What else can be the cause of variation?

Genetic variation exists because of changes to chromosomes or genes (DNA).

Mutations are random changes in the number of chromosomes (e.g. Down syndrome) or the structure of a gene (e.g. cystic fibrosis).

Independent assortment during meiosis increases variation because it results in genetically different gametes .

Explanation:

the cause of variation are

hope it helps.

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation