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UPSC » UPSC CSE Study Materials » NCERT Notes for UPSC 2025 » Food Chain, Food Web and Biogeochemical Cycles

Food Chain, Food Web and Biogeochemical Cycles

Food chain, food web, and biogeochemical cycles play a crucial role in photosynthesis and development of organisms.

Food Chain

  • The food chain connects the organisms in ecosystems. It refers to the eating sequence and energy transfer from small creatures to large predators. The food chain starts with  a producer, which a primary consumer eats. The primary consumer is then eaten by a secondary consumer, which in turn is consumed by the tertiary consumer
  • The flow of energy: The energy transfer from one level to another during the food chain process is known as energy flow

Food Web:

  • Food chains are identical as various organisms are interdependent. For example, a grain-eating mouse can be consumed by two or more different consumers (carnivores), and those carnivores can be eaten by tertiary consumers (high predatory animals). In such cases, carnivores can eat more than one species of predators. This interconnected network of species is known as the food web
  • Grazing food chain: In the veld feed chain, plants as producers are placed at the first level, whereas carnivores as consumers are in the last level. There is a loss of energy at each level due to respiration, expulsion, or rot
  • Detritus food chain: This chain is based on the grazing animals’ energy consumption, which involves breaking down the organic matter and dead organisms in the feed
  • The food chain, food web, and biogeochemical cycle are interconnected

Biogeochemical Cycles

  • The sun is the primary energy source of life on earth. This energy supports all living beings in the biosphere through photosynthesis. The food cycle starts from the green plants and leads to a food web
  • Green plants intake carbon dioxide during photosynthesis and convert it into organic compounds and oxygen
  • Only a tiny fraction of the energy gained from the sun is used in photosynthesis. More than half of the energy is consumed for plant respiration, and the remaining is stored or transferred to other parts of the plant
  • All living things breathe and live in diverse associations. The survival of all living organisations depends on systematic flows such as water, energy, and nutrients. These flows vary from one region to another.  The atmosphere and the hydrosphere contain approximately the same proportion of chemical components. Plant and animal tissues maintain this balance of chemical elements through a cyclic passage
  • The cycle begins with the absorption of chemicals by the body and ends by decomposition. Solar insolation enhances the processes in this cycle
  • The circular motion of the biosphere molecules between living organisms and the environment is known as a biogeochemical cycle

There are two types of biogeochemical cycles:

  1. Gaseous cycle: The atmosphere and the ocean are the main reservoirs of nutrients.
  2. Sedimentary cycle: Sedimentary and other rocks present in the earth’s crust are the main reservoirs.

The energy cycle starts with biogeochemical reactions and creates food chains and webs. Therefore, you need a clear picture of the food chain, food web, and biogeochemical cycles to understand any concepts.

Water Cycle

All living organisms maintain water circulation. The atmosphere and the lithosphere in the form of solid, liquid and gas is known as the water cycle or hydrologic cycle.

Other Mineral Cycles

  • Some minerals act as essential nutrients for plant and animal life. These are found in inorganic sources such as phosphorus, sulphur, calcium and potassium
  • They often occur as salt dissolved in water or lakes, streams and seas
  • Mineral salt is obtained directly from the earth’s crust by weathering, and the soluble salts reach the sea through a water cycle
  • Some salts return to the earth’s surface through sedimentation. After weathering, these salts enter the cycle again
  • All living things meet their mineral requirements in their natural environments. Animals find their mineral requirements by consuming plants and animals
  • Once the living organisms die, minerals are returned to the soil and water by decomposition and flow
  • This article clearly explains all the three concepts of the food chain, food web, and biogeochemical cycles

Conclusion

The food chain is a series of creatures that begins with producer organisms and ends with decomposer species. A food web is a network that connects several food systems. The food chain takes a single route, while the food web has several pathways. A food web is made up of several interrelated food chains. Nutrients are, in the end, chemical substances. As a result, there is this natural channel via which biological matter is continually cycled. Nutrients are never depleted in an ecosystem. These nutrients are recycled at every level. The recycling of nutrients via various components of an ecosystem is referred to as the nutrient cycle or biogeochemical cycle.