ENVIRONMENTAL STUDIES(ES)

ENVIRONMENTAL STUDIES

Lesson 11: Energy flow in an ecosystem, ecological succession

Introduction

The study of the flow of energy through the ecosystem is known as Ecological Energetic. The flow of energy that occurs along a food chain is called energy flow. All organisms in an ecosystem function as a result of the energy which they get from the energy flow. The ecosystem maintains itself and has stability through the process of energy flow.

Energy enters the food chain at the level of the producers (plants) in the form of solar energy. The plants convert solar energy into chemical energy in the process of photosynthesis, to form new plant material, i.e. leaves, flowers, fruit, branches, trunks and roots of plants. Since plants can grow by converting the sun’s energy directly into their tissues, they are known as producers in the ecosystem. The plants are used by herbivores as food, which gives them energy. A large part of this energy is used up for the metabolic functions of these animals such as breathing, digesting food, supporting growth of tissues, maintaining blood flow and body temperature. Energy is also used for activities such as looking for food, finding shelter, breeding and rearing the young ones. The carnivores, in turn, depend on the herbivores on which they feed .

Thus chemical energy is passed from one trophic level to the next through feeding. Since a large amount of heat energy is lost due to respiration, a food chain does not normally consist of more than five trophic levels. The fifth trophic level does not contain enough energy to support further levels. There is only about ten per cent of total energy of a trophic level is available to a succeeding trophic level. Energy is also lost from the food chain in excretory products and the remains of dead organisms; this is converted into heat energy by the action of decomposers. Energy flow is always unidirectional and non-cyclic, where as nutrient movement is cyclic.

Thus energy flow in the ecosystem can be summarized as

1. Energy is neither created nor destroyed. It is converted to different forms. Green plants are actually converters of energy and not producers.
   
2. The transfer of energy in an ecosystem is a cyclic process
   
3. There is a gradual loss of energy at each trophic level.