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How Nature Works in Harmony - How do healthy ecosystems serve our farms?

Grade 8CBSE

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

🔑Concepts

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Healthy ecosystems provide essential services to agriculture through pollination. Over 75%75\% of the world's food crops depend at least in part on pollination by insects like bees, butterflies, and birds.

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Biological Pest Control: Ecosystems maintain a balance between pests and predators. For instance, birds and spiders act as natural predators for insects that might damage crops, reducing the need for chemical pesticides.

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Soil Fertility: Decomposers like fungi, bacteria, and earthworms break down organic matter into HumusHumus, enriching the soil with nutrients like Nitrogen (NN), Phosphorus (PP), and Potassium (KK).

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Nitrogen Fixation: Healthy soil contains bacteria such as RhizobiumRhizobium which convert atmospheric nitrogen (N2N_2) into usable nitrates (NO3−NO_3^-) for plants.

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Water Regulation and Purification: Natural vegetation and healthy soil act as sponges, absorbing rainwater and recharging groundwater levels, which prevents soil erosion and ensures a steady water supply for irrigation.

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The Carbon Cycle: Plants in a healthy ecosystem perform photosynthesis, absorbing CO2CO_2 and releasing O2O_2, which helps in maintaining the atmospheric balance and mitigating local climate changes.

📐Formulae

6CO2+6H2O→Sunlight/ChlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{Sunlight/Chlorophyll}} C_6H_{12}O_6 + 6O_2

Net Yield=Gross Yield−(Loss due to Pests+Loss due to Disease)\text{Net Yield} = \text{Gross Yield} - (\text{Loss due to Pests} + \text{Loss due to Disease})

N2 (Atmospheric)→Nitrogen Fixing BacteriaNitrogenous Compounds (e.g., NO3−)N_2 \text{ (Atmospheric)} \xrightarrow{\text{Nitrogen Fixing Bacteria}} \text{Nitrogenous Compounds (e.g., } NO_3^- \text{)}

Soil Porosity (%)=(1−Bulk DensityParticle Density)×100\text{Soil Porosity (\%)} = \left( 1 - \frac{\text{Bulk Density}}{\text{Particle Density}} \right) \times 100

💡Examples

Problem 1:

A farmer observes that without natural pollinators, his sunflower field produces 1200 kg1200\text{ kg} of seeds. With the introduction of a healthy bee population, the yield increases to 1800 kg1800\text{ kg}. Calculate the increase in yield and the percentage increase.

Solution:

Step 1: Calculate the increase in yield: 1800−1200600\begin{array}{r} 1800 \\ -1200 \\ \hline 600 \end{array} Increase =600 kg= 600\text{ kg}.

Step 2: Calculate percentage increase: Percentage Increase=6001200×100=50%\text{Percentage Increase} = \frac{600}{1200} \times 100 = 50\%

Explanation:

The presence of bees facilitates better cross-pollination, leading to a higher seed set and significantly increasing the total agricultural output.

Problem 2:

In a balanced ecosystem, a group of birds consumes approximately 50005000 harmful insects per day. If a farmer uses a pesticide that kills these birds, and the insect population grows by 1500015000 in a week, how many insects would the birds have prevented over that same week (77 days)?

Solution:

Step 1: Calculate insects consumed per week by birds: 5000×735000\begin{array}{r} 5000 \\ \times 7 \\ \hline 35000 \end{array} Insects prevented =35000= 35000.

Explanation:

Natural predators like birds provide 'ecosystem services' by controlling pest populations. Losing them forces the farmer to rely on expensive and potentially harmful chemical alternatives.