How to "describe the significance and formation of colonial organisms" to make a timeline about the earths evolution for a Biology assignment?

Colonial organisms (organisms that form
colonies) are hypothesized to have led to the formation of multicellular organisms, according to
the colonial theory. All the plants, animals and higher life forms are multicellular (i.e.
consist of more than one cell) in nature. 

Identical organisms group together
to form colonies for mutual benefits (security, food access, etc.), much like human beings.
Haeckel, in 1874, proposed the colonial theory, according to which multicellular organisms
developed as a result of colonial organisms forming colonies. For example, Salpingoeca
rosetta (a bacterial predator) form rosette-shaped colonies and this enables them to
capture bacteria more efficiently. It is hypothesized that organisms (such as flagellated
protist) form colonies and by selective reproduction of individual organisms evolve into a
tissue (or a multicellular organism). Colonial organisms are supposed to have developed around
1.5 billion years ago.