ECOSYSTEM 1. SOME IMPORTANT TERMS ECOSYSTEM:- A functional unit of nature where interactions of living organisms with physical environment takes place. STRATIFICATION:- Vertical distribution of different species occupying different levels in an ecosystem. PRIMARY PRODUCTION:- the amount of biomass or organic matter produced per unit area ever a time period by plants during photosynthesis. PRODUCTIVITY:- Rate of production of biomass. GROSS PRIMARY PRODUCTIVITY:- the rate of production of matter during photosynthesis. NET PRIMARY PRODUCTIVITY:- the gross primary productivity minus respiration losses. SECONDARY PRODUCTIVITY:- the rate of formation of new organic matter by consumers. DECOMPOSES:- the organisms that break down complex organic matter into simple substances by acting on dead organisms. DETRITUS:- the remains of the dead plants and animals. LITTER:- the waste that contains paper, dead parts of plants and animals, polythene etc. DETRIVORES:- the organisms which break down detritus into matter particles. FRAGMENTATION:- the process of breaking down of detritus into smaller particles. LEACHING:- The process by which the water soluble inorganic nutrients go down into the soil horizon and get precipitated into unavailable salts. CATABOLISM:- Degradation of complex substances into simple by the action of enzymes. HUMIFICATION:- Formation of humus. MINERALIZATION:- Formation of minerals by the degradation of humus by microbes. PHOTOSYNTHETIOLLY ACTIVE RADIATION:- Solar radiations that are useful for plants for photosynthesis. PRODUCER:- Organisms that produce energy in the ecosystem. CONSUMER:- Organisms that depend on producers for the energy. PRIMARY CONSUMER:- Organisms that directly depend on the producers for energy. SECONDARY CONSUMER:- Organisms that depend on primary consumers for energy. PRIMARY CARNIVORE:- Consumers that feed on herbivores. SECONDARY CARNIVORE:- Consumers that feed on primary carnivore.
SAPROTROPHS:- Organisms that feed on dead organic matter. FOOD CHAIN:- Sequential flow of energy in on ecosystem. FOOD WEB:- interlinked food chains operating in on ecosystem. TROPHIC LEVEL:- Each Step of the food chain. STANDING CROP:- Mass of living material present at a trophic level at a particular time. ECOLOGICAL PYRAMID:- Expression of energy, biomass or number possessed by the different organisms in an ecosystem in a pyramid form. ECOLOGICAL SUCCESSION:- The gradual and fairly predictable change in the species composition of a given area. CLIMAX COMMUNITY:- A community formed during ecological succession that is near to equilibrium with environment. SERE: entire sequence of communities that successively change in a given area resulting in a climax community. PRIMARY SUCCESSION:- Ecological succession that takes place where no living organisms ever existed. SECONDARY SUCCESSION:- Ecological succession that takes place where the life has been totally lost and no organism exist there now. HYDRARCH SUCCESSION:- That takes place in wetter areas. XERARCH SUCCESSION:- That takes place in dry areas. PIONEER SPECIES:- The species that a bare area. STANDING STATE:- Amount of nutrients like carbon, Nitrogen, Phosphorus, calcium etc. present in the soil at any given time. NUTRIENT CYCLING/ BIOGEOCHEMICAL CYCLING:- Movement of nutrient elements through the various components of an ecosystem. GASEOUS CYCLE:- Cycle which have its reservoir of the nutrient. ECOSYSTEM SERVICES:- Products of the ecosystem procures. INVERTED PYRAMID:- ecological pyramid having smaller first trophic level than the second or the base is narrower than the top levels. UPRIGHT PYRAMID:- ecological pyramid having larger trophic level than the second or the base is broader than the top levels. II. IDENTICAL TERMS. Primary productivity / secondary productivity
III. Important Points to Remember Gross primary productivity / net primary productivity Herbivores / carnivores Detrivores / carnivores Detritus/Litter Production / decomposition Fragmentation / leaching Humification / Mineralization Pioneer species / climax species Hydrarch succession / Xerarch succession Primary succession / secondary succession Gaseous cycle / sedimentary cycle Upright Pyramid/Inverted Pyramid Ecosystem is of two types Aquatic & Terrestrial Trees occupy the top level in vertical strata of the Forest Ecosystem, struts occupy second; and herbs and grasses occupy the bottom layers. Grasses occupy the bottom layers. Ecosystem is a self sustainable system. Unit of primary productivity is per gram 2. Unit of productivity is g -2 yr -1 or per g 2 per year. Net Primary Productivity = Grass Primary Productivity Respiration Losses. Primary productivity depends on the plant species inhabiting that area, availability of nutrients and photosynthetic capacity of plants. Oceans have lower productivity than Terrestrial productivity. Decomposition process includes the steps Fragmentation, Leaching, catabolism, Humification and Mineralization. Humus is colloidal in nature and rich in nutrients. Decomposition process requires oxygen. Rate of decomposition depends on the chemical nature of detritus. And temperature. Detritus rich in chitin & lignin decomposes slowly because these substances are very complex in nature. Decomposition process is faster in warm and moist environment than in cold and dry environment Detritus decomposes quicker if it is rich in nitrogen, sugars or water substances. Only 2-10% of PAR is captured by the plants. Energy flow in the ecosystem is unidirectional. Plants and animals in an ecosystem depend on each other, due to this inter dependency the food webs are formed.
