B16 and B17

• Population


  All organisms of the same species living with one another in a habitat
• Community


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


  The community of organisms (biotic) and non-living (abiotic) components of an area + their interactions
• Interdependence


  The dependence of different organisms on each other for survival, including food, shelter and reproduction
• The removal or addition of a species can affect the populations of others greatly
• Stable community


  Where all the biotic and abiotic factors are in balance
• Abiotic factors


  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
  • Wind intensity and direction
  • Carbon dioxide levels
  • Oxygen levels
• Abiotic factors


  Non-living factors
• Biotic factors


  Living factors
• Food availability


  More food means organisms breed more successfully
• Impacts of new species introduction

  • New predators
  • New pathogens
  • Interspecific competition
• Types of adaptation


  • Structural
  • Behavioural
  • Functional
• Structural adaptations


  • Sharp teeth of a carnivore
  • Camouflage
  • Thick layer of fat for insulation
• Functional adaptations


  • Late implantation of embryos
  • Conservation of water through producing little sweat
• Producers


  Photosynthetic organisms at the start of the food chain that provide biomass for all living things
• In a food chain, it is then the primary consumers (often herbivores), then secondary consumers, and finally tertiary consumers
• Transects and quadrats are used to work out the distribution and abundance of species in an ecosystem
• The carbon cycle


  1. CO2 is removed from the air in photosynthesis by green plants and algae

  2. CO2 is returned to the air when plants, algae and animals respire

  3. CO2 is returned to the air when wood and fossil fuels are burnt (combustion)
• The water cycle


  1. The sun's energy causes water to evaporate, forming water vapour

  2. Water vapour is also formed as a result of transpiration in plants

  3. Water vapour rises and then condenses to form clouds

  4. Water is returned to the land by precipitation
• Decomposition


  The breakdown of dead material into simpler organic matter
• Factors affecting decomposition rate

  • Temperature
  • Water
  • Availability of oxygen
• Anaerobic decay produces methane gas
• Biogas generators use anaerobic decay to produce methane for use as a fuel
• Investigating the effects of temperature on decay by measuring the pH change of fresh milk in the presence of the enzyme lipase


  1. Make a solution of milk and phenolphthalein indicator

  2. Add sodium carbonate to make the solution alkaline and pink

  3. Place the tube in a water bath at a specific temperature

  4. Add the lipase enzyme and start the stopwatch

  5. Time how long it takes for the pink to disappear (pH decrease)

  6. Repeat at different temperatures
• Producers produce and 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
• Reasons for biomass loss between trophic levels

  • Not all biomass can be eaten
  • Lots of glucose is produced during respiration, which produces CO2
  • Urea in urine
  • Faeces
• Biotic factor


  Living factors
• Biotic factors


  • Food availability
  • New predators
  • New pathogens
  • Interspecific competition
• Environmental changes that affect the distribution of organisms:

  • Temperature
  • Water availability
  • Atmospheric gas composition
• Behavioral adaptations

  • Individuals may play dead
  • Basking (lying) in the sun to absorb heat
  • Courting behavior to attract mate