Notes to Teachers • Learning Objectives: 1. The meaning of the terms: species, population, community, habitat, ecosystem and biosphere (0.5 hr) 2. The concepts of food chain, food web, the pyramid of 2009 IJSO BIOLOGY number, pyramid of biomass and pyramid of energy the transfer of energy between different trophic levels Cycles in Nature and its relative efficiency; the importance of producers, consumers and decomposers in the cycling of nutrients (2.5 hrs) 3. The water, nitrogen and carbon cycles (1 hr) 4. The roles of decomposers and scavengers (0.5 hr) 1. Time Allocation: 4.5 hrs
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Learning Outcomes Learning Outcomes • Students should be able to: • Students should be able to: 1. define species, population, community, habitat, 6. explain the roles of producers, consumers and ecosystem and biosphere and describe their decomposers in the cycling of nutrients; interrelationship; 7. state the major stages of the water, nitrogen and carbon 2. draw food chain, food web, the pyramid of number, cycles; pyramid of biomass and pyramid of energy; 8. evaluate the importance of the nitrogen and carbon 3. explain the flow of energy within an ecosystem; cycles; 4. assess the efficiency of energy transfer between trophic 9. develop an awareness of the effects of human levels; interference on the nitrogen and carbon cycles; and 5. relate the concept of energy flow between different 10. distinguish decomposers and scavengers. trophic levels to photosynthesis, respiration and chemosynthesis;
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Cycles Ice / Water / water vapour
Water cycle a b Gases (O2 and CO2 ) cycle Ice Water Water Carbon cycle vapour Nitrogen cycle d c e condensation / sublimation / freezing evaporation / melting
5 6 Evapotranspiration = Water Cycle Evaporation + transpiration
7 8 http://ga.water.usgs.gov/edu/watercycleprint.ht ml
Experiment to demonstrate transpiration Gases cycle Carbon dioxide + water What can you observe?
Respiration photosynthesis
bell jar potted plant potted Carbon compound e.g. starch plant plastic without + Oxygen bag stem and leaves
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Ecosystem • Some terms: species / population / community / habitat / physical (abiotic factors) / biotic factors / ecosystem plant community
population B
A animal community
C
microorganism community
11 12 Natural ecosystem Artificial ecosystem – aquarium
tropical rain forest
coral reef
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Mode of nutrition Organism Mode of nutrition? Carbon source simple inorganic compound organic compound • 1.human? e.g. CO2 , H2 S e.g. carbohydrate (autotrophic nutrition) (heterotrophic nutrition) • 2.tapeworm? (絛蟲) Energy source light energy chemical energy chemical energy (photosynthesis) (chemosynthesis) • 3.mushroom? (菇)
dead organic matter food living host • 4.pitcher plant? • (need digestion) (need ingestion) (need not digestion) • & digestion • (saprophytic (holozoic nutrition) (parasitic • nutrition) 動物式營養 nutrition)
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Pitcher plant – insectivorous plants Biotic components of an ecosystem 1.Producers e.g. green plants, grass, algae, phytoplankton浮游植物
2.Consumers (primary/secondary/tertiary…/top)
3.Decomposers (saprophytic bacteria and fungi) break down dead bodies, faeces and excretory wastes into inorganic minerals which can be released to soil and absorbed by the producers. They help the recycling of materials in the ecosystem.
17 18 Decomposers saprophytic fungi) Saprophytic fungi – bread mold
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Decomposers saprophytic fungi Food Chain mushroom • Transfer of materials and energy from plants to organisms
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Food Web
23 24 Trophic levels (食性層次) Food Web in Grassland Write down one food chain which involves 5 organisms. Trophic level ( one specific food chain) Organism fifth trophic level / quarternary consumer ? fourth trophic level / tertiary consumer ? third trophic level / secondary consumer ?
second trophic level / primary consumer ?
first trophic level / producer ?
25 26 http://teacherweb.com/NF/StPetersJuniorHigh/MrGWilliams/photo3.stm
Energy flow and energy loss Energy flow and energy loss producers capture the light energy by photosynthesis and convert it into chemical energy stored in organic food. lose energy in three ways: (i) their own respiration as heat (ii) being eaten by consumers (iii) being decomposed by decomposer when death.
chemical energy flows by feeding.
chemical energy stored in organic food released in cellular respiration in form of ATP
consumers at different trophic levels lose energy by the similar ways: respiration as heat / death / excretion. 27 28
Pyramid of Pyramid of number number/biomass/energy (i) energy loss due to respiration as heat / death / excretion, less energy can only support a smaller number of organisms.
à the number of organisms decreases along the trophic level, pyramid of number is an upright triangle
29 30 Inverted pyramid of number Different shapes of e.g. (i) the producer is very large but no. is small pyramid of number (ii) consumers are parasites, small but many
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Pyramid of biomass . Inverted pyramid of biomass . Biomass amount of living materials in Producers might be few or small, but organisms at each trophic level per unit reproduced at a massive rate to feed the area at any one time. larger number of grazing consumers.
e.g.: At grassland – the food chain in a fertile, productive field which is being constantly grazing by cows. At ocean phytoplankton reproduced at a massive rate to feed zooplankton.
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Inverted pyramid of biomass Fertile and Inverted pyramid of biomass productive field : sheep graze on grass
35 36 Pyramid of energy Material flow within an ecosystem
always in an upright position due to energy loss along food chain
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Carbon Cycle human activities that disturb carbon cycle 1. Overconsumption of fossil fuels
39 40 http://www.epa.gov/maia/html/nitrogen.html
human activities that disturb Greenhouse effect 溫室效應 carbon cycle 2. Deforestation
41 42 Nitrogen Cycle
5.absorption
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root nodules of leguminous plants Nitrogen cycle (symbiotic / mutualistic nitrogenfixing bacteria) • Plants absorbs N in form of nitrate (NO 3 ) • N is important for protein synthesis • 1.lightning N 2 > NO 3 2.nitrogen fixation (固氮作用) by nitrogenfixing bacteria
N 2 > nitrogenous compound e.g amino acid 3. decomposition / industrial synthesis of fertilizers nitrification (硝化作用) by nitrifying bacteria + > NH 3 > NH 4 > NO 2 NO 3
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pH change Enhance crop productivity by + NH3 NH4 NO 2 NO3 (i) Adding chemical fertilizer +H H +O (ii) Adding organic fertilizer +O (iii) Crop rotation Oxidation – H+ release > pH reduces (acidic) (iv) Burning aerial portions of plants Conditions favourable for processes in nitrogen cycle and incorporating the ashes in soil aerobic condition is favourable for nitrification. (v) Deep ploughing anaerobic condition e.g. waterlogging (水浸) is favourable for denitrification.
47 48 Human activities that disturb Scavengers N cycle Scavengers animals that consume (i) Deforestation already dead animals (ii) Overhunting e.g. vultures, burying beetles, blowflies, (iii) Release of a large amount of nitrogen dung beetles and raccoons. oxides e.g. NO 2 into the atmosphere by vehicles The remains left by scavengers will be decomposed by the decomposers. (iv) Excessive use of chemical fertilizer Eutrophication(富養化作用) e.g. algal bloom (red tide)
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Eutrophication(富養化作用) Decomposers e.g. algal bloom 藻華 (red tide) saprophytic fungi and bacteria (not parasitic – disease causing) break down dead bodies, faeces and excretory wastes
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Decomposers VS Scavengers
1.bacteria and fungi animals e.g. birds and insect 2.saprophytic nutrition ______nutrition 3.no ingestion involved Ingestion of dead The End bodies involved 4. ______digestion Internal digestion
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