Energy metabolism — Identify the single false statement (others are true with proper wording and scope).

Difficulty: Medium

The energy that powers most living systems on Earth ultimately originates from the sun
All animals ultimately depend on primary producers (such as plants or algae) for chemical energy flow in their food webs
Plants provide the water and carbon dioxide that animals need to carry out respiration
Most eukaryotic cells generate ATP via aerobic respiration in mitochondria when oxygen is available
Decomposers recycle nutrients but do not create new energy; energy flows and is lost as heat

Correct Answer: Plants provide the water and carbon dioxide that animals need to carry out respiration

Explanation:

Introduction / Context:
This concept question integrates ecology and physiology. It asks you to distinguish accurate generalizations about energy flow and respiration from a deliberately incorrect statement about the gases used by animals during cellular respiration.

Given Data / Assumptions:

Energy for nearly all ecosystems is solar in origin, captured by photosynthesis.
Animals are heterotrophs; their energy comes from organic matter originating from primary producers (plants, algae, some bacteria).
Aerobic respiration uses O2 as the terminal electron acceptor and produces CO2 and water as products.

Concept / Approach:
Evaluate each statement using core principles. The false statement should attribute the wrong gases to animal respiration requirements. Animals require O2, not CO2, to carry out aerobic respiration; they release CO2. The other statements are broadly true with proper scope qualifiers (for example, “most” or “ultimately”).

Step-by-Step Solution:

Check (a): Primary energy source for Earth’s biosphere is the sun → broadly true.Check (b): Food chains originate with primary producers → true as a general rule.Check (c): Claims animals need CO2 for respiration → false; animals need O2 and produce CO2.Check (d): Aerobic respiration in eukaryotes occurs in mitochondria → true when O2 is present.Check (e): Consistent with thermodynamics in ecosystems → true.

Verification / Alternative check:
Basic physiology confirms that hemoglobin transports O2 to tissues; mitochondria consume O2 and generate CO2 via the TCA cycle and pyruvate oxidation.

Why Other Options Are Wrong:

a) Correct—photosynthesis captures solar energy that fuels ecosystems.b) Correct—animals depend on producer biomass directly or indirectly.d) Correct—many eukaryotes respire aerobically when oxygen is available.e) Correct—decomposers recycle matter; energy is dissipated as heat.

Common Pitfalls:
Confusing animal respiration with plant gas exchange; both use O2 in mitochondria, but plants also produce O2 in photosynthesis.

Final Answer:
Plants do not provide CO2 for animal respiration; animals require O2 and produce CO2, so option (c) is false.

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Energy metabolism — Identify the single false statement (others are true with proper wording and scope).

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