Skeletal System:
* Sharks: Have a cartilaginous skeleton, which is lighter and more flexible than the bony skeletons of most fish.
* Other fish: Have a bony skeleton.
Skin:
* Sharks: Have rough, sandpapery skin covered in tiny, tooth-like scales called dermal denticles. These scales are tough and reduce drag in water.
* Other fish: Have smooth, slimy skin covered in scales that vary in type and size depending on the fish species.
Gills:
* Sharks: Have 5-7 gill slits on each side of their head that are separate openings.
* Other fish: Usually have one gill cover (operculum) that covers all their gill slits.
Mouth:
* Sharks: Have a mouth located on the underside of their head. They have multiple rows of teeth that constantly grow and replace old ones.
* Other fish: Have mouths located on their upper snout and typically have one set of teeth.
Buoyancy:
* Sharks: Lack a swim bladder for buoyancy and instead use their large, oily livers to help them stay afloat. This also allows them to be more agile.
* Other fish: Have a swim bladder, an internal gas-filled sac that helps them maintain buoyancy.
Reproductive System:
* Sharks: Most species are viviparous, meaning they give birth to live young. Some are ovoviviparous, meaning they give birth to live young that developed from eggs.
* Other fish: Most species are oviparous, meaning they lay eggs.
Other Notable Differences:
* Sharks: Have excellent sense of smell and electroreception (ability to detect electric fields), which helps them locate prey. They also have a large, powerful tail that provides propulsion.
* Other fish: Some species possess specializations like sharp spines, venom glands, or bioluminescence, depending on their environment and lifestyle.
In essence, sharks are highly adapted predators with a unique anatomy that allows them to be successful in their marine environment. They are distinct from other fish in several key areas, even though they share common ancestry.