Cellular Respiration and Photosynthesis<span> are </span>almost opposite processes<span> because </span>photosynthesis<span> removes carbon dioxide from the atmosphere while </span>cellular respiration<span> puts back carbon dioxide. </span>Cellular respiration<span> uses oxygen and has its waste product of carbon dioxide (CO2).</span>
<span>Stomach. Stomach which connects oesophagus to small intestine is the main part of digestive system where digestion occurs. Protein is a necessary food content for the healthy being of body. From the food proteins are liberated and its chemical digestion starts in the stomach.</span>
Unicellular organisms excrete waste by a contractile vacuole. A vacuole is membrane-enveloped organelle in a cell that is found in lots of microorganism. It expands, filling with water then contracts, removing all of its contents to the exterior of the cell.