<P> Magnetoreception (also magnetoception) is a sense which allows an organism to detect a magnetic field to perceive direction, altitude or location . This sensory modality is used by a range of animals for orientation and navigation, and as a method for animals to develop regional maps . For the purpose of navigation, magnetoreception deals with the detection of the Earth's magnetic field . </P> <P> Magnetoreception is present in bacteria, arthropods, molluscs and members of all major taxonomic groups of vertebrates . Humans are not thought to have a magnetic sense, but there is a protein (a cryptochrome) in the eye which could serve this function . </P> <P> An unequivocal demonstration of the use of magnetic fields for orientation within an organism has been in a class of bacteria known as magnetotactic bacteria . These bacteria demonstrate a behavioural phenomenon known as magnetotaxis, in which the bacterium orients itself and migrates in the direction along the Earth's magnetic field lines . The bacteria contain magnetosomes, which are nanometer - sized particles of magnetite or iron sulfide enclosed within the bacterial cells . The magnetosomes are surrounded by a membrane composed of phospholipids and fatty acids and contain at least 20 different proteins They form in chains where the magnetic moments of each magnetosome align in parallel, causing each bacterium cell to essentially act as a magnetic dipole, giving the bacteria their permanent - magnet characteristics . </P>

What organisms are able to sense earth's magnetic field and why