Passage 1: Two or more individuals trying to use the same resource, such as food, water, shelter, space, or sunlight, is called competition. Because resources are in limited supply in the environment, the use of them by one individual or population decreases the amount available to other organisms. Competition also occurs between individuals within a population. The elk in Yellowstone National Park are herbivores that compete with each other for the same food plants in the park. According to passage 1, competition occurs between which of the following?