Diversity in Living Organisms

The sea lamprey (Petromyzon marinus) is a parasitic lamprey found in the northern Atlantic Ocean along shores of Europe and North America, in the western Mediterranean sea and in the shores of the Great Lakes. It belongs to superclass Agnatha (It is a superclass of jawless fishes). It is brown, gray, or black on its back and white or gray on the underside. The lamprey uses its suction cup-like mouth to attach itself to the skin of a fish and rasps away tissue with its sharp, probing tongue and keratinized teeth.

Adult lamprey may be characterised by toothed, funnel like sucking mouth. The common name 'lamprey' is probably derived from latin, 'lampetro' which may mean stone licker.

Petromyzon (lampreys) are all carnivorous and are true predators. The method of attack is very peculiar. It attack fishes, turtles etc and it attach themselves by suctorial mouth which is circular in shape. Mouth acts a sucker, it rasps the flesh of the prey with its tongue. Teeth which are situated around the mouth sink into the flesh of the prey and serve it to hold properly. 

Metazoa is the term given to the fully developed complex organism having tissue level organization. Kingdom Animalia is considered as metazoa. All the members of this kingdom are multicellular, eukaryotes. They are heterotrophs, they depend on other organisms directly or indirectly for food. Most of the organisms are motile which means they can move independently and spontaneously. 

Vertebrata is the most important part of chordate and is distinguished by a backbone (made either of bone or cartilage) having bones known as vertebrae and a skull enclosing a brain. The nervous system is entirely protected by these structures and also maintains the shape of the body.

Vertebrata is the most important part of chordate and is distinguished by a backbone (made either of bone or cartilage) having bones known as vertebrae and a skull enclosing a brain. The nervous system is entirely protected by these structures and also maintains the shape of the body.

Cyclostomes (like lampreys) are jawless vertebrates that are often ectoparasites on other fishes. Option C is wrong because Ciona is a Urochordate, not a Cephalochordate.

• They are jawless.
  
• They have a single median nostril.
• Their mouth is suctorial and circular.
• Body is elongated but no paired appendages or fins are present i.e. fins are unpaired.

Agnatha is the superclass of jawless vertebrates.

Petromyzon is an ectoparasite and belongs to the class Cyclostomata. Adamsia is Cnidaria, Ichthyophis is Amphibia, and Isimutus is not a standard biological name.

The class Cyclostomata is characterized by circular mouth without jaws. They have retractable horny teeth. Also, the scales and fins are absent in these members of the class. They are ectoparasites and don't have mucus glands on their skin.

Ostracoderms refers to the armored jawless fishes of the Paleozoic era. They lived in what is now North America, Europe, and Russia from the Middle Silurian to Upper Devonian. They were the first fish to use gills just for respiration. This is the first class of vertebrates. 

Agnatha which means 'no jaws' is a superclass of jawless fish in the phylum Chordata, consisting of both present (cyclostomes) and extinct species like ostracoderms. The body is covered in skin, with neither dermal or epidermal scales. Hagfish and Lampreys are a very common example.