Organisms and their environment

• Biomass


  The total mass of organic material measured in a specific area over a set period
• Carbon cycle

  The cycle through which carbon (in the form of carbon dioxide) moves between living organisms and the environment. It involves respiration, photosynthesis, feeding, combustion, decomposition and fossilisation
• Carnivore


  An animal that feeds on other animals
• Combustion

  The scientific term for the burning of a substance
• Community


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


  A process in the water cycle in which water vapour in the air cools and condenses into water droplets, forming clouds
• Consumers


  Organisms that feed on other organisms to obtain energy
• Deamination

  A process that occurs in the liver in which the amino group is removed from amino acids to produce ammonia, later converted to urea
• Death phase


  A period of population reduction in which the mortality rate is greater than the reproduction rate
• Decomposers

  Organisms that obtain energy via the breakdown of dead plant and animal material into simpler organic matter
• Decomposition

  The breakdown of dead materials into simpler organic matter
• Deforestation


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

  The conversion of nitrate ions to nitrogen gas by denitrifying bacteria
• Denitrifying bacteria


  Microorganisms responsible for the conversion of nitrate ions to nitrogen gas
• Ecosystem


  The community of organisms and non-living components of an area and their interactions
• Evaporation

  The process by which water is transformed from a liquid into a gas
• Food chain


  Describes the feeding relationships between organisms and the resultant stages of biomass transfer
• Food chain


  1. producer

  2. primary consumer

  3. secondary consumer

  4. tertiary consumer
• Food web


  A diagram showing the interactions of different food chains
• Fossil


  The remains of dead organisms found in rocks which are millions of years old
• Fossil fuel

  A fuel (eg. coal, oil, natural gas) formed from the compression of carbon-containing plant or animal remains over millions of years
• Fossilisation


  The process by which a fossil is formed
• Herbivore


  An animal that feeds on plants
• Ingestion


  The process by which organisms take food and drink into their bodies through the mouth. In a food chain, energy is transferred between organisms by ingestion
• Lag phase


  A period of slow population growth
• Light energy


  The main source of energy input to biological systems that is harnessed from the sun. Light energy is trapped by photosynthetic organisms and converted to chemical energy
• Log phase


  A period of rapid population growth, characterised by the birth rate exceeding the death rate. Also known as the exponential phase
• Nitrification


  The conversion of ammonium ions to nitrate ions by nitrifying bacteria. This takes place in two stages: ammonium ions are oxidised to nitrite ions; nitrite ions are oxidised to nitrate ions
• Nitrifying bacteria


  Microorganisms found in the soil responsible for the conversion of ammonium ions into nitrite and then nitrate ions
• Nitrogen cycle

  The cycle through which nitrogen moves between living organisms and the environment, involving four types of bacteria: decomposers, nitrifying bacteria, nitrogen-fixing bacteria and denitrifying bacteria
• Nitrogen fixation

  The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes. It can also occur via lightning
• Nitrogen-fixing bacteria

  Microorganisms responsible for the conversion of atmospheric nitrogen gas into nitrogen-containing compounds. They can be free-living or mutualistic
• Over-harvesting


  The harvesting of a species (for food, materials etc.) resulting in a reduction in population numbers. This may lead to the species becoming endangered or extinct
• Photosynthesis


  A reaction that takes place inside photosynthetic organisms (eg. plants, algae) and manufactures carbohydrates from raw materials using light energy
• Population


  All organisms of the same species living with one another in a particular habitat, at the same time
• Population growth curve


  A graphical representation of changing population numbers over time. The curve of a growing population in an environment with limited resources has a sigmoidal shape
• Precipitation


  A process in the water cycle in which water is released from clouds as rain or snow
• Predators

  Consumers that prey on and eat other animals
• Prey


  Animals that are eaten by predators
• Primary consumers


  Herbivores at trophic level two of a food chain that consume producers