As we know, the sun is the only source of energy in all the ecosystems on earth except the deep-sea hydrothermal ecosystem. Less than 50% of the solar radiation is photosynthetically active radiation, which is called PAR. Plants capture 1 to 10% of photosynthetically active radiation. It is very important to get knowledge about how the energy is captured by plants by different organisms of the ecosystem. The chemical energy of food is one of the primary sources of energy that is required by all living organisms on earth. This energy is transferred to different trophic levels.
The energy flow has 2 laws of thermodynamics. Plants as a producer absorb sunlight with the help of chloroplast and some of its parts get converted into chemical energy by the process of photosynthesis. The first law of thermodynamics states that energy is neither created nor destroyed; it can only be transferred from one form to another. The second law of thermodynamics states that the isolated system entropy always increases.
The different producers and consumers are classified into different groups, which are known as tropical levels. The producer is the first trophic level of the ecosystem. The green plant is called a producer. Herbivorous is placed at the second trophic level. Primary carnivores represent the third trophic level and tertiary consumers are at the last level. Herbaceous and Woody plants are the major producers in a terrestrial ecosystem and phytoplankton algae and higher plants are the producers in aquatic ecosystems.
All the animals depend on the plant for their basic needs so they are known as consumers or heterotrophs. If these animals feed on the plants, then the plants are referred to as producers, and animals are known as primary consumers. The energy is transferred from one level to another, so no energy traps into an organism that remains forever. If the animal eats other animals which eat the plants or plant products, then these are called secondary consumers. The primary consumer is herbivorous. Some examples of herbivores are birds, insects, and mammals, mollusks, etc. The consumers who feed on herbivores are known as carnivores or primary carnivores.
1. GFC or grazing food chain- It is a normal food chain in which plants are the producers. Energy flows from one trophic level to another; that is, from producer to primary consumers than to the secondary consumer. GFC plays a major role in aquatic and terrestrial ecosystems. At some level, the detritus food chain also gets connected with the grazing food chain.
2. DFC or Detritus food chain- In this food chain, the dead matter occupies the lowest level of the food chain which is followed by decomposers. This food chain comprises a decomposer, which are heterotrophic organisms like bacteria and fungi. They get their energy from the dead decaying organic matter called detritus. These decomposers secrete digestive enzymes which help to break down the dead and waste material into a simple form.
3. PFC or Parasitic food chain- In which food chain large organisms are exploited and the food transfers to smaller organisms.
It is important to know that energy decreases at different trophic levels. When an organism dies it is converted into dead biomass or detritus which results in an energy source for the decomposers. Each topic level has some mass of living material at a particular time which is known as standing crop. The standing crop is measured as the total dried biomass of the living organism present in an environment. This biomass is expressed in terms of dry weight or freshness.
The energy transfer on each trophic level is based on the 10% law. According to this law, 10% of energy is transferred from one level to another trophic level. The measurement of biomass is more accurate in dry weight.
Energy flow is important in the ecosystem due to the following reasons -