Why are cells united in tissues in a multicellular organism?

The organism of multicellular animals is a single whole. The cells that form it cannot live independently, since none of them is capable of performing all the functions inherent in a multicellular organism as a whole.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.