Living things need certain substances to move, grow and keep themselves alive. Animals eat plants or other animals as their main source of nutrition.
This food is chemically complicated and must be reduced to simpler materials by a process called “digestion”. Chemicals in the body break down the nutrients in food, which the body then uses for growth and energy. Waste materials are then excreted by the body.
Photosynthesis
Plants and animals depend on each other for feeding and breathing. Plants take carbon dioxide from that air and absorb water and minerals from the soil. They use the Sun’s energy to convert these simple substances into sugars and starches and produce oxygen. This is called “photosynthesis”.
Animals, like gorillas, use plants as a source of food. They also breathe in the oxygen that plants release. Animals produce carbon dioxide which they breathe out and they excrete waste water and chemicals from their bodies. Plants depend on all these substances.
Plants need oxygen in order to carry out certain life processes. Plants use photosynthesis to produce oxygen but they also absorb oxygen from the soil (through their roots) and from the air (through small holes in their leaves).
At night, plants take oxygen from the air because there is not enough sunlight for photosynthesis to take place. During the day plants produce their own oxygen – much more than they need. This excess oxygen is released into the air.
Plants provide oxygen for humans and animals to breathe.
Squirrels need to eat about a pound of food a week to maintain an active life.