Which sense enables animals to orient and navigate using Earth's magnetic field?

• A. Cryptochromes
• B. Magnetoreception
• C. Olfactory navigation
• D. Constant frequency

Answer: (B)

Magnetoreception is the sense that lets animals detect Earth's magnetic field and use it to orient and navigate. This ability helps migratory birds choose direction and timing, and sea turtles find their way to nesting beaches, among other examples. Some animals rely on magnetite-based receptors that sense field direction, while in others a radical-pair mechanism in light-sensitive proteins like cryptochromes may play a role. The question is about the actual sense, not the specific molecules or mechanisms behind it. The remaining options point to molecules involved in the mechanism (cryptochromes), a navigation method based on smell (olfactory navigation), or something unrelated (constant frequency).