Why reproduction is necessary?

Why reproduction is necessary? Is it essential for survival? If a living organism does not reproduce, in which category it will belong, living or non-living? How is sexual reproduction different from asexual reproduction ?

Reproduction is required for the perpetuation of a population. It is not necessary for the survival of living organisms. Many organisms, e.g., Mules, sterile worker bees, infertile human couples are not able to reproduce, while they have all other defining properties of life, so they can be called as living.
Sexual reproduction involves the formation and fusion of two kinds of gametes to produce an offspring. In asexual reproduction, new individuals can arise by the specialised parts of body or without the fusion of gametes.