How does the organ level of organization differ in plants & animals?

The organ level of organization is much less definite in plants than it is in animals. At most, we might distinguish roots, stems, leaves, and reproductive structures. Clear-cut functions, the distinguishing features of organs, can be assigned to each of these structures. Roots are involved in anchoring the plant and procuring water and minerals. The shoot or stem supports the entire plant, while the leaves are primarily organs for food procurement. Flowers or other reproductive structures are involved in producing progeny for the next generation.
In animals, organ development is far more complex and defined. Organs are parts of organ systems where total functions are carried out. Thus, excretion is handled by the kidneys, ureters, bladder, and urethra. The nervous system consists of the brain, spinal cord, and peripheral nerve network. Associated with the complexity and discreteness of the organ systems of animals is a far greater range of functions and activities than is found in plants.