6.3.1 - ecosystems

• The bacteria found in soil in the nitrogen cycle is azotobacter
• The bacteria found in root nodules in the nitrogen cycle is rhizobium
• The bacteria used in nitrification from ammonia to nitrites is nitrosomonas
• the bacteria used in nitrification from nitrites to nitrates is nitrobacter
• An ecosystem is all the living organisms found in one area and the non living aspects of their environment.
• Ecosystems are dynamic as they depend on interactions between biotic and abiotic factors.
• Examples of ecosystems are:

  rock pool

  tree

  field
• Biotic factors are the living features of an ecosystem

  eg, predators, disease
• Abiotic factors are the non living features of an ecosystem

  eg, light, temperature
• an ecosystem is all living and non living components and their interactions
• Population is the number of individuals of the same species, living in the same place at the same time.
• Community is all the organisms of all the different species living in a habitat
• Habitat is the place where an organism lives
• Niche is the role of an organism in the ecosystem
• Biotic factors are the effect of other living organisms
• abiotic factors involve the non living components of the environment
• Examples of biotic factors are

  • predation
  • competition
• in a rock pool abiotic factors include:

  • water availability
  • sunlight
  • ph of water
  • pollutants of water
• in a rock pool biotic factors include:

  • competition
  • parasitism
• in a tree abiotic factors include:

  • temperature
  • wind speed
  • humidity
  • ph of soil
• in a tree biotic factors include:

  • Inter or Intra specific Competition
  • parasitism
• the sun is the source of energy for almost all ecosystems. The suns light is concerted into chemical energy in plants which is transferred to other organisms as Food.
• A trophic level is a place in the food chain
• Producers fix carbon by using sunlight (photosynthesis)
• Producer -> primary consumer -> secondary consumer
• arrows in a food chain show the direction of energy transfer
• A pyramid of numbers has producers at the bottom with the longest rectangle and the top consumer (usually tertiary) at the top with the smallest rectangle
• biomass is the mass of living material in a particular food chain/web
• To calculate the biomass at each trophic level you multiply the number of organisms by their dry mass
• Biomass is measured in kg
• When measuring biomass it is an advantage to measure the dry mass as it allows a better comparison between different species
• when measuring biomass it is a disadvantage to measure the dry mass as it kills the organism
• To calculate the energy of the dry mass:

  use a bomb calorimeter

  burn the sample in a high pressure of oxygen

  the rise in the temperature of the water is measured
• Biomass decreases as you move up the trophic levels because:

  not all biomass is eaten (eg, bones And roots)

  some is transferred to the environment as heat

  some is excreted (eg urine or faeces)

  some is indigestible (eg, cellulose)
• Net primary production is the energy available at each trophic level.
• NPP (net primary production) is measured in Kj m-2 yr-1
• The efficiency with which biomass or energy is transferred from one trophic level to the next is called ecological efficiency.
• Factors that increase NPP are:

  • high temperature
  • increase in sunlight

  because the more photosynthesis that occurs the more storage of biomass
• Less than 3% of sunlight is converted into chemical energy. This is because not all light hitting leaves is absorbed, some can be Reflected, transmitted through the leaf or it is the wrong wavelength of light. Not all light hits the chlorophyll.
• Productivity is the rate at which the plant converts light energy into chemical energy