Nutrient Cycling
ஊட்டச்சத்து சுழற்சி
Nature does not waste. Every atom of Carbon or Phosphorus in your body has been recycled through the biosphere for billions of years. If nutrient cycling stops, the ecosystem collapses instantly. Understand this flow, or you lose marks on basic biological thermodynamics.
The idea
Nutrient cycling, or biogeochemical cycling, is the movement of nutrient elements through the biotic and abiotic components of an ecosystem. These are classified into gaseous cycles, where the reservoir is the atmosphere or hydrosphere, like Carbon and Nitrogen. Sedimentary cycles have the Earth's crust as the reservoir, exemplified by Phosphorus and Sulfur. The rate of release of these nutrients is regulated by environmental factors like moisture, pH, and temperature.
Why it matters
It ensures the continuous availability of essential elements for life, as the Earth has a finite supply of nutrients.
NEET lens
NEET focuses on the reservoir location for specific elements. Memorize that Carbon and Nitrogen are gaseous, while Phosphorus and Sulfur are sedimentary. Expect questions matching the element to its reservoir type. Do not confuse the 'standing state' with the 'standing crop'.
Clinical significance
Disruption in the Phosphorus cycle leads to eutrophication, causing algal blooms that deplete dissolved oxygen, killing aquatic life. In the human body, a failure in mineral homeostasis—specifically Calcium and Phosphorus regulation—leads to metabolic bone diseases like Osteomalacia. Nature’s balance is your body’s balance.
Introduction
The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling (biogeochemical cycling). The amount of nutrients present in the soil at any given time is the standing state.
Core concept
Types: gaseous cycles — reservoir in the atmosphere (e.g. nitrogen, carbon); sedimentary cycles — reservoir in Earth's crust (e.g. sulphur, phosphorus). Environmental factors such as soil, moisture, pH and temperature regulate the rate of release of nutrients into the atmosphere. The function of the reservoir is to meet the deficit that occurs due to imbalance in the rate of influx and efflux. Standing state varies in different kinds of ecosystems and also on a seasonal basis. Carbon cycle: carbon constitutes 49 per cent of the dry weight of organisms; 71 per cent of carbon is found dissolved in oceans; about 4 × 10^13 kg of carbon is fixed in the biosphere through photosynthesis annually. Phosphorus cycle: the natural reservoir of phosphorus is rock; there is no respiratory release of phosphorus into the atmosphere (unlike carbon), and atmospheric inputs of phosphorus through rainfall are much smaller than carbon inputs. The gaseous exchange of phosphorus between organisms and environment is negligible.
Go deeper
Nutrients are never lost from the ecosystem; they are recycled again and again indefinitely — unlike energy, which flows one way.
From Class 10
Elements like carbon and nitrogen go round and round — from air or soil into living things and back again.