Organelles have their own genomes. when chloroplast dna is sequenced and compared to genomes from members of the cyanobacteria, the sequence is nested within cyanobacteria. this is strong evidence for the hypothesis that:

This is strong evidence for the hypothesis that the chroloplast originated ais a symbiotic cyanobacteriam that became permanentely  incorporated into its host.the complete genome sequence of cyanobacteria and of the higher plant arabidopsis thaliana leave no doubt tha chroloplast originated through endosymbiosis from a cyanobacteriam

Organelles have their own genomes. when chloroplast DNA is sequenced and compared to genomes from members of the cyanobacteria, the sequence is nested within cyanobacteria. this is strong evidence for the hypothesis that: 

The chloroplast originated as a symbiotic cyanobacterium that became permanently incorporated into its host.

It's either -limiting factors or -scarce resources but i'd go with my first answer since the food and water are abundant they really aren't scarce