B17 - Organising an ecosystem

• Producer


  Photosynthetic organisms that produce biomass for life on Earth
• Producers are at the beginning of all food chains because they produce glucose by photosynthesis
• Food chains


  • Simple models of feeding relationships in a community
  • Most organisms eat a variety of food, not just a single species
• As prey animal numbers go up

  There is plenty of food available for the predators, so predators can reproduce successfully and predator numbers increase
• The high number of predators eat a larger proportion of the prey animals


  Prey numbers fall
• With fewer prey animals

  There is less food for the predators, so they are less successful and predator numbers fall
• With the reduction in predators, and the good food supply that results from fewer animals


  Prey numbers go up again and the cycle repeats itself
• Decomposers are a group of microorganisms that include bacteria and fungi
• Decay process


  1. Detritus feeders start the process

  2. Bacteria and fungi digest everything - dead animals, plants, and detritus feeders plus their waste

  3. They use some of the nutrients to grow and reproduce and release carbon dioxide, water, and mineral ions as waste products
• Decomposers return mineral ions, including nitrates, to the soil
• Decay returns carbon to the atmosphere as carbon dioxide that can be used by producers in photosynthesis
• Water cycle


  1. Evaporation

  2. Condensation

  3. Precipitation

  4. Transpiration

  5. Respiration
• Condensation


  As moist air rises it cools. Water vapour condenses back into liquid water droplets producing clouds
• Evaporation


  The Sun heats the Earth's surface and water is turned from a liquid into water vapour, forming warm moist air
• Transpiration and respiration


  Loss of water vapour from plants and animals directly to the atmosphere
• Precipitation


  As water droplets in clouds get heavier they fall as rain, snow, or hail
• Materials in an ecosystem are recycled to provide the building blocks for future organisms
• Decay of dead animals and plants by microorganisms returns carbon to the atmosphere as carbon dioxide and mineral ions to the soil
• Carbon dioxide in the atmosphere is used by plants in photosynthesis
• The water cycle provides fresh water for plants and animals on land before draining into the seas
• Water is continuously evaporated, condensed, and precipitated
• About 166 gigatonnes of carbon are cycled through the living world every year
• The amount of carbon on the Earth is fixed
• Some carbon is 'locked up' in fossil fuels such as coal, oil, and gas
• Huge amounts of carbon are combined with other elements in carbonate rocks such as limestone and chalk
• There is a pool of carbon in the form of carbon dioxide in the air
• Carbon cycle


  The constant cycling of carbon between living things and the environment
• Main processes in the carbon cycle

  • Photosynthesis
  • Respiration
  • Combustion
• The carbon cycle is important for life on Earth because it returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis, and the decay of dead plants and animals by microorganisms returns carbon to the atmosphere as carbon dioxide
• Sources of carbon dioxide for photosynthesis in plants

  • Carbon dioxide in the air
  • Carbon dioxide dissolved in water, particularly oceans
  • Burning (combustion)
• Photosynthesis


  1. Green plants and algae remove carbon dioxide from the atmosphere

  2. Use the carbon from carbon dioxide to make carbohydrates, proteins, and fats

  3. Carbon is passed on through food chains to animals
• Respiration


  1. Living organisms use oxygen to break down glucose, providing energy

  2. Carbon dioxide and water are produced as waste products

  3. Carbon dioxide is returned to the atmosphere
• Combustion


  Burning wood or fossil fuels releases carbon dioxide into the atmosphere
• For millions of years, the carbon cycle has regulated itself, but as we burn more fossil fuels we are pouring increasing amounts of carbon dioxide into the atmosphere, leading to global warming
• Decomposition


  The process of breaking down waste products, dead animals and plants
• Factors affecting rate of decay

  • Temperature
  • Moisture
  • Oxygen availability
• Decomposers recycle all the molecules of life, with carbon going into the atmosphere as carbon dioxide and mineral ions going into the soil to be used again by growing plants
• Compost


  A brown, crumbly substance made by the breakdown of waste kitchen and garden plant material by decomposers, used as a natural fertiliser
• Making compost


  1. Decomposers break down waste material

  2. Compost is made with or without oxygen, but aerobic respiration speeds up the process

  3. Warmer temperatures and moist conditions also speed up the process
• Biogas generators


  Vessels where plant and/or animal waste is decomposed anaerobically to produce methane gas, which can be used as fuel