I learned that predators (such a humans, lions, wolves etc) have eyes that face the front to hunt down prey, whereas prey animals have eyes on either side to give them a wide field of view to spot predators.
How come sharks (apex predators) still have eyes on either side and not front facing?
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There’s a tradeoff between having eyes facing front close together and eyes widely spaced facing more or less off to the side. Front facing eyes enable better distance determinations due to stereoscopic imaging, but they yield a smaller field of vision. Widely spaced eyes have a larger field of vision, making it easier to see more of the area around an animal, but they are not nearly as good at determining distance “at a glance.” Lots of land based animals have evolved front facing eyes because it’s easy to see greater distances in air versus water, so being able to determine distance with greater precision is critical (for both predator and prey). This has limited many land based animals’ field of vision, which they’ve dealt with by having generally more mobile necks (think of an owl v. a fish). Most of the ocean is fairly opaque and dark, so it’s hard to see large distances even if you had forward facing eyes. In other words, forward facing eyes in the ocean confer far less advantage than they do on land. However, being able to see what’s coming up behind you is really important in the ocean where things can appear out of the murkiness and be close by – you really can’t see them coming from a mile away. Evolutionarily speaking, sharks have more to gain by having larger fields of vision even if it limits their ability determine distance visually (something they more than make up for with their heightened sense of smell and their unique sensory system that detects miniscule changes to electric fields in water, which are often caused by the presence of other living things swimming close by).
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