganic substances by the process of catabolism.
Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of dark coloured amorphous substance called humus which in nature serves as reservoir of nutrients. This humus is further degraded by some microbes and release of inorganic nutrient occur by a process which is known as mineralisation.
Decomposition is largely an oxygen requiring process the rate of which is controlled by chemical composition of detritus and climatic factors. Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.
Q.3. How energy flow occurs in an ecosystem? Depict the energy flow through necessary diagrammatic representation.
Ans : Sun is the only source of energy for all ecosystems on Earth. Plants fix this solar energy to make food and all organisms are dependent on plant directly or indirectly. So here the flow of energy occurs from the source of plants, then plants to consumers and after this to the consumers. This is known as energy flow in ecosystem.
The dimension of energy flow in an ecosystem depends on some features :
(i) Sun is the source of all energy : The solar energy is transformed to light energy, chemical energy and heat energy. The green plants absorb light energy which is transformed to chemical energy and producers to consumers and then to the decomposers. Only 1-5 percent of the total light energy falling on plants is used for photosynthesis.
(ii) Energy flow in ecosystem follows the laws of Thermo dynamics : The fixation and utilization of solar energy by the green plants in the form of food obey two laws of Thermodynámics-
According to the first law of thermodynamics energy cannot be created or destroyed. It can only be transformed from one form to another.
The second law of thermodynamics states that every transformation of energy is accompanied by a simultaneous degradation of energy from concentrated form to dispersed form. That is at each step of conversion some energy is lost as heat energy.
The potential energy used by producers and consumers for metabolic lurks is transformed into heat energy.
(iii) Unilateral flow of energy and its stepwise degradation: After the conversion of solar energy by producers and consumers in different forms it cannot return the solar energy. Hence it can be said that the energy once acquired cannot be sent back to its source again. The flow of energy is unidirectional.
The green plants conserves only 10 present of the total solar energy it receives as net primary production and the rest is lost as heat energy. The primary,net production is used by consumer but 90 percent of it is lost again as heat energy and 10 percent is incorporated in the body of the primary consumer as net energy. Thus in the successive levels the energy available goes on decreasing.
The energy accumulation in various trophic level may be illustrated as follows :
Producers – First level – Second level – Third level
consumers consumers consumers
1000 KCal → 100 KCal : 10K Cal : 1KCal
This may form a pyramid of energy.
Q.4. What do you mean by an Ecosystem? Describe the different components of an Ecosystem.
Ans : A natural unit comprising of living and non-living components, interacting and exchanging materials between them forms a self-dependent and adaptable system known as ecological system or ecosystem.
The main components of an ecosystem can be classified as :
(i) Biotic : Includes all the living organisms.
(ii) Abiotic : Includes all the nonliving components of an ecosystem.
(iii) Biotic component : These are as follows :
(a) Producers : These are the green plants which trap solar and convert it to potential chemical energy. These are also known as autotrophs.
(b) Consumers : All animals and non-green plants which directly or indirectly depend upon the producers for energy from the food.
(c) Decomposers : These include all micro-organisms which cause decomposition of the dead remains of the plants and animals and utilise a part of the product of decomposition and release the rest of it for use by the producers. Here the decomposers decomposes organic substances to simpler inorganic form.
(ii) Abiotic factors : The major abiotic factors of an ecosystem includes air, water, soil, light, temperature.
(a) Air : Air is essential part of an ecosystem. Air means O₂ CO₂, N₂ and other essential components for life. Air should be pure.
(b) Water : Water is the major constituent of supporter of protoplasm and in an ecosystem water may be present in liquid, vapour and in solid form.
(c) Light : Light is another limiting factor of an ecosystem. It is essential for the growth, development and for the distribution of some animals and plants.
(d) Temperature : It is also most essential regulating factor for plants and animals in an ecosystem.
Q.5. What is ecological pyramid? Explain different types of pyramids with necessary diagrams.
Ans : The interrelationship between the successive food levels may be expressed in terms of number of individuals, biomass, energy flow etc. In graphical form called ecological pyramid.
The ecological pyramids are of 3 types :
(a) Pyramid of number.
(b) Pyramid of energy.
(c) Pyramid of biomass.
(a) Pyramid of number : It is the graphic representation of the number of individual organisms in different trophic levels of a food chain.
The pyramid of number may be upright as shown or it may be inverted as in a tree ecosystem. In a tree ecosystem, the producer is represented by the single tree.A number of insects inhabit the tree and derive their nutrition from these. A good number of birds feed on the insects.
(b) Pyramid of energy : In terms of energy, the base i.e. producers contains maximum and it is gradually reduces from producer level to decomposer level. It follows the 10 percent law. Only 10 percent of energy is flowing from one trophic level to the next. In this way a upright pyramid is formed.
(c) Pyramid of Biomass : Energy from food received from the lower trophic level is conserved as biomass which in turn eaten by the organisms of the next higher trophic level. It is, therefore, the biomass of all individuals. of the trophic level. Consequently, the number of individuals decreases. It may be inverted pyramid.
Q.6. Explain in brief the process of ecological succession bare rocks.
Ans : On a baren rock, the primary succession results the invading of the pioneer species which are lichens. The lichen are called the primary succession. Over the lichen, bryophytes and then forms and then other trees are growing resulting climax community. The formation climax community i.e. forest in a baren rock iş called ecological succession. The rock i.e. xerophytic habitat is now getting converted into the mesophytic environment.
Q.7. Write about the ecosystem services.
Ans : A wide range of economic, environmental and aesthetic benefits provided to the human beings by ecological processes of an ecosystem are collectively called ecosystem services.
Services of a healthy forest ecosystem :
(i) Forest provides food in the form of root, tuber, leaves, fruits etc.
(ii) Forest provides fuel in the form of wood for cooking and keeping warm.
(iii) Forest provides timber for building purposes of house, ship, railway, sleeper, sport items etc.
(iv) Forest also provides a number of useful products like camphor, essential oils, tennis, dyes, gums, resins, soap, drugs etc.
(v) These keep the environment cool by regulating the transpiration and precipitation.
(vi) These provides shelter to a variéty of animals.
(vii) They produce more oxygen the other organisms by the process of photosynthesis.
(viii) These prevent roil erosion and helps in soil conservation.
Give One Word Technical Term: (Special 1 Mark Questions)
Q.1. Group of organisms of one species occupying a definite area.
Ans : Community.
Q.2. A group of organisms belonging to a number of different species.
Ans : Population.
Q.3. A community of organisms, their physical environment interacting as a unit.
Ans : Ecosystem.
Q.4. Green photosynthetic organisms forming the first trophic level.
Ans : Producer.
Q.5. The stored plant energy after respiratory utilization.
Ans : Net Primary Productivity.
Q.6. A series of eating and being eaten.
Ans : Food chain.
Q.7. Network formed by interacting food chains.
Ans : Food.
Q.8. Total mass of organisms- fresh or dry weight.
Ans : Biomass.
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