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.
Both plants and animals carry out metabolism, but they acquire the energy for this process by different means, i.e. plants employ photosynthesis and animal eat. Plant require very little energy compared to animals. Plant metabolic activities provide energy for transpiration, growth, etc.