No living creature can exist in complete isolation. An animal is bound to depend on other living creatures, ultimately plants, for its food supply. It must also depend upon the activities of plants for a continued oxygen supply for its aspiration . Apart from these two basic relationships, it may be affected directly or indirectly in countless different ways by other plants and animals around it. Other animals prey on [it] or compete with [it] for the same food. Plants may provide shelter, concealment or nesting material, and so on. Similarly, the animal will produce its own effects on the surrounding plants and animals: some it may eat or destroy and for others it will provide food. Also, through its contribution of manure, it may influence the texture and fertility of the soil.

여기서 it이 지칭하는 것이 먼가요?
또 some it may eat or destroy and for others it will provide food 여기서 some의 문장성분은 먼가요? some앞에 for가 있어야 될 것 같기도 하고... 음..