Transfers of energy and matter

• Ecosystems


  Open systems in which both energy and matter can enter and exit. This Systems only allow the exchange of energy.
• Closed Systems


  Systems where only energy is able to pass in and out
• Sunlight


  The principal source of energy that sustains most ecosystems
• Exceptions to Sunlight as the Principal Energy Source


  • Ecosystems in caves
  • Below the levels of light penetration in oceans
• Flow of Chemical Energy Through Food Chains

  Chemical energy passes to a consumer as it feeds on an organism that is the previous stage in a food chain
• Construction of Food Chains and Food Webs

  Arrows indicate the direction of transfer of energy and biomass
• Supply of Energy to Decomposers

  Carbon compounds in organic matter come from dead organisms (faeces, dead parts of organisms, dead whole organisms)
• Autotrophs


  Organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances
• Energy Source in Photoautotrophs and Chemoautotrophs

  Light and oxidation reactions, respectively
• Heterotrophs


  Organisms that use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require
• Cell Respiration


  Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds
• Trophic Levels


  • Producer
  • Primary consumer
  • Secondary consumer
  • Tertiary consumer
• Decomposers and Detritus Feeders


  Not usually considered to be part of food chains
• Primary Production


  Accumulation of carbon compounds in biomass by autotrophs
• Secondary Production


  Accumulation of carbon compounds in biomass by heterotrophs
• Carbon Cycle Diagrams


  Illustrate how carbon is recycled in ecosystems by photosynthesis, feeding, and respiration
• Combustion


  Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil, and natural gas
• Open Systems


  Ecosystems are open systems where energy and matter can be exchanged
• Sunlight in Ecosystems


  • Sunlight is the initial source of energy that sustains most ecosystems, as it is needed to produce glucose in photosynthesis.
  • Plants, eukaryotic algae, and cyanobacteria carry out photosynthesis and are referred to as producers or autotrophs.
  • Heterotrophs use the sunlight indirectly and are also dependent on it
• Ecosystems With Limited Sunlight


  
  

  • Life is usually adapted to the decreased amount of energy available.
  • In marine and freshwater ecosystems, light must pass through water to reach producers, and transmission is not 100%.
  • In deep-sea ecosystems, the source of energy often originates from bacteria which can use sulfides as a source of energy.
• Flow of Energy


  Energy enters as light, flows as nutrients through the food chains, and usually leaves as heat
• Recycled Nutrients


  • Carbon
  • Nitrogen
  • Phosphorus
• Decomposers


  1. Supplied with energy from carbon compounds in dead organic matter such as faeces, shed exoskeletons, and dead plant material

  2. Secrete digestive enzymes into dead organic matter and digest it externally by absorbing the products of digestion
• Saprotrophs


  Break down complex insoluble carbon compounds into soluble ones, recycling dead matter which would otherwise build up
• Organisms


  • Autotrophs
  • Heterotrophs
  • Photoautotrophs
  • Chemoautotrophs
  • Consumers
  • Saprotrophs
• Photoautotrophs


  Use sunlight as an energy source. A small amount of solar radiation that reaches the Earth is absorbed by chloroplasts
• Chemoautotrophs


  Use sulfur, hydrogen sulfides, iron sulfides, hydrogen, or ammonia as sources of energy that can be oxidized to release energy for synthesizing carbon compounds
• Iron Oxidizing Bacteria


  Use Fe2+ ions and oxidize them to Fe3+ ions. The electrons from this reaction are used to drive energy production (ATP) processes in the cell membrane
• Trophic Levels


  Offer a way of classifying organisms by their feeding relationships within the same ecosystem. Energy transformations in living organisms are never 100% efficient, commonly being 10-20%.
• Energy Loss Reasons


  • Not ingested (eaten)
  • Not digested or assimilated
  • Excreted
  • Lost as heat from respiration
• Heat Energy


  • Lost to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration
  • Heat energy is unusable to organisms and is lost from ecosystems
  • Heat resulting from cell respiration makes living things warmer, passing from hotter to cooler bodies and eventually lost to the abiotic environment
• Energy Forms


  Chemical energy (ATP) produced by an organism through cellular respiration can be converted into electrical energy during nerve impulse transmission, light energy in bioluminescence, or kinetic energy during muscle contractions
• Elements required by living organisms

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
  • Magnesium
  • Calcium
  • Manganese
  • Copper
  • Sodium
  • Potassium
• Nitrogen Cycle


  1. Nitrogen from the air or in organic matter is converted to ammonia and ammonium, then to nitrates, which can be assimilated by plants

  2. Decomposers break down the body parts of dead organisms, converting the nutrients into a more usable form
• Energy Transfers


  • Not 100% efficient, so heat is produced both when ATP is produced in cell respiration and when it is used in cells.
• Food Chains and Biomass

  • At each successive stage in food chains there are fewer organisms or smaller organisms, so there is less biomass, but the energy content per unit mass is not reduced.
• Ecosystems as Carbon Sinks and Sources

  • If photosynthesis exceeds respiration, there is a net uptake of carbon dioxide.
  • If respiration exceeds photosynthesis, there is a net release of carbon dioxide.
• Recycling of Chemical Elements


  • All chemical elements required by living organisms are recycled in ecosystems.
• Aerobic Respiration and Photosynthesis

  • Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration.
• Energy Flow and Pyramids

  • Energy flow can be represented using pyramids of energy.
  • Construction of energy pyramids involves calculating the percentage energy transfer from producers to primary consumers, drawing the pyramid to scale, and labeling each trophic level.