Biology

• Ammonium ions


  Converted to nitrogen in the process of denitrification, by denitrifying bacteria
• Population


  A group of organisms of one species, living in the same area, at the same time
• Community


  All of the populations of different species in an ecosystem
• Ecosystem


  A unit containing the community of organisms and their environment, interacting together
• Factors affecting the rate of population growth for a population of an organism

  • Food supply
  • Competition
  • Predation
  • Disease
• How humans have increased food production

  • Agricultural machinery to use larger areas of land and improve efficiency
  • Chemical fertilisers to improve yields
  • Insecticides to improve quality and yield
  • Herbicides to reduce competition with weeds
  • Selective breeding to improve production by crop plants and livestock
• Disadvantages of monoculture


  • Loss of biodiversity
  • Outbreaks/ spreading of diseases/ pests/ plagues
  • Endangered/ extinction of species
  • Disruption of food chain
  • Loss of habitats/ habitat destruction
  • Deforestation
  • Disrupted soil fertility/ infertility of soil
  • Desertification
  • Soil erosion (by water/ wind)
  • Increased pollution
  • Competition for resources
  • Flooding
  • Disrupted nutrient cycling
• Advantages of monoculture

  • Higher revenue
  • Easier to manage
  • Yields maximization
  • Specialised production
  • Increased productivity and efficiency
• Disadvantages of intensive livestock production

  • Loss of biodiversity
  • Deforestation / habitat loss
  • Use of pesticides
  • Release of, (named) greenhouse gases / carbon emissions
  • Named consequence ; e.g. climate change / global warming
  • Effect of waste (faeces and urine) on, waterways / crops
  • Disease spreading to, wild populations / humans
  • Use of antibiotics and (spread of) antibiotic resistance
  • Providing food for livestock requires monocultures
  • Idea that livestock production is an inefficient use of, crop plants / energy
• Advantages of intensive livestock production

  • Help to provide more food for people
  • Sometime provide food more cheaply than extensive systems
  • Fewer people go hungry
  • Take up less land
  • More land could be left in its natural state, providing habitats for other species
• Biodiversity

  The number of different species that live in an area
• Reasons for habitat destruction

  • Increased area for housing, crop plant production and livestock production
  • Extraction of natural resources
  • Freshwater and marine pollution
• Through altering food webs and food chains, humans can have a negative impact on habitats
• Effects of deforestation


  • Habitat destruction
  • Reducing biodiversity
  • Extinction
  • Loss of soil
  • Flooding
  • Increase of carbon dioxide in the atmosphere
• Effect of pollution and excess fertilisers in aquatic ecosystems

  • Lake/ river pH decrease
  • Aluminium ions become mobile
  • Nutrients leached
  • Shell damage
  • Fish/ frog fail to reproduce
  • Aquatic plants die
  • Disruption of food chain
  • Loss of biodiversity
  • Low pH toxic to aquatic animals
  • Fish produce mucus which blocks gills
• Effect of plastic on aquatic ecosystem

  • Plastic remains /persists / lasts a long time/ not decomposed
  • Swallowed/ ingested/eaten/ cannot be digested/ blocks gut
  • Caught, around/ strangle/trapped/ entangled/ smother/ suffocate / injure/ cut / trap/ stuck in, organism AW
  • Plastic blocks light for, photosynthesis
  • May, contain/release, (oil-soluble) toxins / poisons / harmful chemicals
  • Blocks the flow of water in streams or rivers
  • So less aeration of water/reduces concentration of (dissolved) oxygen
  • Destruction of, habitat/ ecosystem/ food chain
  • Idea of bioaccumulation/ biomagnification
  • Trapped / stationary water acts as a breeding site for mosquitoes
  • AVP ; e.g. visual pollution /releases hormone-like chemicals / less oxygen from photosynthesis
• Effect of plastic on terrestrial ecosystem

  • Chokes / strangles / traps / blocks digestive systems / AW (of animals) ingested
  • Reference to, chemical exposure / fumes / toxins
  • (Plastic) accumulates in an organism / is passed down a food chain
  • (Described) habitat destruction
  • (Plastic) block roots / prevents root growth
  • Remain in the ecosystem (for a very long time)
• Methane and carbon dioxide are green house gases. They trap infrared radiation emitted from the sun towards the earth. This keeps the planet warm enough to support life. If level of these green house gases rise, more infrared radiation is trapped, this increase the average temperature of earth. Resulting in enhanced green house effect, leading to climate change
• Eutrophication of water


  1. Increased availability of nitrate and other ions

  2. Increased growth of producers

  3. Increased decomposition after death of producers

  4. Increased aerobic respiration by decomposers

  5. Reduction in dissolved oxygen

  6. Death of organisms requiring dissolved oxygen in water
• Sustainable resource


  One which is produced as rapidly as it is removed from the environment so that it does not run out
• Some resources can be conserved and managed sustainably, e.g. forests and fish stocks