How does the example of hatena and the alga represent an emergent explanation of life?

Hatena and algae have a symbiotic relationship. Hatena normally fulfills its nutritional needs by ingesting organic matter. However, when it behaves as a predator and ingests alga, it switches from fulfilling its nutritional needs to one that uses photosynthesis. Hatena arenicola is a protist with one rounded cell having two flagella for locomotion. It feeds on algae using a complex feeding tube when it mains an self-determining life. The feeding tube is substituted by an end symbiotic alga. The algal endosymbiont is a green alga from the genus nephroselmis. The endosymbiont not only deeds as feeding apparatus but also as an eye spot by which it probably aids the protist for guiding actions in the direction of light photo-taxis.