SUB-PHYLUM: VERTEBRATA/CRANIATA
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These are the organisms in which norochord is replace by vertebral column.
Super Class: Pisces-Fish
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Habitat: These vertebrate animals are exclusively aquatic. They inhabit fresh, marine and brackish water.
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Body design: Their body is spindle shaped, stream lined with a muscular tail that helps them to swim. They have lateral line system that helps them to know the disturbances in the near by environment. The system is a unique sense organ.
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Limbs: They have paired appendages in the form of fins. Unpaired fins are also present. Fins help in balancing during swimming.
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Exoskeleton: Skin is glandular which is covered with dermal scales. These scales arise from the dermis layer hence are deep seated. The scales provide them protection.
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Endoskeleton: Internal skeleton is either cartilaginous or bony.
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Body temperature: organisms of this group are cold blooded, i.e. their body temperature varies with the change in surrounding/ environmental temperature.
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Respiration: Respiration is typically by pharyngeal gills, varying from 5 to 7 on each side. Gills may be covered with a flap like membranous structure known as operculum. Exceptionally some respire through lungs.
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Circulatory system: Closed circulatory system present with two chambered heart and blood vessels. Heart is comprised of one ventricle and one auricle.
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Reproduction: they are unisexual organisms that reproduce by sexual mode. Fertilization is external, exceptions are there. Female lays unfertilized eggs [Oviparous] in water which is fertilized by sperms released by males.
Examples:
Chondrichtyes
Osteoichtyes