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How Nature Works in Harmony - Who Eats Whom?

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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An ecosystem consists of biotic (living) and abiotic (non-living) components working together in harmony.

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Producers (Autotrophs) are organisms like green plants that prepare their own food using photosynthesis: 6CO2+6H2O→SunlightC6H12O6+6O26CO_{2} + 6H_{2}O \xrightarrow{\text{Sunlight}} C_{6}H_{12}O_{6} + 6O_{2}.

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Consumers (Heterotrophs) depend on producers directly or indirectly for food. They are classified into herbivores, carnivores, and omnivores.

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A Food Chain is a linear sequence of organisms where each is eaten by the next member in the chain.

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Trophic Levels represent the functional levels in a food chain. T1T_{1} is the producer, T2T_{2} is the primary consumer, T3T_{3} is the secondary consumer, and so on.

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The 10% Law: Only 10%10\% of the energy available at one trophic level is transferred to the next level. The rest is lost as heat to the environment.

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Food Web: A network of interconnecting food chains in an ecosystem, providing alternative pathways for energy flow and ensuring ecosystem stability.

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Biological Magnification: The process where the concentration of non-biodegradable chemicals (like pesticides) increases at each successive trophic level.

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Decomposers like bacteria and fungi break down dead organic matter, recycling nutrients back into the soil, represented as Organic Matter→Nutrients+CO2+H2OOrganic \text{ } Matter \rightarrow Nutrients + CO_{2} + H_{2}O.

📐Formulae

6CO2+6H2O+Sunlight→ChlorophyllC6H12O6+6O26CO_{2} + 6H_{2}O + \text{Sunlight} \xrightarrow{\text{Chlorophyll}} C_{6}H_{12}O_{6} + 6O_{2}

Energy available to next level=10100×Energy at current level\text{Energy available to next level} = \frac{10}{100} \times \text{Energy at current level}

Energy Loss=90%×Total Energy at that level\text{Energy Loss} = 90\% \times \text{Total Energy at that level}

💡Examples

Problem 1:

In a food chain consisting of Grass →\rightarrow Grasshopper →\rightarrow Frog →\rightarrow Snake, if the Grass (Producer) has 20,000 J20,000\text{ J} of energy available from the sun, calculate the energy available to the Snake.

Solution:

  1. Energy at Producer level (Grass) = 20,000 J20,000\text{ J}.
  2. Energy at T2T_{2} (Grasshopper) = 10% of 20,000=2,000 J10\% \text{ of } 20,000 = 2,000\text{ J}.
  3. Energy at T3T_{3} (Frog) = 10% of 2,000=200 J10\% \text{ of } 2,000 = 200\text{ J}.
  4. Energy at T4T_{4} (Snake) = 10% of 200=20 J10\% \text{ of } 200 = 20\text{ J}.

Explanation:

According to Lindeman's 10% law, only 10%10\% of energy is passed to the next level. We calculate this step-by-step: 20000→10%2000→10%200→10%2020000 \xrightarrow{10\%} 2000 \xrightarrow{10\%} 200 \xrightarrow{10\%} 20

Problem 2:

Calculate the total energy lost to the environment if 5,000 J5,000\text{ J} is present at the herbivore level and it is consumed by a secondary consumer.

Solution:

Energy at Herbivore (T2T_{2}) = 5,000 J5,000\text{ J}. Energy transferred to Secondary Consumer (T3T_{3}) = 10%×5,000=500 J10\% \times 5,000 = 500\text{ J}. Energy lost = Total energy - Transferred energy. 5000−5004500\begin{array}{r} 5000 \\ - 500 \\ \hline 4500 \end{array} Total energy lost = 4,500 J4,500\text{ J}.

Explanation:

The energy lost to the environment as heat and used for metabolic processes is 90%90\% of the total energy at that specific level.