Mitosis and Meiosis
Mitosis is the process of somati cell division , its main functions are regeneration and growth.
Meiosis is the process of germline cell division, it produces genetic variation in the offspring.
Mitosis best suits the second scenario, where te skateboarder would need ra process of regeneration of the tissues of their knee; while meiosis best suits the first scenario, where genetic variation is needed in order to adapt and survive to a new environment.