Question

Most natural food chains are only four or five links long. The number of trophic levels is limited because

• A. There are more predators than herbivores
• B. Winter kills off most insects and stops the food chains
• C. The efficiency in utilizing the food eaten at each level is very low
• D. All of the above

Answer 1

The correct option is C The efficiency in utilizing the food eaten at each level is very low

• In an ecosystem biotic organisms form a food chain due to their feeding habit. All heterotrophic organisms are directly or indirectly drawing energy from autotrophic green plants.
• The energy that flows along the food chain is actually trapped solar energy, which is converted into chemical energy by plants and hence, regarded as producers in an ecosystem.
• When all biotic organisms of food chain are represented on different trophic levels we would realise that the number of trophic levels in an ecosystem could be limited to four, rarely five.
• This is because only 10% of the energy from producers get transferred to the level of primary consumers; likewise only 10% of the energy fixed as animal flesh can be transferred to the secondary consumers.
• Thus very little energy could be actually available for top consumers at the end of the food chain.
  

So the correct option is 'the efficiency in utilizing the food eaten at each level is very low'.