An ecologist examining the leaves of a diseased plant wonders if the fungus found on its roots is the pathogenic organism. Which step would be least necessary in order for the scientist to confirm that the fungus is responsible for the disease

See the answer below

Explanation:

It seems like you forgot to include the available options in order to answer the question.

However, according to plant pathologists, in order to establish that a particular organism is responsible for a certain observable disease, certain conditions have to be fulfilled. These conditions include:

Any other condition that is short of the above-listed conditions can be considered to be least necessary in order for scientists to confirm if an organism is responsible for a particular disease.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.