Energy Flow & Nutrient Cycles.

Energy Transfer and Energy Loss.

• Learning objectives;
• Know that photosynthesis is the main route by which energy enters an ecosystem.
• Understand how energy is transferred through the trophic levels in food chains and food webs and is dissipated.
• Know that net productivity is defined by the expression.Net productivity = Gross Productivity - Respiratory Loss.
• Be able to quantify the efficiency of energy transfer between trophic levels.
• Understand pyramids of numbers, biomass and energy and their relationship to their corresponding food chains and webs.
• Specification Reference 3.4.5

Farming Practices and Productivity.

• Learning Objectives;
• Be able to compare natural ecosystems to those based on modern intensive farming in terms of energy input and productivity.
• Know the ways in which productivity is affected by farming practices that increase the efficiency of energy conversion.These include; Intensive rearing of domestic livestock, the use of chemical pesticides, biological agents and integrated systems in controlling pests on agricultural crops, the use of natural and artificial fertilisers.
• Be able to apply your understanding of biological principles to present scientific arguments that explain how these and other farming practices affect productivity.
• Be able to evaluate economic and environmental issues involved with farming practices that increase productivity.
• Consider ethical issues arising from enhancement of productivity.
• Specification reference 3.4.5

The Carbon Cycle and Global Warming.

• Learning objectives;
• Understand the role of microorganisms in the carbon cycle in sufficient detail to illustrate the process of saprophytic nutrition. (The names of individual species are not required.)
• Understand the importance of respiration, photosynthesis and human activity in giving rise to short-term fluctuation and long-term change in global carbon dioxide concentration.
• Understand the roles of carbon dioxide and methane in enhancing the greenhouse effect and bringing about global warming.
• Specification reference 3.4.6

The Nitrogen Cycle.

• Learning objectives;
• Understand the role of microorganisms in the nitrogen cycle in sufficient detail to illustrate the processes of nitrogen fixation, ammonification, nitrification, and denitrification. (The names of individual species are not required.)
• Know the environmental issues arising from the use of fertilisers.
• Understand the processes of leaching and eutrophication.
• Be able to analyse, interpret and evaluate data relating to eutrophication.
• Specification Reference 3.4.6

Energy Transfer and Energy Loss.

• Ecosystems & Energy.

Slide 6

Nitrogen Fertilisers.

• Parts of the nitrogen cycle can be carried out artificially, and on an industrial scale. The Haber process produces ammonia from atmospheric nitrogen -used to make things like fertilisers.
• Nitrogen fertilisers are sprayed onto fields of crops by farmers, so that the crops have enough nitrogen for maximum growth.
• Nitrates leached from fertilised fields stimulate the growth of algae, in ponds and lakes.
• Large amounts of algae block light from reaching the plants below.
• Eventually the plants die because they're unable to photosynthesise enough.
• Bacteria feed on the dead plant matter. The increased numbers of bacteria reduce the oxygen concentration in the water by carrying out aerobic respiration.
• Fish and other aquatic organisms die because there isn't enough dissolved oxygen.

Intensive Farming and Productivity.

• A natural ecosystem is an ecosystem that hasn't been changed by human activity.
• The energy input of a natural ecosystem is the amount of sunlight captured by the producers in the ecosystem.
• Intensive farming involves changing an ecosystem by controlling the biotic and abiotic conditions e.g. the presence of pests or the amount of nutrients available, to make it more favourable for crops or livestock, this means intensively farmed crops or livestock can have greater net productivity (a greater amount of biomass), than organisms is natural ecosystems.

Rearing livestock intensively.

Killing Pest Species

Biological Agents

Slide 12

The Effects of Global Warming.

• Learning Objectives;
• Be able to analyse, interpret and evaluate data relating to evidence of global warming and its effects on;
• the yield of crop plants,
• the life-cycles and numbers of insect pests,
• the distribution and numbers of wild animals and plants.