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Ecology and Earth Science - Biotic and Abiotic Factors

Grade 7IB

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

🔑Concepts

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Biotic factors are the living components of an ecosystem, including producers (plants), consumers (animals), and decomposers (bacteria and fungi).

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Abiotic factors are the non-living physical and chemical elements in the environment, such as sunlight, temperature, soil pHpH, and moisture levels (H2OH_2O).

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The ecosystem is a complex system where biotic and abiotic factors interact; for example, plants (biotic) require CO2CO_2 and sunlight (abiotic) for photosynthesis.

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Limiting factors are abiotic or biotic variables that restrict the growth, abundance, or distribution of an individual or a population within an ecosystem.

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Levels of biological organization range from the individual organism to the biosphere: Organism→Population→Community→Ecosystem→Biosphere\text{Organism} \rightarrow \text{Population} \rightarrow \text{Community} \rightarrow \text{Ecosystem} \rightarrow \text{Biosphere}.

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Photosynthesis is a primary interaction where biotic organisms convert abiotic substances into chemical energy: 6CO2+6H2O+light energy→C6H12O6+6O26CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2.

📐Formulae

6CO2+6H2O→lightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2

Population Density=NA\text{Population Density} = \frac{N}{A}

C6H12O6+6O2→6CO2+6H2O+ATP (Energy)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP (Energy)}

T(K)=T(∘C)+273.15T(K) = T(^\circ C) + 273.15

💡Examples

Problem 1:

Identify the biotic and abiotic factors in a desert ecosystem where a cactus grows in sandy soil under high intensity solar radiation and temperatures reaching 45∘C45^\circ C.

Solution:

Biotic factors: Cactus. Abiotic factors: Sandy soil, solar radiation, and temperature (45∘C45^\circ C).

Explanation:

Biotic factors must be living organisms, while abiotic factors are the physical and chemical conditions of the environment.

Problem 2:

A scientist measures the population of 5050 deer in a forest area of 10km210 km^2. Calculate the population density using the formula Density=NA\text{Density} = \frac{N}{A}.

Solution:

Density=50 deer10km2=5 deer/km2\text{Density} = \frac{50 \text{ deer}}{10 km^2} = 5 \text{ deer/km}^2

Explanation:

Population density is a measure of the number of biotic individuals per unit of abiotic space (area).

Problem 3:

How does the abiotic factor of pHpH affect biotic life in an aquatic ecosystem if the pHpH drops from 7.07.0 to 4.04.0 due to acid rain (H2SO4H_2SO_4)?

Solution:

The drop in pHpH (increase in acidity) can lead to the death of sensitive fish species and disrupt the reproductive cycles of amphibians.

Explanation:

Organisms have a specific range of tolerance for abiotic factors; moving outside this range (pH<5.0pH < 5.0) causes physiological stress or death.