U1: Ecosystem Dynamics, Energy Flow, and Thermodynamic Laws

Which sequence correctly arranges the levels of ecological organization from the most specific unit to the most inclusive?

• Organism → Population → Community → Ecosystem → Biosphere
• Population → Organism → Community → Ecosystem → Biosphere
• Organism → Community → Population → Biosphere → Ecosystem
• Ecosystem → Biosphere → Community → Population → Organism

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GSE SEV1b

In a temperate forest ecosystem, producers store 80,000 kJ of energy through photosynthesis. Applying the 10% Rule, how much energy is available to tertiary consumers?

• 8,000 kJ
• 800 kJ
• 80 kJ
• 8 kJ

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GSE SEV1a

A student claims that when an herbivore eats a plant, 90% of the plant's energy is completely destroyed. How should this claim be evaluated using thermodynamic laws?

• The claim is accurate because energy decreases significantly across trophic levels.
• The claim is inaccurate because energy is conserved (First Law) and dissipated as metabolic heat (Second Law).
• The claim is accurate because the Second Law states that energy disappears during metabolic work.
• The claim is inaccurate because 100% of energy is transferred without loss to the consumer.

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GSE SEV1a

A severe drought causes wetland water levels to drop, increasing temperature and reducing dissolved oxygen. How do these changes affect the biological community?

• Abiotic stress reduces producer photosynthesis and fish survival across trophic levels.
• Biotic organisms increase oxygen production to offset the environmental stress.
• Biotic components transform into abiotic components to maintain stability.
• Abiotic changes impact decomposers while primary consumers remain unaffected.

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SEV1b

Which group of organisms occupies the first trophic level in an ecosystem?

• Autotrophs
• Herbivores
• Primary Consumers
• Apex Predators

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SEV1a

In a marine coastal food web, sea otters feed on sea urchins, which feed on kelp. If a disease eliminates sea otters, what immediate ecosystem shift occurs?

• Kelp density increases due to reduced predation pressure.
• Sea urchin populations expand rapidly, leading to kelp depletion.
• Primary consumers starve due to lack of available producers.
• Decomposer populations decline due to lower organic waste output.

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SEV1a

In a terrestrial food web consisting of grass, grasshoppers, frogs, and snakes, a disease drastically reduces the frog population. What immediate response is predicted?

• Grasshopper populations increase while snake populations decline.
• Grass populations decline while snake populations increase.
• Grasshopper and snake populations both increase exponentially.
• Grasshopper populations decrease due to increased snake predation.

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SEV1a

According to the First Law of Thermodynamics, how does energy move through biological systems?

• Energy is synthesized by producers and destroyed by consumers.
• Energy transforms between radiant and chemical forms while total energy is conserved.
• Energy accumulates progressively at higher trophic levels.
• Energy dissipates completely during cellular respiration without conversion.

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GSE SEV1a

Why is only approximately 10% of energy transferred from one trophic level to the next higher level?

• Most energy is expended in metabolic respiration and lost as thermal energy.
• Decomposers absorb 90% of energy before consumers can ingest it.
• Higher level consumers require less overall chemical energy to survive.
• Primary producers reflect 90% of consumed energy back to solar radiation.

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GSE SEV1a

A grassland receives 500,000 kJ of solar radiation. Primary producers assimilate 1% into net primary productivity (5,000 kJ). How much energy is stored in secondary consumer biomass?

• 500 kJ
• 50 kJ
• 5 kJ
• 50,000 kJ

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GSE SEV1a