Many protista contain chloroplasts.
There is lots of evidence for a common ancestor but I suggest you look at wikipedia's evidence for common descent or Talk origins 29 evidence for evolution.
There has been no evidence of such an ancestor.
The kingdom Protista (also known as Protoctista) includes organisms such as Protozoa, Algae and Fungus.
Mollusks and segmented worms have a one-way digestive system, a separate mouth and anus, and their larvae are very similar. This is the best evidence that they have a common ancestor.
Amoeba proteus, the common amoeba, is currently classified in Kingdom Amoebozoa. Older sources may list amoebae under the now-defunct Kingdom Protista or (in really old books) Kingdom Animalia. The change is because of the current trend to define taxonomic groups on evolutionary kinship.
The Kingdom Protista is polyphyletic including members derived from 2 or more ancestral forms not common to all members & thus do not reflect phylogeny. Among several alternate classifications, a popular 8-kingdom system recognizes 3 protist kingdoms (Archaezoa, Protista & Chromista) in place of the single kingdom Protista. However, the less inclusive version of the Kingdom Protista is still polyphyletic. Using nucleic acid sequencing, systematics has begun sorting out monophyletic groups.
We all current life has a single common ancestor.
Physiological similarities suggest the species evolved from the same ancestor.
Evidence that tells that, through the structures of two organisms, can be compared that we have a common ancestor and have evolved from them.
descended from a common ancestor
Homologous structures indicate a common ancestor
Rape