Experiments conducted with germ-free animals have led to what conclusion?

• A. Germ-free animals have increased nutrient absorption compared to conventional animals.
• B. Germ-free animals are more resistant to infectious diseases.
• C. Normal microbiota are essential for proper development of the immune system.
• D. The absence of microbiota has no significant effect on animal physiology.

Answer: (C)

Verified step by step guidance

1. Understand the concept of germ-free animals: these are animals raised in a sterile environment without any microorganisms living in or on them.
2. Recognize that germ-free animals are used to study the role of normal microbiota by comparing their physiology and immune function to that of conventional animals with normal microbiota.
3. Review experimental observations showing that germ-free animals often have underdeveloped immune systems, indicating that normal microbiota play a crucial role in immune system development.
4. Analyze why other options are less accurate: for example, germ-free animals typically have decreased nutrient absorption and are often more susceptible, not more resistant, to infections.
5. Conclude that the key finding from germ-free animal studies is that normal microbiota are essential for proper development of the immune system.