With such a long list of believable theories to chose from, including spontaneous generation, biogenesis and chemical evolution, it is hard to decide which is the most likely to have been the reason why the earth is currently bustling with life forms. However, I feel that the chemical evolution theory is most believable, due to the evidence provided by Stanley Miller and Harold Urey that chemicals in the early atmosphere can produce amino acids, which are the building blocks of life. So now that I may have an idea of how life got started, it still leaves you wondering what exactly is meant by being alive. Life is characterized by such elements as having cells, reproduction, using energy, metabolism, etc. However, there is much more to life than being composed of cells and respiration, although there would not be life without these fundamental elements.
Life is a partnership between every living organism.
We re all dependent on each other to perform the basic tasks needed to keep us alive, such as breathing. Animals are dependent on plants for oxygen, while plants are dependent on animals for Carbon Dioxide. Without each other both plants and animals would not be able to perform the basic function of respiration, and there could be no life.