Symbiotic Relationships Across Diverse Phyla

All three groups have symbiotic species. Cnidarians establish mutualistic bonds with zooxanthellae to form coral reef ecosystems. Fungi form lichens with algae and mycorrhizae with the roots of vascular plants. Protozoa form vital mutualisms, such as ciliates or flagellates residing in the digestive tracts of ruminants and termites to break down complex cellulose. > Symbiosis is an ubiquitous ecological strategy found across primitive animals, fungi, and single-celled protozoans. Answer: (d).