Grass Goat Man is the example of Grazing Food chain or GFC. Producers in the Detritus Food Chain or DFC are the decomposers. First trophic level of DFC is dead organic matter. Saprotrophs secrete digestive enzymes that break dawn dead and waste materials into simple, inorganic material. Ten percent law states that only 10% of the energy is transferred to each trophic level from lower trophic level. Trophic level of a food chain represents a functional level. Pyramid of biomass in sea is inverted as the biomass of fish is more than that of phytoplankton. Pyramid of Number in tree ecosystem is inverted as the no. of insects feeding on tree are more. Pyramid of energy is always upright. Change in the diversity of species of organism, increase in the number of species and organisms, and increase in the total biomass takes place in the successive seral stage of ecological succession. Phytoplankton Reed Swamp Stage Submerged Plant Stage Forest Scrub Stage Submerged Free Floating Plant Stage Marsh Meadow stage. Nitrogen & Carbon are the gaseous biogeochemical cycle. Sulphur & Phosphorous cycle are the examples of Sedimentary Cycle. About 4x10 13 Kg of carbon is fixed in the biosphere through photosynthesis annually. Air is the reservoir of Carbon. Processes like Burning of wood, forest fire and combustion of organic matter & fossil fuels; volcanic activities release CO 2 in the air. Rock is reservoir of phosphorous. Purification of air and water, mitigation of droughts and floods, cycling of nutrients, generation of fertile soil providing wild life habitat, maintenance of biodiversity, pollution of crops, providing storage site for carbon and providing of aesthetic, cultural and spiritual values are some of ecosystem services provided by Forest ecosystem.
Important features of Phosphorus cycle/ Sedimentary cycle are Atmospheric inputs of minerals are less. Gaseous exchange between organism and environment is negligible. Rock is the major reservoir. Weathering of Rocks sends the nutrient to the soil. Plants absorb the nutrient from the soil by roots. Nutrient enters into animal body through food. Decomposition of dead plants and animals; and waste material release the element back into the soil. Steps of Phosphorus cycle: Weathering Phosphate Soil Plants Rock Nutrition Soil Decomposition Solution Detritus Animals Steps for Carbon Cycle Photosynthesis CO2 in Air Plants Animals Respiration Chemical Change Slow Slow Chemical Change Fossil Fuels Burning
Lichens are the pioneer species in primary succession of rocks. Lichens secrete acids that weather the soils and helps in soil formation. Lichens Small bryophytes Mosses Herbaceous Plants Are the seral stages of succession on base rock. Forest Trees Shrubs Phytoplankton Free floating angiosperms Trees Grasses Sedges Rooted Hydrophytes Are the seral stages of primary succession in water. Pioneer species in Secondary succession depend on the condition of soil, availability of water and environment, and seral present in the soil. Rate of secondary succession is faster in the secondary succession than the primary succession as soil is already present. One Mark Questions: 1. Name the dominant producers in a aquatic ecosystem. What other name could you give to a primary consumers? Plants, Herbivores. 2. What is meant by saying that the energy flow in an ecosystem is unidirectional? The energy flow in an ecosystem is unidirectional means energy flows in one direction only from producer to consumers and does not come back to source. 3. List two factors that determine the vegetation and soil of an ecosystem. 4. What are the starting points of grazing food chain and detritus food chain? Grass and Detirus respectively. 5. Define Ecosystem. It is a functional unit of nature where interactions of living organisms with physical environment takes place. 6. Name two basic categories of ecosystem. Aquatic and Terrestrial 7. What is meant by species composition of any ecosystem? Species composition means all the plant, animal and microbial species present in an ecosystem 8. Name the basic requirements of any ecosystem to function and sustain? Productivity Decomposition Energy Flow and
