Thermodynamics of development: When a single fertilized egg (zygote) organizes itself into a multicellular embryo with specialized tissues, what happens to the entropy (degree of disorder) of this living system?

Introduction / Context:
Biology often invokes thermodynamics to explain how living systems organize. A classic example is embryogenesis, where a single fertilized cell divides and differentiates to form a complex embryo. The key question is how the order within the living system changes during this process.

Given Data / Assumptions:

• The system being discussed is the living organism (zygote to embryo), not the entire universe.
• Cell division and differentiation produce ordered tissues and organs.
• Organism exchanges energy and matter with its surroundings (open system).

Concept / Approach:
Entropy measures disorder. When biological structures become more organized (cells adopt specific fates, tissues form patterns), the internal entropy of the organism decreases. The second law of thermodynamics is not violated because the organism exports entropy (for example, as heat and waste) to the environment, increasing the surroundings’ entropy more than enough to compensate.

Step-by-Step Solution:

Verification / Alternative check:
Textbook explanations of morphogenesis and self-organization consistently describe a decrease in system entropy with energy dissipation into the environment.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing the organism (open system) with the universe (isolated). The second law applies to the combined system plus surroundings.

Final Answer:
Decreases.