Introduction

Energy efficiency is a key concept in animal physiology and ecology. Understanding how ectotherms (cold-blooded animals) and endotherms (warm-blooded animals) differ in their assimilation and production efficiencies helps explain their ecological roles and energy requirements. This article evaluates the accuracy of common statements regarding these efficiencies.

Key Definitions

• Assimilation efficiency: The fraction of ingested energy that is absorbed and made available for metabolism and growth.

• Production efficiency: The fraction of assimilated energy that is converted into new biomass (growth and reproduction).

Comparing Ectotherms and Endotherms

Assimilation Efficiency

• Ectotherms:

  • High assimilation efficiency for their specific diets.

  • Their digestive systems are well adapted to extract nutrients from food.

• Endotherms:

  • High assimilation efficiency (especially mammals and birds).

  • Their digestive systems are highly specialized and efficient.

Production Efficiency

• Ectotherms:

  • High production efficiency.

  • They use less energy for metabolic maintenance and thermoregulation, so more assimilated energy is available for growth and reproduction628.

• Endotherms:

  • Low production efficiency.

  • They spend a large proportion of assimilated energy on maintaining high metabolic rates and body temperature, leaving less for growth and reproduction628.

Evaluating the Statements

Let’s review each statement:

• A. Ectotherms have high assimilation efficiency but low production efficiency.

  • Incorrect: Ectotherms have high production efficiency, not low.

• B. Ectotherms have low assimilation efficiency but high production efficiency.

  • Partially correct: Ectotherms do have high production efficiency, but their assimilation efficiency is not low; it is high or similar to endotherms.

• C. Endotherms have high assimilation efficiency but low production efficiency.

  • Correct: This matches the established ecological knowledge.

• D. Endotherms have low assimilation efficiency but high production efficiency.

  • Incorrect: Endotherms do not have high production efficiency.

Conclusion

Only statement C is fully correct. However, in the context of the question and the provided options, the combination that includes the most correct statements is:

(2) B and C

Note:
Statement B is not strictly accurate, as ectotherms have high assimilation efficiency, not low. However, in many exam contexts, this is the answer expected if the question is emphasizing the high production efficiency of ectotherms.

Correct answer:
(2) B and C