Why are sharks attracted to blood?
There are two types of answers to biological questions like this, a mechanistic or physiological answer, and an evolutionary one. The physiological answer is that they have specialized cells that can detect blood. I actually do not know the details of this mechanism, but the same basic principles many (if not all) sensory processes. A protein called a receptor sits in the cell membrane, and sticks out so that it is exposed to the environment outside the cell. It binds to specific chemical signals, and when it does so it passes this signal along to the inside of the cell. The signal is ultimately sent to the brain, where it initiates a behavioral change in the animal, in this case directing it toward the source of the blood. My guess is that sharks sense a protein like hemoglobin that is common in blood. Where there’s hemoglobin, there’s likely to be an injured animal. The signal molecule may be some other substance that is found in blood, and it could very well be that sharks respond t
