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.
Chloroplasts use this energy to create sugar molecules that help the plants grow and reproduce. Then, animals come along and eat the plants and absorb their energy. They use the energy obtained from the plants to produce their own energy and convert it into water and carbon dioxide. Plants use the carbon dioxide and water, and the cycle begins again. In order to obtain energy, animals do not always have to eat plants. They can also get energy from eating other animals that eat plants. There are many different processes that go on in plants and animals that require energy. Synthetic work involves things like the production of DNA, and it requires energy to occur.