Unit 4

• Population: a group of organisms of the same species who live in the same area at the same time
• Habitat: The environment in which a species normally lives or the location of a living organism
• community: a group of populations living and interacting with each other in an area
• ecosystem is a unit containing all of the organisms and their environment, interacting together, in a given area
• the square used for the unit 4 practicals is called a quadrat
• Samples have to be representative (at least 5% of the habitat)
• Biodiversity is the variety of living species living within a particular ecosystem or habitat
• A food chain is a chart showing FLOW OF ENERGY from one organism to the next
• Food web => interconnected food chains, through part of an ecosystem
• decomposers get their energy from dead or waste organic matter
• Energy is lost between trophic levels due to respiration, faeces, heat loss, movement, indigestible material.
• Pyramid of numbers: exceptions include trees
• Pyramid of biomass is generally always in descending size order upwards.
• Biomass is a measure of the total mass of living material in each trophic level.
• Pyramid of energy => roughly 10% of energy is present in the next trophic level
• Fill in the blanks of this pyramid of energy

  A) Tertiary

  B) 1

  C) Secondary

  D) Primary

  E) Producers

  F) 10

  G) 100

  
• Fill in the blanks of this diagram of the carbon cycle.

  A) air

  B) photosynthesis

  C) plants

  D) decay

  E) decomposers

  F) urine

  G) microorganisms

  H) respiration

  I) feeding

  J) combustion

  K) fossil fuels

  L) fossilisation

  
• Nitrogen is required for : amino acids, proteins, DNA, and chlorophyll
• Nitrogen must be in a fixed form (compounds of amino acids and proteins, or ions [ie. nitrate and ammonia])
• Fill in the blanks of this diagram of the nitrogen cycle:

  A) fixation

  B) bacteria

  C) root nodules

  D) plants

  E) animals

  F) denitrification

  G) decomposition

  H) nitrate

  I) ammonia

  J) plants

  K) Nitrogen

  
• Plants mostly obtain nitrogen in the form of nitrate ions (NO3)
• Nitrate ions are used to make amino acids in leaves, which are used to form proteins such as enzymes.
• Animals eat plants, and eventually after the animals and plants die nitrogen is recycled from their dead matter by decomposers/microorganisms.
• Ammonification: Decomposers break down remains and animal wastes and release ammonium ions (NH4) into the soil. This also occurs with urea in urine.
• Nitrifying bacteria are found in the soil and they change ammonium ions into nitrate ions. They gain their source of energy from this oxidation reaction.
• Nitrogen fixing bacteria are found in the soil. They convert nitrogen gas from the air into compounds of nitrogen they use. When these bacteria die and decompose the fixed nitrogen is available to the plant.
• Nitrogen fixing bacteria in root nodules of plants change nitrogen gas into ammonia, and these legume plants can use that ammonia to make amino acids. In return the legume plants provide 2 things:

  1. Suitable habitat for bacteria
  2. Produce sugars for bacteria to use for respiration and energy
• In water-logged soil you can find denitrifying bacteria, which change nitrate ions into nitrogen gas. Their role in the nitrogen cycle is to balance the uptake of nitrogen gas by nitrogen-fixing bacteria.
• Lighting causes nitrogen oxides to be formed due to high temperatures, and these get washed into the soil where they form nitrate ions.
• Impacts of deforestation:

  1. extinction -> habitat and food source loss
  2. loss of soil -> erosion, land slides and loss of nutrients for growing crops
  3. leaching -> nutrients lost from soil, deposited into lakes and rivers
  4. evapotranspiration -> rainwater not absorbed, released back into atmosphere, runs off quicker causing flooding
  5. Less CO2 absorbed -> global warming
• Greenhouse gases:

  • Water vapour
  • Carbon Dioxide
  • Nitrous Oxide
  • Methane
  • CFCs
• Acid rain is caused by the burning of fossil fuels leading to high concentrations of : Sulphur dioxide, Carbon monoxide, Nitrogen oxides -> these gases dissolve in rain water and form acid rain.
• Acid rain can have a pH as low as pH 4
• How can you reduce the impact of acid rain?

  Reduce emissions, scrub power stations by passing gases through lime, using catalytic converters that remove nitrogen oxides released when petrol is burnt
• Sewage pollution is the release of untreated raw organic matter into rivers and lakes.
• Sewage pollution leads to an explosion in bacteria population as they break down the sewage, these bacteria deplete the oxygen concentration for aerobic respiration which kills other life in the water. This also causes eutrophication.