Energy Flow

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  • Energy Flow
    • Food chains.
      • Food chains show the feeding relationships in a habitat. Pyramids of biomass are charts that show the mass of living organisms at each step in a food chain.
      • Energy is lost moving up in a food chain and this limits the length of the chain. A food chain shows what eats what in a particular habitat.
        • For example grass seed is eaten by a vole which is eaten by a barn owl. The arrows between each item in a chain go from food to feeder.
      • Radiation from the sun is the ultimate source of energy for most communities of living things.
      • Green plants and algae convert some of the suns light energy into chemical energy. This happens during photosynthesis and the chemical energy is stored in the substances that make up the cells of the plants or algae.
      • Other organisms in a food chain are consumers because they gain their energy from consuming other organisms.
    • Food chain terms.
      • Producers - Green plants and algae, they make food by photosynthesis
      • Primary consumers -Usually eat plant material, they are herbivores. For example rabbits, cows, sheep.
      • Secondary consumers - Usually eat animal material, they are carnivores. For example cats, dogs and lions.
      • Predators - Kill for food. They are either secondary or tertiary consumers.
      • Prey - The animals that predators feed on.
      • Scavengers - Feed on dead animals. For example, crows, vultures and hyenas.
      • Decomposers - Feed on dead or decaying organisms and the undigested part of plant and animal matter in faeces.
    • Energy Transfer.
      • Energy is transferred along food chains from one stage to the next. But not all the energy from one stage can be absorbed by the organism in the next.
      • The amount of available energy decreases from one stage to the next. Some of the available energy goes into growth and producing offspring.
        • This energy becomes available to the next stage, but most of the available energy is used up in other ways.
          • For example: Energy released by respiration is used for movement and other life processes. It is eventually lost as heat to the surroundings.Energy is lost in waste materials such as faeces.
            • All the energy used in these ways returns to the environment and is not available in the next stage. Most food chains are pretty short. There are rarely more than four stages because so much energy is lost at each one.
    • Pyramids of biomass.
      • Biomass means the dry mass of something at a stage in the food chain. The biomass goes down from one stage to the next, just like the energy.
        • Each stage in a foodchain or a pyramid of biomass is called a trophic level.
        • It can be difficult to make a pyramid of biomass because there may be problems measuring dry biomass and an organism may be belong to more than one trophic level and so is represented by more than one bar.
      • A pyramid of biomass is a chart, drawn to scale, showing the biomass at each stage in the food chain. The bars become narrower as you reach the top.
      • You do not need to draw the organisms but you much draw the pyramid of biomass to scale. Each bar should be labelled with the name of the organism.


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