Although all mammals have some common characters, but they shows conspicuous differences due to

The correct answer is: Divergence

Divergence.
Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species. Usually, it is a result of diffusion of the same species to different and isolated environments which blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics through genetic drift and natural selection

Primarily diffusion is the basis of molecular division which can be seen in some higher-level characters of the structure and function that are readily observable in organisms. For example, the vertebrate limb is one example of divergent evolution. The limb in many different species has a common origin, but has diverged somewhat in overall structure and function

Homologous Organs The organs which have the same fundamental structure but are different in functions are called homologous orangs. These organs follows the same basic plan of organization during development. But in adult condition, these organs are modified to perform different function as an adaptation to the different environment. Homologous organs are the resultant of divergent evolution

Implants homologous organs may be a those of Bougainvillea or a tendril of Cucurbita, both arising in the axillary position