Describe the levels of organization in a tree

The tree represent an organ system level of organisation.

The biological level of organisation can be defined as the structural organisation in the body of the organism. The cell is the basic unit of life and all the organisms are made up of one or more cells. In multicellular organism, such as tree, the cells together make up a structure, which perform a particular function and it is called tissue. The group of different tissues together form an organ and the organ together form a organ system. The higher organism exhibit organ system level of organisation. The presence of different organ system allow them to divide the labour in the body, hence, allow to perform multiple processes in synchronisation, so that the organism can perform all the task essential for living.

the cell theory states that all living things including animals, as well as plants, are made of cells.