Energy Flow in Ecosystems (HL IB Biology)

• Photosynthesis is the process of converting light energy into chemical energy
  • Light energy is used by plants to power several processes which result in the production of organic molecules, or carbon compounds, including:
    • Glucose, which is used in respiration or stored in plant cells in the form of starch
    • Lipids
    • Amino acids
• Chemical energy, stored in carbon compounds in plant tissues, is passed to the primary consumer when the plant is ingested
  • The primary consumer digests the plant tissues and absorbs the carbon compounds containing stored chemical energy
  • These carbon compounds can either be used to fuel respiration or to build up animal tissue, meaning that the stored chemical energy is transferred to the tissues of the primary consumer
• When the primary consumer is ingested, the carbon compounds in its tissues, along with their stored chemical energy, pass to the secondary consumer, and so on up the food chain
• When an organism dies, the chemical energy stored in carbon compounds in its tissues passes to detritivores and saprotrophs

Food chains

• Food chains shows the feeding relationships between the organisms in an ecosystem
• In a food chain, the arrows represent the transfer of energy, in the form of stored chemical energy in carbon compounds, from one trophic level to the next, by the process of feeding
• Food chains also show the transfer of biomass between trophic levels

Food chain diagram

The arrows in a food chain represent the transfer of energy

Food webs

• Food webs show how several food chains within an ecosystem are connected
• In a real ecosystem, most species will have more than one food source, and will become food for more than one consumer species

Food web diagram

Food webs show the connections between food chains in an ecosystem