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Continuity and change - Sustainability and change

Grade 11IBBiology

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

🔑Concepts

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Sustainability in ecosystems refers to the ability of biological systems to remain diverse and productive indefinitely. This relies on the continuous supply of energy (usually from sunlight) and the efficient recycling of nutrients like carbon and nitrogen.

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Energy flow through an ecosystem is unidirectional. Approximately 90%90\% of energy is lost as heat due to respiration and metabolic processes at each trophic level, limiting the number of levels in a food chain.

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Net Primary Productivity (NPPNPP) is the rate at which producers store energy as biomass, after subtracting the energy used for cellular respiration (RR). It represents the energy available to consumers.

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Ecological succession describes the process of change in the species structure of an ecological community over time. Primary succession starts on bare inorganic surfaces, while secondary succession occurs in areas where soil already exists but the community was disturbed.

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Tipping points are critical thresholds in ecological systems where a small change can lead to a drastic and often irreversible shift in the state of the ecosystem (e.g., the melting of permafrost releasing CH4CH_4).

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Climate change is driven by the enhanced greenhouse effect. Anthropogenic activities increase the concentration of greenhouse gases such as CO2CO_2, CH4CH_4, and N2ON_2O, which trap long-wave infrared radiation in the atmosphere.

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Keystone species play a disproportionately large role in maintaining the structure and sustainability of an ecosystem. Their removal often leads to a trophic cascade and ecosystem collapse.

📐Formulae

NPP=GPP−RNPP = GPP - R

Efficiency=Energy at higher trophic levelEnergy at lower trophic level×100Efficiency = \frac{Energy \text{ at higher trophic level}}{Energy \text{ at lower trophic level}} \times 100

ΔN=(B+I)−(D+E)\Delta N = (B + I) - (D + E)

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

💡Examples

Problem 1:

In a temperate forest, the Gross Primary Productivity (GPPGPP) is measured at 35,000 kJ m−2y−135,000 \text{ kJ } m^{-2} y^{-1}. If the autotrophs utilize 18,500 kJ m−2y−118,500 \text{ kJ } m^{-2} y^{-1} for their own cellular respiration (RR), calculate the Net Primary Productivity (NPPNPP).

Solution:

NPP=35,000−18,500NPP = 35,000 - 18,500 NPP=16,500 kJ m−2y−1NPP = 16,500 \text{ kJ } m^{-2} y^{-1}

Explanation:

Net Primary Productivity is calculated by subtracting the energy used for respiration from the total energy captured during photosynthesis (GPP).

Problem 2:

A food chain consists of Grass →\rightarrow Grasshopper →\rightarrow Frog. If the Grass level contains 25,000 J25,000 \text{ J} of energy and the Grasshopper level contains 2,250 J2,250 \text{ J}, calculate the percentage efficiency of energy transfer.

Solution:

Efficiency=2,25025,000×100Efficiency = \frac{2,250}{25,000} \times 100 Efficiency=0.09×100=9%Efficiency = 0.09 \times 100 = 9\%

Explanation:

The efficiency is the ratio of energy available at the consumer level to the energy available at the producer level, expressed as a percentage.

Problem 3:

Calculate the population change in a bird colony where there were 150150 births, 4545 deaths, 1212 immigrants, and 88 emigrants during a single year.

Solution:

ΔN=(150+12)−(45+8)\Delta N = (150 + 12) - (45 + 8) ΔN=162−53\Delta N = 162 - 53 ΔN=109\Delta N = 109

Explanation:

The net change in population size is determined by adding births and immigration (inputs) and subtracting deaths and emigration (outputs).