Biogeochemical cycles of matter
Large-scale processes of chemical element migration in the biosphere are studied by biogeochemistry. Cycles are classified according to the location of the element's main reservoir pool:
- Water cycle: an independent cycle of moisture movement in nature.
- Gaseous cycles: the atmosphere or hydrosphere serves as the reservoir pool. These include the carbon, nitrogen, and oxygen cycles.
- Sedimentary cycles: the reservoir pool is concentrated in the Earth's crust. This group includes the phosphorus, calcium, and iron cycles.
Structural components of the ecosystem
For an ecosystem to exist stably, there must be a clear division of roles within it. No single species is capable of maintaining the life cycle on its own. An ecosystem includes four mandatory components:
- Abiotic environment — a complex of natural and climatic factors. Includes soil, air, water, mineral compounds, and sunlight.
- Producers — creators of organic matter. Through photosynthesis or chemosynthesis, they convert inorganic substances into organic ones.
- Consumers — consumers of ready-made organic matter. They are divided into primary consumers (herbivores) and secondary, tertiary, and higher-order consumers (carnivores).
- Decomposers — destroyers. They feed on dead remains, breaking them down into mineral components. These include macro-organisms (worms, arthropods) and microorganisms (fungi, bacteria at the final stages of decomposition).
Functional organization: energy and matter
The full-fledged functioning of an ecosystem is based on two key processes:
- Energy flow (unidirectional). The initial source is solar energy captured by producers. It is then transferred along the food chain (herbivores $\rightarrow$ carnivores). At each trophic level, part of the energy is irreversibly lost as heat during organism respiration.
- Matter cycling (cyclic). Waste products and unused organic matter from all levels go to detritivores and decomposers. They process the substrate and return minerals in a form accessible to producers back into the biotope. The circle is closed.
The interaction of these groups enables the ecosystem to perform four main functions: synthesize organic matter, break it down, maintain energy flow, and carry out biogeochemical cycles.
Briefly: answers to topical questions
What are the main stages of the nitrogen cycle in the biosphere?
The main stages of the nitrogen cycle in the biosphere include processes of nitrogen fixation, transformation, and release with the participation of microorganisms. The following stages are distinguished:
- Nitrogen fixation — fixation of atmospheric nitrogen.
- Ammonification — formation of ammonia during protein breakdown by microorganisms; conversion of organic substances into ammonium compounds.
- Nitrification — formation of nitrites and nitrates during the breakdown of organic matter through the oxidation of ammonia to nitrous and nitric acids.
- Denitrification — reduction of nitrates with the release of free nitrogen.
What is the essence of the 10 percent rule (Lindeman's law) in energy transfer along a food chain?
The essence of the 10 percent rule (Lindeman's law) is that, on average, only 10% of energy is transferred from one trophic level to another. Energy in ecosystems does not cycle; rather, it flows in one direction and gradually dissipates as heat. Because energy runs out toward the end of the food chain, the length of such chains is typically limited to just 3–5 links.
What types of ecological pyramids exist?
There are three main types of ecological pyramids, which serve to visually demonstrate the efficiency of ecosystem functioning and the ratio of trophic levels. The following types are distinguished:
- Pyramid of numbers — demonstrates the number of individuals at each level.
- Pyramid of biomass — demonstrates the total mass of living matter.
- Pyramid of energy — demonstrates the flow of energy (in calories) and the efficiency of its utilization.
To easily remember the roles of living organisms, imagine a factory: Producers manufacture products (synthesize organics), Consumers consume them, and Decomposers reduce them (utilize waste and return raw materials to the assembly line).
Class and exam questions
What is the difference between a biocenosis and a biotope?
A biocenosis (from Lat. bios — life, koinos — together) is a community of interacting living organisms. A biotopes (from Lat. topos — place) is the physical space or territory where this biocenosis lives.
Why is the cycling of matter closed, while the flow of energy is not?
Substances constantly circulate between living organisms and the environment thanks to the work of decomposers. Energy, however, comes from the outside (from the Sun) and is gradually consumed, dissipating as heat during respiration at each trophic level.
What role do decomposers play in the biosphere?
Decomposers close the cycles of matter. They break down dead organic remains into simple mineral compounds, returning them to the biotope so producers can use them again.
What else to study on this topic
- Mechanisms of photosynthesis and chemosynthesis in producers
- Classification of consumers and food chains
- Sedimentary biogeochemical cycles (phosphorus, calcium, iron)
- Gaseous biogeochemical cycles (carbon, nitrogen, oxygen)
- Differences between macro- and micro-decomposers in the destruction process
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