Your question is actually one on which the whole of life on earth depends. One of the BIG questions in life! Plants have several magic tricks which they can do that no other organisms on earth can do. 1) Plants can change the energy in sunshine into energy in chemicals. When we eat plants, it is that energy which we tap into and use for our own needs – running, thinking, breathing etc etc. 2) Plants can make sugar from Carbon dioxide and Water (with the help of the energy from the sun). So, the sugar which we put in our tea and the sugars which are found in fruits and other sweet foods all come from air and water! Plants store spare sugar as starch and that is one of the main chemicals which we eat for energy in bread, potatoes, cereals, rice etc. 3) Plants can make those simple sugars into complicated chemicals.
We rely on plants to make proteins for us and we need proteins for our growth. We cannot make our own proteins – we need plants to do that for us. The same is true of vitamins and partly so for fats and oils. 4) Plants turn Carbon dioxide in the air into Oxygen. Oxygen is the waste product of photosynthesis (the name for the chemical which plants use to do all this) and this is just what we need to breathe in to enable us to release the energy from sugars. Our waste product of this process is Carbon dioxide which we breathe out and plants need for photosynthesis. (A sort of mutual sharing – plants need animals nearly as much as animals need plants). For plants to do all this, they need chlorophyll which does the magic of capturing sunlight and making the energy available for powering the reactions of photosynthesis.
John Hewitson David R. Hershey expanded their list:
lants help the environment (and us! ) in many different ways: lants are the only organisms that can convert light energy from the sun into food. And plants produce ALL of the food that animals, including people, eat. Even meat. The animals that give us meat, such as chickens and cows, eat grass, oats, corn, or some other plants. ne of the materials that plants produce as they make food is oxygen gas. This oxygen gas, which is an important part of the air, is the gas that plants and animals must have in order to stay alive. When people breathe, it is the oxygen that we take out of the air to keep our cells and bodies alive. All of the oxygen available for living organisms comes from plants.
Plants are the primary habitat for thousands of other organisms. Animals live in, on, or under plants. Plants provide shelter and safety for animals. Plants also provide a place for animals to find other food. As a habitat, plants alter the climate. On a small scale, plants provide shade, help moderate the temperature, and protect animals from the wind. On a larger scale, such as in tropical rainforests, plants actually change the rainfall patterns over large areas of the earth\’s surface. n the forest and the prairie, the roots of plants help hold the soil together. This reduces erosion and helps conserve the soil. Plants also help make soil. Soil is made up of lots of particles of rocks which are broken down into very small pieces.
When plants die, their decomposed remains are added to the soil. This helps to make the soil rich with nutrients. any plants are important sources of products that people use, including food, fibers (for cloth), and medicines. Plants also help provide some of our energy needs. In some parts of the world, wood is the primary fuel used by people to cook their meals and heat their homes. Many of the other types of fuel we use today, such as coal, natural gas, and gasoline, were made from plants that lived millions of years ago. lants, because of their beauty, are important elements of out human world. When we build houses and other buildings, we never think the job is done until we have planted trees, shrubs, and flowers to make what we have built much nicer.