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.
Why do living things, including plants and animals depend on each other in the environment to survive? Why Some animals actually do depend on others because of the food, but also through symbiotic relationships. Symbiotic relationships are when two creatures benefit by helping each other.