krit.club logo

How Nature Works in Harmony - How Does One Change Lead to Another?

Grade 8CBSE

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

🔑Concepts

•

Ecosystem Balance: An ecosystem is a self-sustaining unit where biotic (living) and abiotic (non-living) components interact. A change in one component, such as the removal of a predator, triggers a 'domino effect' throughout the food web.

•

Food Chains and Webs: Energy flows in a linear pathway called a food chain. Multiple interconnected food chains form a food web. The direction of energy flow is represented by arrows: Producers→Primary Consumers→Secondary Consumers\text{Producers} \rightarrow \text{Primary Consumers} \rightarrow \text{Secondary Consumers}.

•

The 10% Law: This rule states that only 10%10\% of the energy available at one trophic level is transferred to the next level. The remaining 90%90\% is lost as heat or used for metabolic processes.

•

Photosynthesis: The primary source of energy for most ecosystems. Green plants convert solar energy into chemical energy: 6CO2+6H2O→Sunlight/ChlorophyllC6H12O6+6O26CO_{2} + 6H_{2}O \xrightarrow{\text{Sunlight/Chlorophyll}} C_{6}H_{12}O_{6} + 6O_{2}

•

Consequences of Deforestation: Reducing forest cover leads to increased CO2CO_{2} levels, which causes Global Warming. It also disrupts the water cycle: ↓Trees→↓Transpiration→↓Rainfall\downarrow \text{Trees} \rightarrow \downarrow \text{Transpiration} \rightarrow \downarrow \text{Rainfall}.

•

Biological Magnification: The increase in concentration of harmful chemicals (like pesticides) as we move up the food chain. If a plant has 11 unit of toxin, a top predator may accumulate significantly higher concentrations.

📐Formulae

En+1=En×0.10E_{n+1} = E_{n} \times 0.10

6CO2+6H2O→C6H12O6+6O26CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}

Energy Loss=Total Energy−Energy Transferred\text{Energy Loss} = \text{Total Energy} - \text{Energy Transferred}

💡Examples

Problem 1:

In a food chain: Grass→Deer→Lion\text{Grass} \rightarrow \text{Deer} \rightarrow \text{Lion}, if the Grass produces 20,000 J20,000\text{ J} of energy, calculate the energy available to the Lion.

Solution:

  1. Energy at Producer level (Grass) = 20,000 J20,000\text{ J}.
  2. Energy at Primary Consumer level (Deer) = 10%10\% of 20,000 J20,000\text{ J} Edeer=10100×20,000=2,000 JE_{\text{deer}} = \frac{10}{100} \times 20,000 = 2,000\text{ J}
  3. Energy at Secondary Consumer level (Lion) = 10%10\% of 2,000 J2,000\text{ J} Elion=10100×2,000=200 JE_{\text{lion}} = \frac{10}{100} \times 2,000 = 200\text{ J}

Explanation:

According to Lindeman's 10% Law, only a small fraction of energy reaches higher trophic levels, which is why food chains rarely exceed 4-5 levels.

Problem 2:

A forest area was originally 850,000 hectares850,000\text{ hectares}. After a decade of industrialization, 123,450 hectares123,450\text{ hectares} were cleared. Calculate the remaining forest area using vertical subtraction.

Solution:

850000−123450726550\begin{array}{r} 850000 \\ - 123450 \\ \hline 726550 \end{array} Remaining area = 726,550 hectares726,550\text{ hectares}.

Explanation:

Significant reduction in forest area leads to habitat loss and an increase in atmospheric carbon dioxide, disrupting the natural harmony of the carbon cycle.

How Does One Change Lead to Another? Class 8 Notes & Examples