Ecology

• Abiotic factors


  The non-living aspects of an ecosystem e.g. temperature, light intensity, moisture, wind direction, wind intensity, soil pH, soil mineral content, carbon dioxide levels and oxygen levels
• Adaptation


  A feature of an organism that increases its chance of survival in its environment. Such features may be behavioural, structural or functional
• Anaerobic decay


  Decomposition in the absence of oxygen (commonly occurring in waterlogged soils) that produces carbon dioxide and methane gas
• Apex predator


  A carnivore at the top of the food chain with no predators
• Biodiversity


  The variety of living organisms in an ecosystem
• Biogas


  A type of biofuel (methane gas) produced by anaerobic decay in biogas generators
• Biotic factors


  The living components of an ecosystem e.g. food availability, pathogens, predators and other species
• Carbon cycle


  The cycle through which carbon (in the form of carbon dioxide) moves between living organisms and the environment, involving respiration, photosynthesis and combustion
• Community


  All of the populations of different species living together in a habitat
• Competition


  When different organisms compete for the same resources (e.g. light, water, mates, territory) in an ecosystem. This limits population sizes and stimulates evolutionary change
• Compost


  Dead and decaying organic matter, commonly used as a fertiliser
• Decomposers


  Organisms that release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter
• Decomposition


  The breakdown of dead materials into simpler organic matter. The rate of decomposition is affected by temperature, water and oxygen availability
• Deforestation


  The removal of trees from land which is subsequently used to grow crops or provide space for cattle
• Distribution


  The spread of living organisms in an ecosystem. It is affected by environmental changes which may be seasonal, geographic or man-made
• Ecosystem


  The community of organisms (biotic) and non-living (abiotic) components of an area and their interactions
• Efficiency of biomass transfer

  The efficiency of biomass transfer between trophic levels is calculated using: [formula]
• Extremophiles


  Organisms that can live in extreme environments e.g. high temperatures, high salinity
• Food chain


  Describes the feeding relationships between organisms and the resultant stages of biomass transfer. It takes the form: producer ⟶ primary consumer ⟶ secondary consumer ⟶ tertiary consumer
• Community


  Many different populations interact in the same habitat
• Food security


  Ensuring that populations have access to adequate amounts of safe and nutritious food
• Ecosystem


  The interaction of a community with non-living (abiotic) parts of the environment
• Organisms


  • Adapted to live in the conditions of their environment
• Global warming


  The gradual rise in the average temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas
• Competition


  Can be within a species or between different species
• GM crops


  Crops that have had their genomes modified by the insertion of a desired gene from another organism
• Things plants may compete for

  • Light
  • Space
  • Water
  • Mineral ions
• Interdependence


  The dependence of different organisms on each other for survival e.g. plants depend on pollinators, herbivores depend on plants
• Things animals may compete for

  • Space
  • Food
  • Water
  • Mating partners
• Interdependence


  Organisms in a community depend on other organisms for vital services like food, shelter and reproduction
• Mean


  The average of a set of numbers calculated by dividing the sum of the values by the number of values
• The removal or addition of a species to the community can affect the populations of others greatly, as it changes prey or predator numbers
• Median


  The middle number in a list of values ordered from lowest to highest
• Stable community


  Where all the biotic (living) and abiotic (non-living) factors are in balance, resulting in population sizes remaining roughly constant
• Microorganisms


  Very small organisms involved in the recycling of materials in an ecosystem. They return mineral ions to the soil and convert carbon to carbon dioxide which is released into the atmosphere
• Abiotic factor


  A non-living factor
• Mode


  The number that occurs most commonly in a set of data values
• Abiotic factors that can affect a community

  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
  • Wind intensity and direction
  • Carbon dioxide levels
  • Oxygen levels for aquatic animals
• Mycoprotein


  A food high in protein (suitable for vegetarians) that is produced by the microorganism, Fusarium, in fermentation vats
• Biotic factor


  A living factor