Ecosystems

• Define ecology

  The study of relationships between organisms and the environment
• Define population

  All the organisms of the same species within a habitat or an area
• Define habitat

  Where an organism lives
• Define ecosystem

  All the living organisms and physical factors in a habitat
• Define niche

  The role of an organism in an ecosystem
• Define community

  All the living organisms in an area
• Ecological efficiency - efficiency with which biomass/energy is transferred from one trophic level to another
• Biomass - mass of living material present in a particular place/organism
• How do you measure biomass?

  Kill and dry organism

  Measure dry mass
• Net production - The total amount of energy converted into biomass energy available to the next trophic level
• How energy can be lost at consumer level:

  • Not all of the organism is eaten
  • Heat loss
  • Movement
  • Maintaining body temperature
  • Waste (egestion and excretion)
  • Respiration
• How to improve primary productivity:

  • Crop rotation
  • Pesticides
  • Control temperature
  • Herbicides
  • Plant crops early
  • Fungicides
• How to improve secondary productivity:

  • Harvest animals prior to adulthood
  • Steroids
  • Selective breeding
  • Antibiotics
  • Intensive farming
• What abiotic factors affect the size of a population?

  Light

  Temperature

  pH

  Water availability
• What biotic factors affect population size?

  Interspecific competition

  Intraspecific competition

  Predation
• Nitrification

  • Converts NH4 + to NO2 - (by nitrosomonas)
  • Converts NO2 - to NO3 - (by nitrobacters)
  • Requires oxygen
• What is carrying capacity?

  The maximum population size that an ecosystem can support
• Ammonification

  • Converts NO2 - to NH4 +
  • Carried out by decomposers
• Nitrogen fixation

  • N2 + 3H2 -> 2NH3
  • NH3 ->NO3-
  • Carried by rhizobium
  • Symbiotic as plants get amino acids and bacteria ge carbohydrates
  • Occurs in anaerobic conditions
• Denitrification

  • Converts NO3- to N2
  • Carried out by pseudosomonas
  • Occurs in anaerobic conditions
• Predation


  Where an organism kills and eats another organism
• Conservation


  Maintenance of biodiversity through human action of management
• Preservation 


  Protection of an area by restricting or banning of human interference, so the ecosystem can stay in its original state
• Reclamation 


  Restoring ecosystems that have been damaged or destroyed by trying to restore biodiversity
• Finite resources


  Resources that are used up at a faster rate than can be replaced
• Aims of sustainability

  • Preserve environment
  • Ensure all resources available
  • Allow comfortable living
  • Create balance of consumption of sustainable resources
  • Enable countries to develop
• Sustainable resource


  A renewable resource that is being economically exploited but not being used up
• Techniques used to preserve fish populations

  Fishing quotas

  Nets with different mesh sizes

  Stop fishing in breeding season

  Fish farming