Lesson56 Balance of Nature

All the different plants and animals in a natural world are in a state of balance. This balance is achieved by the plants and animals interacting with each other and with their non-living surroundings. An example of a natural community is woodland, which is usually dominated by a particular species of plant, such as the oak tree in an oak wood. The oak tree in this example is therefore called the 1 but there are also many other types of plants, such as bushes, 2 , mosses, lichens and algae.

　　The plants of a community use carbon dioxide, oxygen, water and nitrogen to build up their tissues using energy in the form of 3 . The plant tissues form food for the plant-eating animals which are in turn eaten by the 4 animals. Thus plants produce the basic food supply for all the animals of a community. The animals themselves are the consumers, and are either herbivores or carnivores.

　　Examples of herbivores in a woodland community are rabbits, deer, mice, snails, and insects. The herbivores are sometimes eaten by the carnivores. Woodland carnivores are of all sizes, from insects to animals like owls, and foxes. Some carnivores feed on herbivores, some feed on the smaller carnivores, while some feed on both. These food relationships between the different members of the community are known as food chains or 5 . All food chains start with plants. The links of the chain are formed by the herbivores that eat the plants and the carnivores that feed on the herbivores.