Q. Which of the following have species that can establish symbiotic relationship with other organisms?
1. Cnidarians
2. Fungi
3. Protozoa
Select the correct answer using the code given below.

[A] 1 and 2 only

[B] 2 and 3 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: D
Notes:

Why this question: Important static topic 

Ans) d 

Exp) Option d is correct. 

Some organisms live together and share both shelter and nutrients. This relationship is called symbiosis. 

Statement 1 is correct. Cnidaria is an invertebrate phylum which often involves in a symbiotic relation with the unicellular dinoflagellate algae, calledzooxanthellae. 

Statement 2 is correct. Certain fungi live inside the roots of plants. The plants provide nutrients to the fungus and, in return, the fungus provides water and certain nutrients. Fungi also lives in a symbiotic relation with algae as a lichen. 

Statement 3 is correct. Protozoa also forms symbiotic relations with other organisms. Symbiosis in protozoa mostly represents: 

  •  a close mutualistic association between a protozoan and unicellular symbiont (like bacteria, cyanobacteria or/and unicellular algae) or  
  • protozoans and a multicellular organism (ruminants, lower termites, wood-eating cockroaches, plants) 

Source) NCERT class-7 PAGE-7 

https://www.biology-today.com/general-zoology/symbiotic-relationship-of-protozoans/ 

https://cals.arizona.edu/azaqua/algaeclass/symbios.htm#:~:text=The%20symbiotic%20association%20between%20the%20invertebrate%20phylum%20Cnidaria,is%20between%20zooxanthellae%20and%20hermatypic%2C%20or%20reef-forming%2C%20corals 

Subject) Environment