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The movement of a substance from an area of high concentration to an area of lower concentration. One of the ways a substance can move in and out of a cell across the cell membrane. 

Mitosis: One division occurs, two identical cells are formed, occurs in body cells involved in growth and repair. 

Meiosis: Two divisions occur, four cells with genetic variation are form...

Breathing begins with inhalation. This starts with the contraction of the diaphragm, which flattens on contraction pulling the lungs down. The intercostal muscles contract to move the lungs up and out....

Blood is made of many components, one of them being red blood cells. These are responsible for carrying oxygen around the body. Haemoglobin is the protein molecule within red blood cells that binds to ...

Scientists have come up with many different definitions of a species over the years; reproductive isolation being key to all concepts. However the most widely accepted is the biological species concept: '...