AQA A Level Biology复习笔记5.3.1 Primary Producers

• An ecosystem in a particular area includes:
  • All the living components (i.e. biotic factors such as organisms and their interactions)
  • All the non-living components (i.e. abiotic factors such as temperature and rainfall)

   

• All ecosystems include (and depend on) primary producers
  • Primary producers are organisms that make their own glucose
  • For example, plants and algae produce glucose via photosynthesis
  • Even deep-sea ecosystems such as those around hydrothermal vents (where there is no light) depend on primary producers (in this case bacteria) that use a process known as chemosynthesis to make glucose from the chemicals released from these vents

   

• In ecosystems where sunlight and water is available, the process of photosynthesis enables plants to synthesise organic compounds (glucose and other sugars) from carbon dioxide
  • In terrestrial (land-based) ecosystems, plants use CO₂ from the atmosphere
  • In aquatic (water-based) ecosystems, plants use CO₂ dissolved in the water

   

• The process of photosynthesis transforms light energy into chemical energy held in biological molecules
• The chemical energy in these biological molecules can then be used by other organisms within the community known as consumers (i.e. the organisms in higher trophic levels)
  • Primary consumers (herbivores or omnivores) feed on producers
  • Secondary consumers (carnivores or omnivores) feed on primary consumers
  • Tertiary consumers (carnivores or omnivores) feed on secondary consumers

   

Trophic levels for a simple food chain - the blue arrows show how the chemical energy originally produced by the primary producer (grass) is transferred to other organisms in the community