This symbiotic relationship provides support for the theory of endosymbiosis, which states that a) animal-like cells evolved from ancestors that were photosynthetic. b) mitochondria and chloroplasts evolved from small prokaryotes living within larger cells. c) photosynthetic organisms, like today's land plants, evolved from photosynthetic bacteria. d) heterotrophic organisms could not have evolved before the evolution of photosynthetic organisms.