Topic 4

• Individual


  Part of a species, lives in its habitat within a population
• Population


  Many different populations interact in the same habitat, creating a community
• Ecosystem


  Interaction of a community with non-living (abiotic) parts of the environment
• Investigating population size using quadrats

  1. Use quadrats to sample a transect area

  2. Count the number of organisms in each quadrat

  3. Estimate the total population size across the whole area
• Quadrats


  • Used to study ecology, make it easier to estimate distribution and abundance of organisms within a large area by looking at a few smaller representative samples
• Transect


  A defined area where the samples will be taken, used to estimate the number of the organism across the whole area
• Percentage cover


  An alternative to counting organisms, but is subjective and less accurate
• Biodiversity


  A measure of the range of species living within an ecosystem
• Investigating biodiversity using quadrats

  1. Use the same quadrat method but count the populations of different species instead of a single organism

  2. Improve reliability by placing quadrats randomly, using the same size, and increasing the number of samples
• Abiotic (non-living) factors


  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
• Biotic (living) factors


  • Food availability
  • New predators
  • New pathogens
  • Competition
• Trophic levels


  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
  • Decomposers
• Food chain


  Shows the feeding relationships between organisms, organised by trophic levels

  
• Food web


  A collection of different food chains to show how all the organisms in the habitat interact, showing interdependence

  
• Pyramid of numbers


  Shows the population of each organism at each trophic level of food chain
• Pyramid of biomass


  Shows the relative dry mass of material at each trophic level
• Producers (e.g plants and algae) transfer about 1% of the incident energy from light for photosynthesis
• Only approximately 10% of the biomass of each trophic level is transferred to the next
• Carbon cycle


  1. Respiration

  2. Photosynthesis

  3. Decomposition

  4. Combustion

  
• Nitrogen cycle


  1. Nitrogen-fixing bacteria

  2. Lightning

  3. Decomposers

  4. Nitrifying-bacteria

  5. Denitrifying bacteria

  
• Air pollutants


  • Sulfur dioxide
  • Carbon monoxide
• Greenhouse gases


  • Water vapour
  • Carbon dioxide
  • Nitrous oxide
  • Methane
  • CFC
• Effects of global warming

  • Climate change
  • Water levels rise
  • Loss of habitats
• Pollution of water by sewage

  1. Decomposers respire aerobically

  2. Algae bloom

  3. Oxygen depletion
• Eutrophication


  When fertilisers are washed off from the land into nearby rivers and lakes, encouraging rapid growth of algae
• Effects of deforestation


  • Leaching
  • Soil erosion
  • Disturbance to cycles
  • Imbalance in oxygen and carbon dioxide