Applicable for A-Level, IB, DSE, AP-Level Exams

Biological Molecules    Cell Structure    Cell Transport    Immunology    Exchange    Mass Transport    DNA, Genes & Protein Synthesis    Genetic Diversity    Biodiversity    Photosynthesis    Respiration    Energy & Ecosystems    Stimuli and Response    Nervous Coordination & Muscles    Homeostasis    Inheritance    Populations & Evolution    Ecosystems    Gene Expression    Recombinant DNA Technology   

Energy Transfer in Ecosystems

In land-based and aquatic ecosystems, plants synthesise organic compounds from atmospheric/aquatic CO2 during photosynthesis. Biomass can be measured in terms of mass of carbon or dry mass of tissue per given area. GPP is the chemical energy store in plant biomass whereas NPP is the chemical energy store in plant biomass after respiratory losses to the environent has been taken into account.

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Farming Practices and Production

To improve efficiency of biomass transfer within farming, farmers can simply food webs to reduce energy losses to non-human food chains. In addition, they can reduce respiratory losses within a human food chain by restricting movement in pens for example.

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Nutrient Cycles

Nutrients are recycled through ecoystems as they do not have an extraterrestrial source. Saprobionts help in decomposition via extracellular digestion. Mycoorhizae are associations between certain type of fungi and the roots of majority of plants.

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Nitrogen Cycle

Nitrogen cycle occurs in a couple stages: Nitrogen Fixation, Ammonification, Nitrification and Denitrification.

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Phosphorus Cycle

Within the phosphorus cycle, phosphate ions are released into the soil from rocks by weathering. These phosphate ions, with the assistance of mycoohizae, are assimilated into plant DNA and organic molecules. Phosphate ions are then passed along the food chain and are returned via faeces. Phosphate ions can also be passed into aquatic life and food chains and are mainly passed back into the soil via guano.

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Fertilisers and Eutrophication

Organic fertilisers are from the remains of animals and helps the soil structure. Inroganic fertilisers contain a distinct amount of ions required for the growth of crops. Excessive fertiliser use can cause leaching and eventually fertilisers will be washed to rivers and lakes and cause eutrophication: Growth of algae on the surface of the water blocks sunlight and kills aquatic plants; saptrobiotic bacteria decompose the plants and use up oxygen in aerobic respiration. Oyxgen is used up and fishes die as a result.

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