M6:S6 Ecosystems

• Habitat


  The place where an organism lives, e.g. a rocky shore or a field
• Population


  All the organisms of one species in a habitat
• Producer


  An organism that produces organic molecules using sunlight energy, e.g. plants
• Consumer


  An organism that eats other organisms, e.g. animals and birds
• Decomposer


  An organism that breaks down dead or undigested organic material, e.g. bacteria and fungi
• Habitat


  The place where an organism lives, e.g. a rocky shore or a field
• Population


  All the organisms of one species in a habitat
• Producer


  An organism that produces organic molecules using sunlight energy, e.g. plants
• Consumer


  An organism that eats other organisms, e.g. animals and birds
• Decomposer


  An organism that breaks down dead or undigested organic material, e.g. bacteria and fungi
• Trophic level


  A stage in a food chain occupied by a particular group of organisms, e.g. producers are the first trophic level in a food chain
• An ecosystem is all the organisms living in a certain area and all the non-living conditions (factors) found there
• An ecosystem is a dynamic system - this means it's changing all the time
• Biotic and abiotic factors


  • Biotic factors - The living features of an ecosystem
  • Abiotic factors - The non-living features of an ecosystem
• Biotic factors in a rock pool ecosystem


  • Seaweed can be a food source for consumers such as limpets that graze on this producer
  • Intense competition for food (such as seaweed) can limit the number of organisms that are present in a small rock pool ecosystem
• Abiotic factors in a rock pool ecosystem


  • At high tide they are completely submerged by the ocean so experience similar abiotic factors (e.g. pH, salinity, temperature, etc. to the ocean ecosystem
  • At low tide they experience more extreme abiotic conditions (e.g. higher salinity and temperatures-only some organisms can tolerate these conditions
• Biotic factors in a playing field ecosystem


  • Producers include grass and other plants such as daisies, clover and dandelions
  • The large amount of these plants might attract a large number of organisms that use them as a food source (e.g. rabbits, caterpillars)
• Abiotic factors in a playing field ecosystem


  • Rainfall and sunlight affect the growth of the producers in the ecosystem
  • In a very wet year, the soil may become waterlogged, making it difficult for plants to grow
• Biotic factors in a large tree ecosystem


  • Insects, such as caterpillars, can use the leaves of a tree as a source of food
  • If they consume all the leaves on a tree (detoliation) they can slow tree growth and even lead to its death
• Abiotic factors in a large tree ecosystem


  • Drought conditions (e.g. when there are prolonged periods of very low rainfall) can negatively impact the growth of a tree
  • In severe cases it can result in the whole tree (or parts of it) dying
• The main route by which energy enters an ecosystem is photosynthesis (e.g. by plants)
• Biomass


  The mass of living material, e.g. the mass of plant material
• Energy is transferred through the living organisms of an ecosystem when organisms eat other organisms
• Trophic levels


  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
• Food chains show simple lines of energy transfer
• Food webs show lots of food chains in an ecosystem and how they overlap
• Energy locked up in the things that can't be eaten (e.g. bones, faeces) gets recycled back into the ecosystem by decomposers
• Ecosystem


  All the organisms living in a certain area and all the non-living conditions (factors) found there
• Ecosystems are described as being dynamic because they are changing all the time
• Biotic factor


  The living features of an ecosystem
• Biomass


  Energy is stored as biomass
• Not all the energy (e.g. from sunlight or food) that's available to the organisms in a trophic level is transferred to the next trophic level
• Around 90% of the total available energy is lost in various ways
• Ways energy is lost


  • Some is never taken in by the organisms in the first place
  • Some parts of food aren't eaten by organisms so the energy isn't taken in
  • Some parts of food are indigestible so pass through organisms and come out as waste
• Gross productivity


  The rest of the available energy (40%) that is taken in/absorbed
• Respiratory loss


  30% of the total energy available (75% of the gross productivity) is lost to the environment when organisms use energy produced from respiration for movement or body heat
• Net productivity


  10% of the total energy available (25% of the gross productivity) becomes biomass (e.g. it's stored or used for growth)
• Net productivity or biomass is the amount of energy that's available to the next trophic level
• Calculating net productivity


  Gross productivity - Respiratory loss = Net productivity
• Energy transfer efficiency


  The percentage of energy transferred from one trophic level to the next