Identify the correct statement about plant diseases: MCQ with Answer and Explanation

Explanation:
Biological nitrogen fixation, performed by bacteria (Rhizobium, Azotobacter) and cyanobacteria, reduces N₂ to NH₃. Nitrification oxidizes ammonia to nitrates, denitrification returns N₂, ammonification releases ammonia from organic matter.

Explanation:
The cerebellum, meaning 'little brain', is a highly folded structure located at the posterior base of the skull, beneath the occipital lobes of the cerebrum and behind the brainstem. While it does not initiate movement, its primary functions are to coordinate voluntary motor movements, ensure muscle synergy, maintain posture, and regulate balance and equilibrium. It receives sensory input from the spinal cord, vestibular system, and cerebral cortex, and fine-tunes motor output to ensure smooth, accurate movements. Damage to the cerebellum results in ataxia (clumsy, uncoordinated movements).

Explanation:
Rhodopsin (visual purple) is a photopigment in rod cells consisting of opsin and retinal (from vitamin A). It bleaches upon absorbing light, initiating signal transduction for vision in low light. Cone cells contain iodopsin for color vision. Melanin is skin pigment, hemoglobin carries oxygen.