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Human Influences on Ecosystems - Conservation

Grade 11IGCSEBiology

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

🔑Concepts

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Sustainable development is defined as providing for the needs of an increasing human population without harming the environment or compromising the ability of future generations to meet their needs.

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Sustainable resources include those that are produced as rapidly as they are removed from the environment, such as timber from managed forests or fish stocks managed through quotas.

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Conservation of species is essential to maintain biodiversity, protect food chains, and preserve potential medicinal resources. This is achieved through captive breeding programs and seed banks.

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Habitat conservation aims to protect the entire ecosystem by establishing national parks and reserves, ensuring that the cycling of nutrients (e.g., N2N_2 and CO2CO_2) remains stable.

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Recycling reduces the consumption of raw materials and energy. For instance, recycling aluminum (AlAl) uses only 5%5\% of the energy required to extract it from bauxite ore.

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Sewage treatment involves removing organic matter and pathogens from water. Aerobic bacteria break down organic compounds into CO2CO_2, H2OH_2O, and mineral ions, preventing high Biochemical Oxygen Demand (BODBOD) and eutrophication.

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Reasons for conservation include: moral/ethical responsibility, economic benefits (e.g., ecotourism), maintaining genetic diversity, and preserving ecosystem services like pollination and climate regulation.

📐Formulae

Efficiency of Energy Transfer=(Energy in tissuesEnergy in food eaten)×100\text{Efficiency of Energy Transfer} = \left( \frac{\text{Energy in tissues}}{\text{Energy in food eaten}} \right) \times 100

Aerobic Respiration by Decomposers:C6H12O6+6O2→6CO2+6H2O\text{Aerobic Respiration by Decomposers:} \quad C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O

Simpson’s Index of Diversity (Index D)=1−∑n(n−1)N(N−1)\text{Simpson's Index of Diversity (Index } D) = 1 - \frac{\sum n(n-1)}{N(N-1)}

💡Examples

Problem 1:

A forest management team monitors a population of trees. If the rate of extraction is RR and the rate of regrowth is GG, define the condition for the resource to be sustainable.

Solution:

G≥RG \ge R

Explanation:

For a resource to be sustainable, the rate of regrowth (GG) must be equal to or greater than the rate of harvesting/extraction (RR) to ensure the stock does not deplete over time.

Problem 2:

Explain the role of bacteria in the nitrogen cycle during sewage treatment to prevent the accumulation of NO3−NO_3^- in water bodies.

Solution:

Denitrifying bacteria convert NO3−NO_3^- into N2N_2 gas.

Explanation:

In sewage treatment, after organic matter is broken down into nitrates (NO3−NO_3^-), denitrifying bacteria can be used in anaerobic conditions to convert these nitrates into harmless nitrogen gas (N2N_2), which is released into the atmosphere, preventing eutrophication.

Problem 3:

Calculate the percentage increase in recycling efficiency if the energy required for new plastic production is 100 units100 \text{ units} and recycled plastic requires 20 units20 \text{ units}.

Solution:

Energy Saved=100−20100×100=80%\text{Energy Saved} = \frac{100 - 20}{100} \times 100 = 80\%

Explanation:

Recycling saves 80%80\% of the energy compared to producing new plastic from crude oil, significantly reducing CO2CO_2 emissions and environmental impact.

Conservation - Revision Notes & Key Diagrams | IGCSE Grade 11 Biology