Plant, Human Being, Symbiosis

The first question is: What do we mean by the term “Plant world” (the Earth’s flora)? Most definitions include the trees, bushes, grasses, lianas, ferns and mosses-approximately 300,000 to 315,000 species. Some scientists also classify the marine green algae as a plant. Plants are characterized by their cellulose cell walls and their ability to extract from the sunlight the energy, necessary for their vital processes, through the process of photosynthesis. Plants are a crucial part of life on Earth. They are the major source of oxygen and are an essential element of most ecosystems, especially on land [2].