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.
Animals depend on plants for food as plants produce food and energy which animals can't, so, herbivores eat plants to get energy, carnivores eat herbivores and other carnivores for energy and omnivores eat all four, plants, herbivores, carnivores and also other omnivores for energy.
#2. phyzguy Science Advisor. The nutrients that plants get from the soil don't generally include living organisms. For the most part, plants don't require eating other organisms as a source of energy, and animals do. Most plants get their energy from the sun instead of eating other organisms. There are some exceptions, like Venus fly-traps, which are plants that eat insects for nutrients (not for energy), and animals like worms that eat primarily dead organic matter.