energy transfer in ecosystems

• the two main types of decomposers are bacteria and fungi
• how do microorganisms help to recycle chemicals?

  • the decomposers respire which releases carbon dioxide
  • the plants reabsorb the carbon dioxide for photosynthesis so that they can create glucose
  • decomposers also secrete enzymes which digest organic matter
  • and increase the amount of ions in the soil
  • the plants reabsorb the ions through active transport in the roots
  • they then use the nitrate ions for growth
• biomass is the physical mass of living things
• dry biomass is used because it's much more accurate
• biomass is recorded using mass per area
• 100% of biomass may not get passed on at each stage of the food chain because:

  • it's lost in respiration
  • egestion (faeces, undigested food)
  • excretion/urea/urine
  • not all eaten
• plants get energy from the light they absorb through their chloroplasts
• how energy is lost: heat:

  heat is lost as a waste energy transfer from respiration e.g movement and keeping warm
• how energy is lost: not all eaten:

  e.g bones, cartilage, leaf litter not eaten so biomass isn't passed on
• how energy is lost: faeces and urine

  undigested food = fibre = biomass lost

  excess proteins turn into urea = biomass lost
• if animals exercise more, they respire more so they lose more energy as heat
• animals need to eat more in the winter because more heat is lost in maintaining warm body temps as surroundings are colder so there's a steeper heat loss gradient
• snakes only need to eat once a month, which is a small amount compared to other animals because mammals and birds maintain a warm body temperature, so they lose a lot of heat energy to the surroundings, so they need more food for more respiration so they get more heat
• decomposers are in every single food chain/web because all the uneaten remains of food and wastes such as leaf litter, faeces and urine must be decayed into recycled elements such as carbon and nitrogen
• food security is having enough food to feed a population
• factors threatening food security:

  1. increasing birth rate
  2. changing diets in developing countries
  3. new pests and pathogens
  4. environmental change
  5. loss of agricultural inputs
  6. conflicts
• sustainable solutions to food security:

  • maintaining soil quality (so plants grow well every year)
  • look after fish stock in the ocean (so they don't run out)
  • sustainable meat production (use grass as animal feed)
  • urban farming initiatives
  • educating populations about sustainable food
  • reducing food waste
• more efficient ways of producing food:

  • intensive farming of plants (monoculture) and animals
  • organic farming; crop rotation
  • selective breeding
  • GM technology
• intensive farming is trying to produce as much food as possible from the land, plants and animals available - it's about producing more food for less cost
• intensive farming methods are needed to increase the efficiency of food production
• examples of intensive farming methods:

  • limiting the movement of food animals so they don't use their muscles much. this reduces the need for respiration so they have more biomass available from their food for growth
  • controlling the temperature of the surroundings so animals do not have to use as much biomass in respiration for keeping warm or cooling down
  • reduce the number of stages in the food chain
• advantages of intensive farming:

  • the animals are ready to eat in a matter of weeks
  • contented animals gain biomass quicker than stressed ones
  • more food is produced in the same amount of space
  • cheaper food prices
  • more energy efficient
• disadvantages of intensive farming methods:

  • risk of disease spreading quickly because the animals have a limited amount of space
  • they need to be monitored which costs money
  • ethical objections
  • the animals have a bad quality of life
  • reduced biodiversity
  • using antibiotics can lead to antibiotic resistance
• fish stocks are depleting because of overfishing
• laws on fishing:

  • bans on fishing in the breeding season
  • strict quotas imposed on fishermen - they have a strictly enforced limit on the amount and type of fish they're allowed to catch
  • size of the gaps in fishing nets have been increased
• why is it more energy efficient to rear cows indoors?

  they move around less and they don't need to use as much energy to keep warm
• disadvantages of rearing cows indoors:

  higher cost, ethical issues, spread of disease
• fungus Fusarium is used to produced mycoprotein
• the temperature and ph are maintained during the production of mycoprotein for optimum enzyme activity
• the temperature is maintained during the production of mycoprotein by the water jacket
• sterile oxygen is added during the production of mycoprotein so that it doesn't get contaminated with other microbes
• glucose and oxygen are added during the production of mycoprotein for aerobic respiration
• the production of mycoprotein is quicker, suitable for vegetarians, cheaper, more efficient, uses less land, produces less methane
• describe how mycoprotein is produced:

  fungus fusarium is added into the fermenter

  glucose and sterile oxygen are added

  the mixture gets stirred

  mycoprotein is then harvested

  all of this happens in aerobic conditions