Nutrient Cycling 9. What is meant by Productivity? It is the rate of production of biomass. 10. Define secondary Productivity. It is the rate of production of organic matter b the consumers. 11. What is the approximate value of net primary productivity of the Biosphere? 170 billion tons (Dry Weight) 12. What % of Productivity is contributed by Oceans? 55 billion tons 13. What are decomposers? They are the microbes which break down the complex organic matter into simple substances like carbon, nitrogen, water etc. 14. Define Decomposition? It is the Process by which the microbes which break down the complex organic matter into simple substances like carbon, nitrogen, water etc. 15. Name the raw material for decomposition Detritus 16. What is meant by Humification? It is the process of formation of humus. 17. What is meant by PAR? Photosynthetically Active Radiation 18. What are producers in an Eco System? Plants 19. Why is food chain formed in a nature? Food chain is formed because one organism depends on other for food. 20. What are consumers in an eco system? Animals 21. Name the trophic level occupied by a secondary & tertiary consumers. Primary Carnivores and Secondary Carnivores 22. Why is measurement of bio-mass in terms of dry weight more accurate than fresh weight? Measurement of bio-mass in terms of dry weight more accurate than fresh weight because fresh weight contains a large amount of water which decreases due to drying. 23. What is meant by 10% law? It states that only 10% of the energy possessed by a trophic level is transferred to the next trophic level in a food chain. 24. Name the ecological pyramid that is always upright. Pyramid of Energy 25. Name the ecological pyramid that can be inverted in a tree eco-system. Pyramid of Number 26. Why is pyramid of biomass inverted in a water body? Pyramid of Biomass is inverted in a water body because the biomass possessed by fish (Consumer) is larger than the phytoplanktons (producers) 27. Mention one similarity between hydrach & Xerarch succession Both type of succession leads to medium water conditions or mesic conditions i.e. neither too dry nor too wet. 28. Name any two factors on which the type of pioneer species if plant develops in secondary succession. Condition of Soil Availability of water 29. How much of carbon is fixed in the biosphere through photosynthesis annually? 4x10 13 kg 30. How much carbon is dissolved in the Ocean? 71% of global carbon
Two Marks Questions: 1. What does secondary productivity in an ecosystem indicate? List any two factors by which productivity is limited in aquatic eco systems. It is the rate at which the organic matter is formed by the consumers. Two factors that limit the productivity in the aquatic ecosystem are Less Availability of PAR Less availability of dissolved CO 2 for photosynthesis 2. What would happen to the successive trophic level in the pyramid of energy, if the rate of reproduction of Phytoplankton was slowed down? Suggest two factors which could cause such a reduction in Phytoplankton reproduction. They will become narrow. Phytoplankton reproduction is reduced due to: Pollution Eutrophication 3. Name the kinds of organisms which constitute the Pioneer community of Xerarch & Hydrarch successions respectively. In Xerarch Succession, the lichens are the pioneer species whereas in hydrarch succession, it is Phytoplankton 4. What is primary productivity? How it is different from net primary productivity? Primary productivity (PP) is the rate of production of organic matter during photosynthesis whereas Net Primary Productivity (NPP) is the Productivity minus Respiration (R). NPP= PP - R 5. Due to uncontrolled excessive hunting, the population of tigers in a forest becomes zero. Discuss the long term effects of this situation. Number of Deer would increase. They will eat all the grass and land shall become barren; then deer will die due to starvation. 