All organisms need energy. They acquire energy from the food that they consume. Also, the most important way by which energy is procured is predation. Energy is required for proper growth, development, and maintenance of the cells and tissues. Moreover, all the processes occurring inside a living system require energy. In most ecosystems, the ultimate source of energy is the sun. Plants capture solar energy, carry out the process of photosynthesis; and hence, produce their food. The transfer of energy encompasses infinite interactions and relationships. A food chain describes the transfer of energy in the form of food, from one organism to another. The flow of energy through the ecosystems occurs by way of a food web. A food web includes a number of food chains. However, a food chain illustrates the direct transfer of energy between the living organisms. Since most of the organisms feed on different things, therefore, a food web is much more practical in its approach and renders a simplified view of the transfer of energy in an ecosystem. How efficiently the energy is transferred from one trophic level to the next is described by ecological efficiency.
The energy pyramids exhibit the flow of energy. Energy flows from one level to another when an organism from the higher level consumes/eats an organism from the lower level. Different organisms occupy different positions in the food chain; depending upon their source of food and nutrition, and this is what is known as the trophic level.
Producers are the organisms who synthesize their own food. The producers lay the foundation for all the food chains. Examples of the producers are plants, algae, and a few bacterial species. Producers synthesize their own food through the process of photosynthesis; whereby sunlight is converted into chemical energy. The energy from the sunlight is converted into carbon-dioxide, glucose, and water. The glucose produced in the reaction of photosynthesis is, hence, broken down to produce energy. The primary producers occupy the basal or the bottom level of the pyramid of energy.
Consumers are the organisms which cannot synthesize their own food; therefore, they consume other organisms. Consumers are also known as herbivores, carnivores, and omnivores.
- Primary Consumers: Also known as herbivores, the primary consumers eat the producers. The primary consumers occupy the second level of the energy pyramid. The examples of primary consumers are chipmunks, mice, rabbits, horses, birds, deer, and some insects. In the case of an aquatic ecosystem, zooplankton, sea urchins, snails, and fish constitute the primary consumers. The primary consumers become the food source and fall prey to the organisms at the level higher on the food chain.
- Secondary Consumers: They are the organisms who eat primary consumers. They occupy the third trophic level of the energy pyramid. The secondary consumers are, sometimes, also known as carnivores and they usually consume meat. The examples of the secondary consumers are birds, fish, wolf, etc.
- Tertiary Consumers: The tertiary consumers are the ones who eat secondary consumers and, in some cases, also consume herbivores. These secondary consumers are themselves, the consumers of the primary consumers. Usually, they have no natural enemies; and also occupy the top-most position in the food chain. Some of the examples of the tertiary consumers are hawks, lions, etc.
The 10 Percent Energy Law
The transfer of the energy in the food chain is limited; and hence, the number of trophic levels in the food chain is limited. There is only 10 per cent of the transfer of energy from each lower trophic level to the next/higher trophic level. This law, known as the 10 per cent energy law, was proposed by Raymond Lindeman. The primary consumers do not acquire 100 per cent of the energy transfer from the plants/producers; some of the energy of the sun is consumed by the plants during the process of photosynthesis.
Where are humans placed on the food chain?
There are many consumers which feed on multiple trophic levels. Human beings become primary consumers when they consume producers like plants, fruits, etc. However, humans become secondary consumers when they consume primary consumers like lamb, salmon, etc.
Quick Revision in 5 Points
- The food chains describe the transfer of the energy from one organism to another.
- The energy pyramid represents the flow of energy from one trophic level to another.
- The producers synthesize their own food and lay the foundation stone for all food chains.
- The consumers (herbivores, carnivores, and omnivores) depend on producers and other organisms for food.
- The 10 per cent energy law states that there is only 10 per cent of the transfer of energy from one trophic level to another.
- Did you know that the percentage loss of energy due to respiration is progressively greater for higher levels in the food cycle?
- Although it is usually referred to as law, it’s merely an observation and only points out to the fact that the efficiency during the transfer of energy is less than 100 per cent.
- You might find it surprising that the 10 per cent value is not similar in all cases as it varies with different types of ecosystems.
- Did you know that the scientist who proposed this law, Raymond Lindeman, had met with an accident in his childhood that left him with a damaged cornea and a whitish cast as iodine fell into his right eye?