In the latter case the resistance is caused by dissipation of mechanical energy when the configuration or the direction of flow is sharply changed, by the formation of vortices and secondary flows as a result of the flow breaking away, by the centrifugal forces, etc.
Why do animals depend on plants. Plants give animals the food and shelter they need. Herbivores, which are plant eating animals, rely on plants to provide them with a regular source of food. They also provide shelter to may animals, both large and small.
Plants, on the other hand, depend on their cells to be extremely specialized to perform their life functions. For example, since plants do not have bones for structure and support they must have cell walls around all of their cells. This leads to the need for very unique cells in plants.