Ecosystems

• green plants absorb only a small percentage of light energy from the sun because most of the light is either reflected or is the wrong wavelength
• in green plants, the absorbed energy is used for photosynthesis to produce substances that become part of the cells which increase the biomass of the plant
• biomass is the mass of living material in plants and animals
• producer --> primary consumer --> secondary consumer --> tertiary consumer --> quaternary consumer
• energy is lost at each stage of the food chain due to:

  respiration

  growth

  waste

  movement
• animals lose more heat from respiration than plants do because animals move around
• warm blooded animals lose more heat from respiration than cold blooded animals 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 its used to grow crops than animals because less energy is lost when the food chain is shorter
• pyramids of numbers can be misleading because for example one tree can support and feed thousands of animals
• shape of pyramid of biomass can change during the year depending on the time a survey is carried out because in winter months there's less sunlight so plants carry out less photosynthesis and produce less biomass
• decomposers are bacteria and fungi
• factors that affect decomposers:

  • temperature
  • oxygen
  • pH
  • heavy metals
• combustion releases carbon dioxide
• in intensive farming, chemicals are sprayed on the crops which may get into the food chain and enter our bodies due to bioaccumulation
• in intensive farming, pesticides can kill useful insects
• in intensive farming, fertilisers can cause eutrophication
• in intensive farming, higher yield means more food is produced
• in intensive farming, food is cheaper to produce so the farmer makes more money
• in intensive farming, the food is cheaper in shops
• in intensive farming, there's a much higher yield per available space
• carbon enters the food chain via photosynthesis
• in plants, some of carbon taken in then becomes carbohydrates, fats and proteins
• some carbon is converted to carbon dioxide during respiration by plants and animals
• carbon is returned to the environment when living things die or produce waste material
• decomposers such as bacteria or fungi feed on dead organisms and the waste material. This is called decomposition or decay
• combustion of fossil fuels increase carbon dioxide in the environment
• combustion of fossil fuels release sulphur dioxide that leads to acid rain
• living organisms need nitrates to make proteins
• plants and animals cant use nitrogen gas
• nitrogen must be change into nitrates before plants can use it
• nitrogen can make protein and DNA
• nitrogen fixing bacteria converts nitrogen gas into nitrates in soil
• nitrates are needed to build plant and animal proteins
• when waste dead plants and animals are broken down, they release nitrates back into soil
• nitrifying bacteria convert ammonia into nitrates
• other bacteria convert waste/dead animals/plants into ammonia
• denitrifying bacteria converts nitrates into nitrogen
• nitrifying bacteria uses aerobic respiration
• denitrifying bacteria uses anaerobic respiration