The phylogenetic tree is a diagram portraying multiple branches to show the relationships between organisms of the same species or other species, all of which are dependent on the differences and similarities in their phenotypical or inherited traits. It is used to determine how and when a species developed complex characteristics that differentiate them from their simple unicellular ancestors.
To use the phylogenetic tree to prove the validity of statements about secondary endosymbiosis, the statements must (a) indicate a relationship between the original organism and the new organism, (b) support that intra- and interspecies fusion can result in the formation of new species.
Unlike in primary endosymbiosis, secondary endosymbiosis occurs when a living unicellular organism absorbs another unicellular cell. The main difference is that secondary endosymbiosis occurs in a cell that has undergone endosymbiosis primarily.
This has led to the formation of new species and naturally-occurring variants of a species.