organising an ecosystem

• on land, producers are almost always green plants. in the ocean, producers are usually algae or phytoplankton. they are at the beginning of the food chain because they produce glucose from photosynthesis.
• the animals that eat the producers are called primary consumers. these are herbivores e.g. sheep, caterpillars and some birds. in the ocean this could be zooplankton, shrimps, crabs and small fish.
• primary consumers are eaten by the secondary consumers. these are carnivores like lions, eagles and chameleons. in the ocean, this could be larger fish, turtles and seals.
• secondary consumers are eaten by the tertiary consumers. these are large carnivores like polar bears, birds of prey and tigers.
• primary consumers eating plants had positives and negatives. plants don't move around so they are easily accessible but they are made of cellulose which is hard to break down and digest.
• secondary and tertiary consumers have different problems. their food is high in protein and easier to digest, but animals move. before they can eat them, they must catch them.
• consumers that eat other animals are known as predators. consumers that are eaten are known as prey.
• in a stable community, the number of predators and prey rise and fall in linked cycles>
• a stable community is one where all biotic and abiotic factors are in balance.
• decomposers are a group of organisms that break down the waste and the dead animals and plants
• the water cycle

  • energy from the sun causes some water to evapourate
  • as this rises, the water condenses to form clouds
  • the clouds move and eventually precipitation will happen
  • the water could then seep into the soil, flow into rivers or be taken into plants
  • the cycle will then repeat.
• the carbon stores are the air, plants, soil, fossil fuels and animals.
• the carbon cycle

  • photosynthesis happens and plants take in carbon dioxide from the atmosphere and convert into glucose
  • carbon can either be passed back out into air by respiration, or passed onto animals that eat the plants
  • the animals themselves could also respire
  • when the plants and animals die, the organisms can decay and carbon dioxide will be released
  • if they decay in anaerobic conditions, they could become fossil fuels which will be burnt by humans and again be released
• the carbon cycle starts with carbon dioxide in the atmosphere

  it enters the cycle by photosynthesis. it returns back into atmosphere by aerobic respiration.
• carbon is used to plants to make carbohydrates, fats and proteins which make up the cells of plants and algae
• all animals and plants die, we then have carbon in waste products and dead remains. these are then broken down by decomposing microorganisms e.g. bacteria and fungi. when decomposers carry out respiration, the carbon in the dead remains and waste products returns to the atmosphere.
• decomposers are extremely important as they cycle materials through an ecosystem, and return carbon dioxide to atmosphere. they also release mineral ions to soil
• under certain conditions, e.g. lack of oxygen, decomposers cannot function effectively. if this happens then the carbon in the dead remains is slowly converted to fossil fuels.
• when fossil fuels are burnt, the carbon is released back into the atmosphere
• gardeners put dead plant material e.g. grass into a compost heap. over time, bacteria and fungi decompose the plant material and produce compost. gardeners and farmers then use the compost as a natural fertiliser. this is because compost is very rich in minerals that plants need to grow
• one of the conditions for optimum decomposition is warm temperatures. this is because the decomposers use enzymes to breakdown the plant materials, and enzymes work faster in warm conditions. compost heaps tend to be warm anyway because decomposers release energy when they carry out aerobic respiration.
• it is important that compost doesn't get too hot or the enzymes will denature and decomposers can die
• another condition for optimum decomposing is moisture. the amount for water needs to be enough so the area is moist. this is because many of the chemicals in decay require water so its important that compost heaps don't dry out.
• another condition for optimum decomposing is sufficient oxygen. decomposers carry out aerobic respiration and this requires a good supply of oxygen. compost bins may have holes in the wall to allow oxygen to enter and gardeners can mix compost regularly so more oxygen passes to the centre. as wells as breaking up large clumps, this can increase the surface area for decomposers to act on.
• in the absence of oxygen, decomposing microorganisms carry out anaerobic decay. anaerobic decay produces a mixture of gases including methane, we call this biogas.
• biogas can be used small scale in biogas generators to provide fuel for homes
• plant and animal waste can be put into special vessels called biogas generators. waste will produce methane gas. these generators work best in hot climate
• REQUIRED PRACTICAL: investigate the effect of temperature on the rate of decay of fresh milk by measuring the pH change.
• RP: when we leave milk out, it will go sour because bacteria in the milk start decay process. the bacteria use enzymes to make acidic molecule, hence why it tastes sour and acidic.
• RQP P1:

  1. label test tube lipase
  2. use pipette to place 5cm of lipase solution into test tube
  3. get another testube and label milk
  4. add 5 drops of indicator cresol red to test tube
  5. add 5cm of milk and 7cm of sodium carbonate solution to milk test tube
  6. the solution should be purple because sodium carbonate is alkaline and cresol red goes purple in alkaline conditions
  7. place thermometer in both test tubes
• RQP P2:

  1. place both test tubes in beaker of water at chosen temperature (20)
  2. then wait until temp of solutions is the same as beaker
  3. use pipette to transfer 1cm of lipase solution to test tube containing milk and stir.
  4. start timer
  5. the enzyme lipase will break down fat molecules, releasing fatty acids, causing milk solution to be acidic
  6. in acidic conditions, cresol red changes to yellow, we will then stop timing and repat in new temperatures.
• RQP;

  independant variable - temperature

  dependant variable - time taken for milk solution to turn yellow

  control variable - volumes of different solutions

  we must use a clean test tube each experiment, because any traces of lipase will trigger reaction

  share data with other groups and calculate mean