It is found that the Sun is the major source of energy on our planet and “sunlight is pure energy”ť (Silverstein et al. 4). Â All living things need the energy that should be used in different life processes: for movement, growth or reproduction function. Â According to the cell theory, all living beings on our planet are composed of the cells. Cells need the energy. Practically all living things get the energy they need from the light of the sun, directly or indirectly.
For example, green plants get the energy they need from the process of photosynthesis in which the energy of light is converted into chemical energy (Silverstein et al. 4). The cells of the plants’ leaves contain chloroplasts which can absorb light from the Sun. The green pigment chlorophyll in the chloroplasts can interact with the light of the Sun. In this case, the plants use the energy of the Sun to convert water taken from the soil and carbon dioxide taken from the air to make sugar (Silverstein et al. 5). It means that the energy comes directly from the Sun. In addition, during the process of photosynthesis, oxygen is given off in the form of a by-product and it is used by all living beings to get energy they need out of food. In other words, in the bodies of all living things on Earth, oxygen is used to burn food for energy.
However, animals get the energy by eating plants or other animals. The food they eat contains energy. It means that in this case, the energy in the food comes indirectly from the Sun. When human beings eat plants, these plants are converted back to the energy which helps to power human bodies and provides the appropriate nutrients, vitamins, minerals, etc. contained in the plants. It means that for human beings, food is the major source of energy.