Topic 2 - transfer of energy by all living things

• Radiation from the sun is the source of energy for most ecosystems and communities of living organisms.
• The food animals eat contains stored chemical energy. When eaten, this chemical energy is released by the process of respiration.
• Living things get their food in one of two ways: they make it by photosynthesis or they obtain it by feeding from living thing.
• Green plants and algae are able to make their own food by photosynthesis.
• Plants are given the name producers because they make their own food.
• Green plants and algae only capture a small % of the solar energy which reaches them.
• Animals cannot make their own food, they obtain their food by eating other living organisms. They are given the name consumers
• Food chains: the direction of the arrows is the direction of energy flow/transfer from one organism to another.
• Food chain example: grass, rabbit, fox. Grass = producer, Rabbit = primary consumer, fox = secondary consumer.
• Food chains: all food chains start with photosynthetic organisms like green plants and algae (the producers).
• Decomposers such as bacteria and fungi break down dead organic matter and release nutrients back into the soil.
• During decomposition microbes respire and release carbon dioxide and water. They require adequate temperature and oxygen.
• When conditions prevent decay occurring energy remains locked in carbon compounds such as fossil fuels (coal, oil and gas).
• As energy is lost at each tropic (feeding) level its more energy efficient to eat the organisms nearer the start of the food chain.
• Trophic (level) efficiency = energy in later stage/energy in earlier stage x 100%.
• Energy is used in repair and in the maintenance and growth of cells. Energy is lost in waste materials and respiration. Efficiency of each stage can be calculated by Pyramids of number/biomass.
• Pyramids of number - show how many organisms are in each trophic level.
• Pyramids of biomass - show the dry weight of organisms at each trophic level.
• A growing population means that more space is needed for housing, industry and agriculture. These will have an environmental impact polluting and endangering species.
• Eutrophication: caused by fertilisers and untreated sewage.
• Eutrophication: If either sewage or fertilisers gets washed from the crops where farmers have grown them into rivers, it can cause the water to become too rich in nutrients.
• Eutrophication: fertilisers/untreated sewage can we washed into rivers, lakes and ponds.
• Eutrophication: The nitrates in the sewage and fertilisers increase the growth of algae (called an algal bloom) and water plants.
• Eutrophication: when algae and water plants die, theyre broken down by microbes, the increase in food for the microbes allows them to increase in number.
• Eutrophication: Respiration of the now huge numbers of microbes use up oxygen in the water and fish and other aquatic organisms suffocate and die.