Ecosystems 6.3.1

• ecosystem 


  Biological community of interacting organisms and their physical environment
• population 


  organisms of a single species in a habitat
• community 


  organisms of all species in a habitat
• niche

  role of species in an ecosystem
• trophic level

  each stage of the food chain
• how are ecosystems dynamic?

  they are constantly changing due to many factors affecting te population of different organisms and environmental conditions are constantly changing
• what are the 3 types of changes in an ecosysthem affecting population size?

  • cyclic
  • directional
  • unpredictable
• what is a cyclic change?

  repeats itself in a rhythm eg movement of tides
• what is directional change?

  goes in one direction and lasts a long time eg coastal erosion
• what is an unpredictable change?

  no rhythm or direction eg hurricanes
• what 2 types of factors affect ecosystems

  • abiotic (non-living)
  • biotic (living)
• Biotic factors include…

  • Producers, autotrophs make their own organic matter eg plants they are the start of the food chain and are crucial for the survival of other organisms
  • consumers, heterotrophs can’t make their own organic matter either primary secondary or tertiary consumers
  • decomposers, saprotrophs cant make their own organic matter eg bacteria and fungi which feed on dead organic matter
• how are detritivores and decomposers involved in recycling of nutrients ?

  • Detritivores feed on detritus, dead decaying matter they digest into smaller fragments which increases the surface area and are passed out as faeces
  • this is further digested by decomposers, saprotrophs which feed on DOM eg fungi or bacteria
  • decomposes digest externally by extra cellular digestion by releasing enzymes onto the DOM, they break down large organic molecules into smaller ones and use this for energy and growth
  • this process releases mineral ions, inorganic compounds and elements into env reused
• What does it mean by trees and peat bogs acting as “carbon sinks”

  • Trees use co2 to make sugars and organic molecules via photosynthesis some of this is used for growth
  • lot of carbon in these molecules are locked in the tree till it dies co2 is then released by decomposes in respiration
  • peat bogs are more acidic, anaerobic decomposes cannot survive there any DOM remains as co2 is not released by decomposers respiring
• what effect does aerating the soil have on the carbon cycle

  • helps increase oxygen concentration in the soil
  • promotes activity of decomposes respiring areobically therefore DOM will be broken down faster and carbon will be recycled faster
• why do farmers use fertilisers?

  • crops are not recycled they are taken away to consume
  • fertilisers can be organic eg manure containing DOM which decomposes to release ammonia into soil
  • inorganic fertilisers usually contains nitrates or ammonium ions
• what happens if more fertiliser is added than the plant can take up

  • when it rains excess fertilisers was into streams and rivers- leaching
  • extra nutrients causes algae to grow faster blocking sunlight so plants will die, decomposed by microbes that respire so the oxygen is used up and aquatics will suffocate and die