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Ecology and Conservation - Human Impact on Ecosystems

Grade 6IB

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

🔑Concepts

The Greenhouse Effect: Human activities like burning fossil fuels increase the concentration of greenhouse gases such as Carbon Dioxide (CO2CO_2) and Methane (CH4CH_4), which trap heat in the atmosphere.

Ocean Acidification: Increased atmospheric CO2CO_2 dissolves in oceans to form Carbonic Acid (H2CO3H_2CO_3), lowering the pHpH and harming marine organisms that rely on Calcium Carbonate (CaCO3CaCO_3) for shells.

Deforestation: Removing trees reduces the rate of photosynthesis, meaning less CO2CO_2 is removed from the atmosphere and less O2O_2 is produced, disrupting the global carbon cycle.

Eutrophication: Excess nutrients like Nitrates (NO3NO_3^-) and Phosphates (PO43PO_4^{3-}) from fertilizers run off into water bodies, causing algal blooms that deplete dissolved oxygen (O2O_2).

Biodiversity Loss: Human impact through habitat destruction and pollution leads to a decrease in species richness, making ecosystems less resilient to changes.

Conservation Strategies: Methods such as reforestation, creating protected areas, and reducing our carbon footprint to maintain the pHpH balance and stability of ecosystems.

📐Formulae

6CO2+6H2OlightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2

CO2+H2OH2CO3CO_2 + H_2O \rightarrow H_2CO_3

C6H12O6+6O26CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

pH=log[H+]pH = -\log[H^+]

💡Examples

Problem 1:

A forest area was measured to have a carbon absorption rate of 150 kg150\text{ kg} of CO2CO_2 per day. After a portion of the forest was cleared, the absorption rate dropped to 90 kg90\text{ kg} per day. Calculate the percentage decrease in CO2CO_2 absorption.

Solution:

Percentage Decrease=15090150×100=40%\text{Percentage Decrease} = \frac{150 - 90}{150} \times 100 = 40\%

Explanation:

The reduction in the number of trees decreases the total amount of CO2CO_2 captured through photosynthesis. The 40%40\% decrease shows a significant loss in the ecosystem's ability to mitigate the greenhouse effect.

Problem 2:

Identify the gas responsible for ocean acidification and explain its chemical transition when it hits the water.

Solution:

The gas is Carbon Dioxide (CO2CO_2). When it dissolves, it reacts as follows: CO2+H2OH2CO3CO_2 + H_2O \rightarrow H_2CO_3 (Carbonic Acid).

Explanation:

Carbonic acid dissociates into hydrogen ions, which lowers the pHpH of the water. This makes the environment more acidic, which dissolves the CaCO3CaCO_3 (Calcium Carbonate) in the shells of shellfish and coral reefs.