Question

How asexual reproduction enables the organism survive during unfavourable conditions.

Answer 1

Usually as far as I know, sexual reproduction enables organism to tide over unfavourable condition. Many organisms that reproduce both sexually and asexually take over to sexual reproduction justbefore onset of unfavourable conditions.
Speaking about asexual reproduction, it doesn't produce variations that sexual reproduction does so as to increase survival advantage but it may have population advantage as organism can produced numerable offsprings within a short period of time unlike sexual reproduction.
Moreover if suppose an organism mutates and such a variation is created that can survive the given unfavourable condition, it can divide rapidly and produce organisms similar to itself thus increasing survival and population advantage.