Answer: The offspring of sexually reproducing organisms are all genetically unique. Because of this, sexually reproducing organisms may have more successful survival of offspring in environments that change than asexually reproducing organisms, whose offspring are all genetically identical.
Natural selection can be
defined as the basic mechanisms of which goes along with migration, mutation
and genetic drift. Also, it is process in which an organism get adapted to its
environment by means of selectively reproducing changes in its genetic constitution.
Moving thing in and out requires surface area, many small cells have much more surface area for much less volume than one big cell so it is more efficient.