Ecology

• 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

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


  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
• Biotic 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
• Pollution of water by sewage


  • Decomposers and algae thrive
  • Decomposers respire aerobically, using oxygen
  • Algae bloom blocks light, causing aquatic plants to die
  • Oxygen depletion leads to other aquatic organisms dying
• 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