Meiosis involves a diploid cell dividing into two haploid cells. This is what happens when sperm is made in the testes and eggs made in the ovaries. On the other hand mitosis is 'normal cell division', the cell makes an exact copy (clone) of the full DNA (2n).

The skeleton gives our vital organs protection and also gives us stability (without we'd be a pile of cells with no clear structure!). The skeleton helps during physical activity too.