Ecosystems

• Light energy from the sun


  Source of all energy for all living things on the planet
• Green plants


  • Absorb only a small percentage (about 1%) of the light energy using the chlorophyll in their chloroplasts
  • The rest of the light is either reflected or is at the wrong wavelength
• Absorbed energy


  Used for photosynthesis to produce substances that become part of the cells, increasing the biomass of the plant
• Biomass


  The mass of living material in plants and animals
• Light energy from the sun


  Source of all energy for all living things on the planet
• Green plants


  • Absorb only a small percentage (about 1%) of the light energy using the chlorophyll in their chloroplasts
  • The rest of the light is either reflected or is at the wrong wavelength
• Absorbed energy


  Used for photosynthesis to produce substances that become part of the cells, increasing the biomass of the plant
• Biomass


  The mass of living material in plants and animals
• Organisms that can be described using more than one label

  • Herbivore
  • First stage (primary) consumer
• Types of consumers


  • Producer
  • Herbivore
  • Carnivore
  • Omnivore
• Producer


  Makes its own food by photosynthesis
• Consumer


  An organism that eats other organisms
• First stage (primary) consumer

  The first organism that is 'eating' in a food chain
• Second stage (secondary) consumer


  The second organism that is 'eating' in a food chain
• Third stage (tertiary) consumer

  The third organism that is 'eating' in a food chain
• Herbivore


  An organism that only eats plants
• Carnivore


  An organism that only eats animals
• Omnivore


  An organism that eats both animals and plants
• The arrows in a food chain show energy being passed from one living thing to the next (sometimes described as a flow of energy)
• Food webs are made from a number of different food chains linked together
• There is energy lost at each step of a food chain, so there's less available for the next animal. This is why the numbers of organisms in a food chain is limited.
• The more energy lost every step, the shorter the food chain
• Waste materials from plants and animals

  • Dead plants
  • Dead animals
  • Excretion (Urine)
  • Egestion (faeces)
• Animals


  • Lose more heat from respiration than plants because their metabolism is higher
  • Lose more heat from respiration than plants because they move around
  • Warm-blooded animals (mammals and birds) lose more heat from respiration than cold-blooded animals (all the others) because they need to keep their body temperature constant
  • Land animals lose more energy from respiration than animals in water, because they have to support their bodies
• More food can be produced from an area of land if it is used for growing crops rather than grazing animals, because the food chain is shorter
• Pyramid of numbers


  Shows the number of organisms in a given area or volume for every feeding level
• Rules for pyramids of number


  • The producer is always at the bottom

  2. The size of every block (area or volume) shows the number of plants or animals in the food chain
• Pyramids of numbers can be misleading as the shape depends on the ecosystem
• Pyramid of biomass


  Shows the dry mass of organisms in a given area or volume for every feeding level
• Rules for pyramids of biomass


  • The producer is always at the bottom

  2. The size of every block (area or volume) shows the dry mass of the plants or animals in the food chain
• The shape of a pyramid of biomass can change during the year, depending on the time a survey is carried out
• Building food pyramids


  Organisms are represented as small squares on graph paper

  2. Drawing a line around all the small squares will give a box that represents the numbers or biomass of an organism

  3. Keep the height of each block the same

  4. The length of the block should be drawn to scale
• Trophic efficiency


  The efficiency of energy transfer at any stage, calculated as: energy in later stage / energy in earlier stage x 100%
• Decomposers


  Bacteria and fungi that feed on dead organic material
• Micro-organisms, such as bacteria and fungi, digest material from their environment for growth and other life processes
• Materials are returned to the environment either in waste products or when living things die and decay
• Minerals such as nitrates and phosphates are released to the soil, and are then used by plants for growth
• Micro-organisms release carbon dioxide into the air as they respire
• When decay is prevented, fossil fuels such as coal, oil and gas are formed and these store energy in carbon compounds
• Factors that affect the activity of decomposers

  • Temperature
  • Oxygen
  • pH
  • Heavy metals