Ecology topic

• 9.1 Levels of Organisation

  Individual - part of a species, but lives in its habitat within a population.

  Different populations interact in the same habitat, creating a community. Populations are often dependent on each other

  Ecosystem - interaction of a community with non-living (abiotic) parts of the environment. Organisms are adapted to live in the conditions of their environment.
• 9.1 Levels of Organisation

  Organisms which need the same resources compete for it:

  • There can be competition within a species of between different species
• 9.2 Abiotic and Biotic Factors Affecting Communities

  Abiotic = non-living

  Abiotic factors:

  1. Light intensity
  2. Temperature
  3. Moisture levels
  4. Soil pH and mineral content
  5. Wind intensity and direction
  6. Carbon dioxide Levels
  7. Oxygen levels for aquatic animals
• 9.2 Abiotic and Biotic Factors Affecting Communities

  Biotic = living

  Biotic factors:

  1. Food availability
  2. New predators
  3. New pathogens
  4. Competition
• 9.3 Interdependence

  Interdependence = how organisms in a community depend on other organisms for vital services

  Stable community = abiotic and biotic factors are in balance
• 9.4 Parasitism and Mutualism

  Some species live together in a symbiotic relationship:

  2 types of symbiotic relationship:

  1. Parasite - if a smaller species lives directly on a larger species, and benefits at the expense of the other species
  2. Mutualistic relationship - it provides some benefit to the other species, for instance providing nutrients
• Transects and Quadrats


  Tool used in fieldwork to determine biodiversity
• Determining biodiversity of an area

  1. Measure every single species

  2. Take a sample and use to estimate entire population
• Sampling method


  • Takes significantly less time
  • Less risk of error
• Sampling method

  1. Divide field into 100 equal 1m x 1m squares

  2. Use random number generator to select a square

  3. Place 1m x 1m quadrat in selected square

  4. Count number of daisies

  5. Repeat 4 times, average 5 results

  6. Multiply average by 100 to estimate total population
• 9.7B Trophic Levels and Pyramids of Biomass

  Pyramids of biomass show the relative biomass at each trophic level

  • It shows the relative weights of material at each level
  • Less biomass as you move up the trophic levels
  • Not all food is consumed by an animal is converted into biomass
• 9.7B Trophic Levels and Pyramids of Biomass

  Producers transfer 1% of incident energy from light for photosynthesis - not all the light lands on the green (photosynthesising) part of the plant

  Only 10% of the biomass of each trophic level is transferred to the next

  • Not all biomass can be eaten
  • Not all the biomass eaten is converted into the biomass of the animal eating -
  • Glucose used in respiration, urea as a waste substance, biomass lost as faeces
• 9.8B Efficiency of Energy Transfers

  To calculate efficiency of biomass transfers between levels:

  (Biomass transferred to next level/Biomass available at previous level) x 100%