Good question! I bet you know that it is plants that can carry out photosynthesis, so we have to think about at least two things in order to answer your question. First, what is photosynthesis and what do plants use it for? And second, why then would animals need photosynthesis? Phrased another way, why do animals depend on photosynthetic plants?

Let's start with photosynthesis. I bet you can find a textbook definition of this process, but try putting it in your own words. Here is an example from a college level textbook:

"The process by which the energy in light is captured and used to synthesize carbohydrates."

So, in other words, plants can capture light from the sun and turn it into sugar, which is used for energy. And energy is what the plant needs to grow and reproduce. No photosynthesis, no plants. That takes care of part one.

Now move on to the question of why animals need plants. This has to do, of course, with foodwebs. Pick your favorite foodweb and note where the plants are located and how many animals they can affect.

No sun light, no photosynthesis. No photosynthesis, no plants. No plant, no food for lots of animals that eat plants (herbivores). No herbivorous animals, no food for animals that prey on the herbivores. So, basically no photosynthesis, no animals. And it's important to remember that humans are animals and that we are in the food web communities as well!

Photosynthesis is a process used by plants, some unicellular organisms, and microorganisms. These organisms are vital to life on earth as they provide oxygen as well as food. Photosynthetic organisms take light energy and use it to make their own "food". In this process they use carbon dioxide and light to make sugars and oxygen. This is great for other animals that utilize this oxygen and eat the plants for food.

Animals need to get their energy from other living things, but in order to do that said other living things need to have energy for the animals to get.Photosynthesis is the means by which plants and algae get their energy. Animals also need elemental oxygen,and photosynthesis produces this as a waste product as well.