GCSE Biology 1.6 Ecosystems, Nutrient Cycles & Human Impact PDF

GCSE Biology 1.6 Ecosystems, nutrient cycles and human impact on the environment knowledge organiser Energy flow Pyramids of biomass show the dry weight of organisms at Bioaccumulation - c...

GCSE Biology 1.6 Ecosystems, nutrient cycles and human impact on the environment knowledge organiser Energy flow Pyramids of biomass show the dry weight of organisms at Bioaccumulation - caused by: each trophic level. Energy from the sun is the source of energy for all life on Pesticides earth. Green plants absorb about 1% of this energy during 0.3gm Robin -2 Heavy metals (industrial waste) photosynthesis. 1.25gm-2 Slugs These substances can be washed into soils and rivers. If Carnivores- eat other animals. Producer- Green Herbivore- eats These represent the secondary they enter the food chain: plant store energy only plants, a and then tertiary (second and third They are persistent: do not break down in animal as glucose. primary (first stage) consumer. stage) consumers. 417gm-2 Grass tissues and so They accumulate along the food chain until they Oak leves Slug Thrush Sparrowhawk Intensive farming reach toxic levels The increasing population means farming has changed to Causing reduced fertility or death in top predators. Arrows in food chain increase the yields of crops and meat produced. Decomposers - break down stored energy in dead organisms and return nutrients to the soil to be taken up by plants. represent the direction the energy flows. Indicator species This is done by: A growing population means that more space is needed As energy is lost at each trophic level it is more energy Using fertilisers and pesticides for: efficient to eat the organisms nearer the start of the food Battery farming Housing chain. Disease control Industry Energy is used at each trophic (feeding) level in the chain The disadvantages of these methods include: Agriculture (only around 10% in passed on) This limits the number of Excess use of antibiotics in farm animals for disease These will have an environmental impact polluting organisms in the chain. control could increase bacterial resistance and still be and endangering species. Government agencies energy in later stage present in meat we eat. have an important role in monitoring, protecting and Trophic efficiency = x 100% Battery methods show poor animal welfare and the improving the environment. duty of care to treat animals humanely. energy in earlier stage Pollution can be measured in a few ways Other disadvantages Measure oxygen levels (less oxygen -more Energy is used in repair and in the maintenance and Eutrophication - Caused by: pollution) growth of cells. Energy is lost in waste materials and Fertilisers Measure pH levels respiration. Efficiency of each stage can be calculated by: Untreated Sewage Lichens are used to indicate Pyramids of number/biomass air pollution (sulphur dioxide in If either of these substances is washed from the crops To build either pyramid start at the bottom with the air). Some species will only grow where farmers have placed them to increase growth of producer and continue up the pyramid following the food in clean air, others can tolerate plants then: chain. higher levels of pollution. Very They can be washed into rivers, lakes, ponds. Pyramids of number - show how many organisms are in high levels of pollution no species each trophic level. The nitrates in the sewage and fertilisers increase the will grow. growth of algae and water plants. When these die they are broken down by microbes, Freshwater invertebrates – Some invertebrates can 2 robins 10 robins the increase in food for the microbes allows them to only live in very clean water; others can tolerate more increase in number. pollution. Collecting samples of water and recording the 200 caterpillars 8000 caterpillars Respiration of the now huge numbers of microbes invertebrates found can indicate the level of pollution. use up the oxygen in the water and fish and other 300 cabbages 1 oak tree aquatic organisms suffocate and die. GCSE Biology 1.6 Ecosystems, nutrient cycles and human impact on the environment knowledge organiser - Separate Science Only Decomposition Waste and dead organisms are broken down into useful substances by the action Carbon dioxide in the atmosphere of decomposers e.g. microbes (bacteria and Nitrogen in the atmosphere fungi). CO2 In a stable community the process which N2 decomposes organic material returning nutrients (nitrates and phosphates) to the soil are balanced by those that remove these substances for use (plants). 2 1 2 During decomposition microbes respire (an enzyme dependent reaction) producing Plants are eaten by animals and carbon dioxide. They therefore require: Plants carry out photosynthesis (1) the carbon then becomes part of Animals eat the plant proteins and use converting carbon dioxide from the Adequate temperature their bodies (carbohydrates, proteins, Plants absorb nitrates from them in their bodies or excrete excess atmosphere into carbohydrates. fats) or is used in respiration (2) which Oxygen the soil to make proteins. in urine. They also carry out respiration (2). releases carbon dioxide. They are also sensitive to: 5 3 4 pH 6 Heavy metals When conditions prevent decay occurring energy remains locked in carbon compounds such as fossil fuels. Coal Decomposers- bacteria and fungi Oil Nitrogen fixing bacteria in the root break down proteins and urea into Gas nodules of leguminous plants and ammonia. Urease enzyme can break some free-living bacteria in soil The cycling of two useful substances in down urea into ammonia and carbon dioxide. Animal death (3) occurs and if the nature are shown here. convert gaseous nitrogen into If conditions do not support decomposition conditions are correct decomposers nitrates that plants can absorb. energy is stored in carbon compounds break down their bodies releasing In poor soil conditions like during fossilization (5). Fossil fuels release carbon dioxide- decomposition (4). waterlogged/unploughed soil (lacking carbon dioxide during combustion (6). Other bacteria convert ammonia oxygen), denitrifying bacteria make soil useless to plants by turning the nitrates back into nitrates that plants can into atmospheric nitrogen. absorb.