Food Chains WebsFood Chains Webs

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another.

• Trophic Levels (पोषण स्तर): Organisms in a food chain are categorized into steps called trophic levels. Producers (T1) form the base, followed by Primary Consumers/Herbivores (T2), Secondary Consumers/Carnivores (T3), and Tertiary/Top Carnivores (T4).
• Grazing Food Chain (चारण खाद्य श्रृंखला): Starts with green plants (producers) at the base and goes to herbivores and then to carnivores. It is directly dependent on an influx of solar energy.
• Detritus Food Chain (अपर्णा खाद्य श्रृंखला): Begins with dead organic matter (detritus) consumed by detritivores and decomposers (fungi and bacteria), then passes to carnivores. It is less dependent on direct solar radiation.
• Lindeman's 10% Law (लिंडमैन का 10% नियम): Only about 10% of the energy is transferred from one trophic level to the next; the remaining 90% is lost to the environment as heat during metabolic processes (respiration).

Food webs represent the complex, interconnected network of multiple food chains within a single ecosystem.

• Definition & Complexity (परिभाषा एवं जटिलता): Unlike a simple linear food chain, a food web provides alternate pathways for energy flow, making the ecosystem much more stable and resilient to environmental shocks.
• Omnivores in Food Webs (सर्वभक्षी): Organisms like humans, bears, and pigs that feed on both plants and animals occupy multiple trophic levels simultaneously, increasing web interconnectivity.
• Keystone Species (कीस्टोन जातियाँ): Species that have a disproportionately large effect on their natural environment relative to their abundance (e.g., tigers, sea otters, elephants). Their removal collapses the food web.

Graphical representations of the trophic structure and function of an ecosystem, spanning numbers, biomass, and energy.

• Pyramid of Numbers (संख्या का पिरामिड): Usually upright (grassland/forest), but can be inverted in a parasitic food chain where a single large tree supports countless parasites and hyperparasites.
• Pyramid of Biomass (बायोमास का पिरामिड): Upright in terrestrial ecosystems (plant biomass exceeds consumer biomass). However, it is inverted in aquatic ecosystems where phytoplankton (small biomass) support a larger standing crop of zooplankton.
• Pyramid of Energy (ऊर्जा का पिरामिड): Always upright. Energy decreases at each successive trophic level due to metabolic dissipation, strictly adhering to thermodynamic laws.

The escalating concentration of toxic chemicals as they move up the food chain.

• Bioaccumulation (जैव संचय): The accumulation of substances, such as pesticides or heavy metals, in an organism over time from the surrounding environment or diet.
• Biomagnification / Biological Amplification (जैविक आवर्धन): The progressive increase in concentration of persistent toxins (like DDT, Mercury, PCBs) at each higher trophic level because non-biodegradable toxins cannot be metabolized or excreted.
• Classic Examples (प्रमुख उदाहरण): Minamata disease (Mercury poisoning in fish-eating humans) and thin eggshells in fish-eating birds caused by DDT biomagnification.