Sec 1 - Integrated Sciences
Unit 2: Terrestrial Ecosystems and Earth Resources
Integrated Sciences: Biotic & Abiotic Interactions, Climate Determinants, and Major Biomes
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A terrestrial ecosystem is an intricate living network where biological communities (biotic factors) interact dynamically with their physical and chemical environment (abiotic factors). In this modern integrated curriculum, we bridge biology, chemistry, and physics to examine how solar energy and climatic gradients dictate life on land. Abiotic variables—such as temperature ranges, annual precipitation, soil texture, and sunlight intensity—act as primary limiting factors, determining the global distribution of major terrestrial biomes ranging from dense tropical rainforests to arid desert ecosystems.
1. Biotic & Abiotic Components
Living and non-living interactions:
- Biotic Factors:
• Producers (Autotrophs): Photosynthetic plants fixing solar energy into chemical bonds.
• Consumers (Heterotrophs): Herbivores, carnivores, and omnivores.
• Decomposers: Fungi and bacteria breaking down organic detritus to replenish soil nutrients. - Abiotic Factors: Sunlight, ambient temperature, relative humidity, atmospheric gases, and soil mineral composition.
2. Climatic Regimes & Major Biomes
Precipitation and thermal thresholds:
- Annual Precipitation: The single most decisive factor distinguishing rainforests (>2000 mm), grasslands (250-750 mm), and arid deserts (<250 mm).
- Solar Radiation & Latitude: Direct equatorial insolation drives high primary productivity, whereas polar tilt reduces available radiant energy.
- Carrying Capacity (K): The maximum population size of a species that an environment can sustainably support without habitat degradation.
Analytical Investigation:
Analytical Question: Why are saprophytic decomposers vital for maintaining ecological balance in terrestrial biomes?
Scientific Explanation: Without decomposers, essential macro-elements (nitrogen, phosphorus, carbon) would remain permanently locked in organic carcasses. Decomposers mineralize organic matter, returning soluble ions to the soil solution for root absorption.
Scientific Explanation: Without decomposers, essential macro-elements (nitrogen, phosphorus, carbon) would remain permanently locked in organic carcasses. Decomposers mineralize organic matter, returning soluble ions to the soil solution for root absorption.
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terrestrial ecosystem
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نظام بيئي أرضي
📖 Def: a community of organisms interacting with abiotic factors on land
biotic factors
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عوامل حيوية
📖 Def: the living components of an ecosystem: producers, consumers, and decomposers
abiotic factors
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عوامل غير حيوية
📖 Def: non-living physical and chemical elements: light, temperature, moisture, soil
biome
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منطقة أحيائية كبرى
📖 Def: a vast regional ecosystem defined by characteristic climate, vegetation, and fauna
carrying capacity
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القدرة الاستيعابية للبيئة
📖 Def: maximum sustainable population size supported by available resources
precipitation
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الهطول المطري
📖 Def: rain, snow, sleet, or hail falling to the ground
autotroph
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كائن ذاتي التغذية
📖 Def: an organism capable of synthesizing its own food from inorganic substances
limiting factor
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عامل بيئي محدد
📖 Def: an environmental condition that restricts the growth, abundance, or distribution of organisms
Click on an option to check your answer and view the detailed explanation:
1
Which of the following represents an autotrophic producer in a terrestrial ecosystem?
2
The primary abiotic limiting factor differentiating deserts from tropical rainforests is:
3
Decomposers (bacteria and fungi) are essential in soil dynamics because they:
4
The ultimate source of energy fueling biological activity across terrestrial biomes is:
5
A regional geographical zone characterized by shared climate patterns and dominant flora is called a:
6
The symbiotic association between Rhizobium bacteria and legume root nodules represents:
7
All of the following are hallmark characteristics of arid desert biomes EXCEPT:
8
The carrying capacity (K) of an ecosystem refers to:
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