The technique used to measure the amount of light absorbed by a substance is: MCQ with Answer and Explanation

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.

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 epididymis is a coiled tube on the posterior surface of the testis where spermatozoa undergo maturation and are stored until ejaculation. Sperm acquire motility here. Seminal vesicles and prostate gland secrete seminal fluid. Vas deferens transports sperm from epididymis to ejaculatory duct. Testes produce sperm and testosterone. Sperm maturation includes gaining ability to fertilize.