6. List the 3 parameters used for constructing ecological pyramids. Describe any one instance where the pyramid may look inverted. Energy Biomass Number Pyramid of Number may be inverted in a tree ecosystem because the no. of insects feeding on a tree are larger than the tree. 7. What are detritivores? Give an example. The organisms that feed on detritus are known as detritivores. E.g. Earthworm 8. What are Saprotroph? How do they obtain their nutrition? These are the organisms that feed on dead organic matter. They grow on dead organic matter and obtain the food by secreting the enzymes that break down the complex organic matter into simple one which is absorbed by them. 9. Mention the function of reservoir in Nutrient cycling. They act as the storehouses of nutrients and are used to meet the deficit which occurs due to imbalance in the rate of influx and efflux. 10. Differentiate between: i. Primary productivity / secondary productivity ii. Gross primary productivity / net primary productivity iii. Herbivores / carnivores iv. Detritivores / carnivores v. Detritus/Litter
vi. Production / decomposition vii. Fragmentation / leaching viii. Humification / Mineralization ix. Pioneer species / climax species x. Hydrarch succession / Xerarch succession xi. Primary succession / secondary succession xii. Gaseous cycle / sedimentary cycle xiii. Upright Pyramid/Inverted Pyramid 3 Marks Question: 1. What is ecological succession? Explain how it occurs on a bare rock? It is the gradual and fairly predictable change in the species composition of a given area. It occurs in stages. During succession some species invade a bare area known as pioneer species. Lichens are the pioneer species on a bare rock. They grow their and secrete the acid to dissolve rocks. Secretion of acids helps in weathering of rocks and formation of rocks. Spores of the Mosses grow in the soil on the rock formed by the weathering. They are succeeded by the bigger plants and ultimately trees appear after many stages or a climax community is formed. 2. Explain the energy flow in an ecosystem follows laws of thermodynamics. In the ecosystem, the energy flow is unidirectional i.e. from the sun to Producers and then to Consumers; thus it keeps with the first law of thermodynamics. Ecosystems require constant supply of energy as a large amount of energy is lost due to disorderliness (like respiration) in the form of heat. 3. Draw carbon cycle in an ecosystem. Steps for Carbon Cycle Photosynthesis CO 2 in Air Plants Animals Respiration Chemical Change Slow Slow Chemical Change Fossil Fuels Burning
4. How does phosphorus cycle operate in an eco system? Explain with diagram. Phosphorus is a major constituent of cells. It is also required by some animals for the formation of shells, bones, teeth. Its natural reservoir is the phosphate rock. Weathering of phosphate rock sends the phosphorus to the soil and water which are absorbed by the plants. Animals obtain Phosphorus from the plants. Decomposers like phosphate solubilizing bacteria decompose the waste products and the dead organisms and release phosphorus. Steps of Phosphorus cycle: Weathering Phosphate Soil Plants Rock Nutrition Soil Decomposition Solution Detritus Animals 5 Marks Questions: 1. Pond is an eco system. Explain Pond is a self-sustainable unit where the interactions between biotic and abiotic components take place. A pond is a shallow water body in which all the basic components of ecosystem i.e. Productivity, Decomposition, Energy Flow and Nutrient Cycling exist. Water, soil solar radiations, dissolved organic and inorganic substances constitute the abiotic components. Phytoplankton, Algae, Submerged and Marginal plants act as the autotrophs. Zooplankton, free swimming and bottom dwellers act as consumers. Bacteria, fungi and flagellates act as decomposers. This system performs all the functions of the ecosystem. Autotrophs fix solar radiations and synthesize the food; it is consumed by the consumers. Decomposers act on dead aquatic organisms and release the nutrients back into the ecosystem. HOTS Questions: 1. Why is the productivity in oceans lesser than the land? 2. Justify that the energy flow in an ecosystem is unidirectional with an example. 3. Detritus Food Chain and Grazing Food Chain are interconnected at some steps. Explain. 4. Which trophic level is occupied by the human being in different food chains. Explain with examples. 5. Detritus food chain has limited levels. Why? 6. Differentiate between Carbon and Phosphorus Cycle. 7. Why is the rate of Secondary succession faster than Primary Succession?