Energy Flow Through an Ecosystem

• Producers, Consumers and Decomposers


  • Nutrients and energy are transferred from producers to consumers to decomposers through feeding
  • Types of consumers : primary, secondary, tertiary
• Food Chain


  • A food chain is a series of organisms, beginning with the producer, through which energy and nutrients are transferred.
• Trophic Level


  • An organism’s trophic level is the position it occupies in a food chain.
• Food Web


  • A food web consists of a network of interconnected food chains.
• Producers


  • Producers are organisms that make their own food
  • may have chlorophyll to trap and convert light energy into chemical energy stored in glucose during photosynthesis.
• Consumers


  • Consumers are organisms that are not able to make their own food.
  • obtain nutrients and chemical energy directly from another organisms through feeding.
• Decomposers


  • Decomposers obtain nutrients and chemical energy directly from breaking down organic matter (e.g. faeces, urine, dead organism).
  • some nutrients are also returned to the environment in the process.
• non-cyclical nature of energy flow

  • Sun is the principal source of energy.
  • Producers convert light energy from the Sun into chemical energy during photosynthesis.
  • Energy flows as chemical energy through the trophic levels in the food chain.
  • Non-cyclical: energy does not return to the same system or organism
  • Both producers and consumers carry out respiration. Some chemical energy is converted to heat energy which is lost to the environment.
  • Since living organisms are unable to use heat energy to do work, heat energy does not return to the food chain.
• Energy Loss in food chain

  • Both producers and consumers carry out respiration. Some chemical energy is converted to heat energy which is lost to the environment.
  • Organic matter (e.g. uneaten body parts, egested material, excreted materials) contains trapped chemical energy that is not passed on to the next trophic level
• efficiency of energy transfer

  • 90% of energy is lost at each trophic level, only 10% of the energy is passed to next trophic level
  • Hence, total amount of energy decreases as we move along the trophic levels due to energy loss
  • Most food chains are short with at most 4 trophic levels
  • Short food chain ensures that organisms in lower trophic levels provide sufficient energy to support organisms in higher trophic levels
  • Short food chains have less energy loss since that is fewer trophic levels. Hence, more energy is available for final consumer and more energy efficient.