Human beings are complex and special organisms as there is a complex organisation of cells in the human body. The organisation in the human body is summarised as follows: Cells—> Tissues—> Organs—> Systems—> Organism. The same type of cells which carry out a specific function are organised into a tissue. For example, a group of nerve cells form a nerve tissue. They are organised to work together to perform specific functions as the result of cells in the human body do not work individually. An organ is a group of tissue that cooperates to carry out a specific life process. For examples, epithelial tissues form blood vessels. Several organs are organised into a system.
Each system consist of several organs which are organised to carry out life processes such as respiration, reproduction and digestion. Various systems in the human body are well organised to carry out all the life processes efficiently. They are able to function because the cellular components work together to ensure the survival of human beings. The human brain is well developed to integrate information’s and store them as memory. This allows human beings to have the ability to talk, think rationally, create new things, learn from experience and use languages. The ability to do all these makes us really special compared to other organism.
Water is driven into the tanks to raise density and allow the submarine to sink and it also pumped out to reduce density and hence allow the submarine to float. The tanks can be filled with water and air, which allows the submarine to sink or rise in the water. When a submarine is floating, its ballast tanks are filled with air, which makes it less dense than the sea water it displaces hence allowing it to float. Submarines sink when water is let into the ballast tank. This is because the submarine’s density becomes greater than that of the surrounding water, resulting in negative buoyancy and causing it to sink.