Photosynthesis is incredibly important in numerous ways. Everything in an ecosystem is a part of a food web. Trees, plants, flowers, shrubs, algae, etc. all need the sun in order to convert the suns light into energy. Here is an example that will make it easy to understand. All of the things I listed above cannot survive without using photosynthesis. So for example, there would be no trees. Without trees there would not be hiding places for a number of different animals. Since these animals did not have adequate hiding areas, they would be eaten very easily by predators. Since the predators are eating all of these animals, there would be a shortage of food for them and they may not survive. Every living thing is dependent upon another for survival in some way.
In addition, without the sun providing energy for all the "green" things on this planet, we would not have the oxygen that we need to survive. Without the sun, there would not be any ecosystems.
Photosynthesis is very important to humans and almost every single type of organism on earth. First of all if you think about it, a lot of animals that we eat, eats grass, and other plants. Without plants there wouldn't be enough animals for us to eat. Cows would be gone meaning most of the animals on earth will starve too. Before I get into a lot of details about how important photosynthesis is let me explain what photosynthesis is. I've bet you learned it almost hundreds of time so I'll shorten this explanation. Plants need a source of energy like we humans need food for energy they need the sun. They use the sun, carbon dioxide, and water for energy. They absorb the sun to form hydrogen and oxygen, and as humans breathe in oxygen we pass on carbon dioxide. It's like trading our air for their air. They suck in the carbon dioxide and you guessed it. They breath out oxygen, making it possible for us to breath again.
Now back to the explanation why photosynthesis is a huge part of our lives. Since without photosynthesis we wouldn't even be here on earth, meaning no oxygen. Without oxygen no other animals would live since there would be no plants. Most of them would suffocate in few seconds. I've read somewhere before in the past that if all of the sudden there was no oxygen the whole world would probably suffocate in 3 minutes. Most of the people would not be ready for it, as some coincidentally sucked in air the last second giving them a little more time.
There isn't much to go into detail with since it's really easy to understand once you read it.
Photosynthesis is important since without it most animals would die in seconds from suffocation without oxygen. Without oxygen means no food too, meaning no animals could eat grass/plants making all of the other organism on the food chain collapsing down into nothing. The whole world's organism would come to an end. Basically meaning everything wouldn't exist if it wasn't for Photosynthesis. Even us.
Hope this answers your question!
Photosynthesis is the building up of food components from water absorbed from the soil through the roots and carbon dioxide, absorbed through the stomata from the air along with the use of sunlight to split up water molecules to form hydrogen and oxygen.
Thus, oxygen is released and carbon dioxide is absorbed. This is a vital process. And the plants are called the producers because they are the only major living things that make their own food and as we can't photosynthesize (make our own food like the plants) so we will have to depend upon them and so is the other animals!!!
Photosynthesis is the process by which plants make their food using sunlight and the carbon-dioxide in the atmosphere. Without photosynthesis, there will be no plants in the ecosystem. Also there will be no way to convert the carbon-dioxide generated by animals to be converted back in oxygen and carbon.
The absence of plants, resulting from non-existence of the process of photosynthesis, will stat a chain of reactions that will end all animal life in the ecosystem. Animals are not able to produce the food they need for sustaining life. Animals cannot produce from simple chemicals, complex compounds required by them to create and sustain their life. They can only produce complex compounds required by them from other complex compounds produced by plants. In this way, animals get their food either from plants, or from the animals who live off plants. Thus without plants there will be no animals subsisting directly on food from plants. And in absence of such animals there will be no animals subsisting on food obtained from other animals. Thus without photosynthesis there will be no plant or animal life on earth.