Are there any organisms that do not
have tissue structures?
yes or no?

Yes , there any organisms that do not  have tissue structures.

Explanation:

Unicellular organisms lacks tissue structures because they are made up of only one cell (i.e Amoeba, Paramecium, diatoms and bacteria). They carry out various life processes like metabolism,respiration etc., within the single cell. Hence, they lack the tissue structures.

Even in lower order of animals, tissue structures are absent,(nervous system and sense organs ). Here the cell forms groups but fails to perform definite function. Since, tissue are nothing else but a group of cells that performs together.  

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