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Biology - Habitat Destruction

Grade 9IGCSE

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

🔑Concepts

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Habitat destruction is the process by which a natural habitat becomes incapable of supporting its native species, primarily due to human activities such as agriculture, urban development, and mining.

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Deforestation involves the clearing of forests, leading to a reduction in biodiversity and the loss of habitats for millions of species. It disrupts the balance of atmospheric gases by decreasing the rate of photosynthesis (6CO2+6H2O→C6H12O6+6O26CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}).

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Leaching: When trees are removed, nutrients such as nitrates (NO3−NO_{3}^{-}) and phosphates (PO43−PO_{4}^{3-}) are washed out of the soil by rain into water bodies, potentially leading to eutrophication.

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Soil Erosion: Without tree roots to stabilize the soil and the canopy to break the impact of rain, the topsoil is easily washed away, making the land infertile.

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Disturbance of the Water Cycle: Trees release water vapor into the atmosphere through transpiration. Deforestation leads to drier climates and reduced rainfall in the local area.

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Imbalance of Atmospheric Gases: Trees act as 'carbon sinks'. Their removal increases the concentration of CO2CO_{2} in the atmosphere, contributing to the enhanced greenhouse effect and global warming (+ΔT+ \Delta T).

📐Formulae

6CO2+6H2O→light, chlorophyllC6H12O6+6O26CO_{2} + 6H_{2}O \xrightarrow{\text{light, chlorophyll}} C_{6}H_{12}O_{6} + 6O_{2}

Percentage Loss=Initial Area−Final AreaInitial Area×100\text{Percentage Loss} = \frac{\text{Initial Area} - \text{Final Area}}{\text{Initial Area}} \times 100

D=1−(∑n(n−1)N(N−1))D = 1 - \left( \frac{\sum n(n-1)}{N(N-1)} \right)

💡Examples

Problem 1:

A forest area covers 8000 km28000 \text{ km}^{2}. Due to logging for timber and agriculture, the area is reduced to 5200 km25200 \text{ km}^{2}. Calculate the percentage of the habitat that has been destroyed.

Solution:

8000−52002800\begin{array}{r} 8000 \\ - 5200 \\ \hline 2800 \end{array} Percentage Decrease=28008000×100\text{Percentage Decrease} = \frac{2800}{8000} \times 100 Percentage Decrease=0.35×100=35%\text{Percentage Decrease} = 0.35 \times 100 = 35\%

Explanation:

First, find the total area lost by subtracting the final area from the initial area. Then, divide the loss by the initial total area and multiply by 100 to get the percentage.

Problem 2:

Explain how the removal of trees affects the concentration of CO2CO_{2} in the atmosphere using the concept of carbon sinks.

Solution:

Net CO2 change=Emissions−Absorption\text{Net } CO_{2} \text{ change} = \text{Emissions} - \text{Absorption}

Explanation:

Trees are carbon sinks because they absorb CO2CO_{2} for photosynthesis. When trees are cut down, less CO2CO_{2} is removed from the atmosphere. Additionally, if the trees are burned, the stored carbon is released back as CO2CO_{2}, further increasing the atmospheric concentration and contributing to the greenhouse effect.