Which of the following statements is/are incorrect? (I) Mimicry is the ability of an organism to blend with background. (II) Camouflage allows animals to remain unnoticed from a distance. (III) The longest distance travelled by an animal is that of sea bird Arctic tern. (IV) A locust shows periodic migration.

Statement I is incorrect - mimicry is resembling another organism or object for protection, not blending with background (that's camouflage). Statement II (camouflage allows animals to remain unnoticed from distance) is correct. Statement III (Arctic tern's longest migration) is correct. Statement IV (locusts' periodic migration) is correct.