Brent Cornell

    
Chordates are animals that possess certain key features in an embryonic state that may persist into adulthood 

• These features include a notochord, hollow dorsal neural tube, pharyngeal slits and a post-anal tail

In some chordates, the neural tube will develop into a spine and the notochord will form a protective backbone

• These chordates are grouped into a sub-phylum (vertebrata) and include birds, mammals, amphibians, reptiles and fish

Fish

• Covered in scales made out of bony plates in the skin
• Reproduce via external fertilisation (egg and sperm released into the environment)
• Breathe through gills that are covered with an operculum
• Does not maintain a constant internal body temperature (ectothermic)

Amphibian

• Moist skin, permeable to gases and water
• Reproduce via external fertilisation (usually spend larval state in water, adult state on land)
• Can breathe through skin but also possess simple lungs
• Do not maintain a constant internal body temperature (ectothermic)

Reptiles

• Covered in scales made out of keratin
• Reproduce via internal fertilisation and females lay eggs with soft shells
• Breathe through lungs that have extensive folding (increases SA:Vol ratio)
• Do not maintain a constant internal body temperature (ectothermic)

Birds

• Covered in feathers (made out of keratin)
• Reproduce via internal fertilisation and females lay eggs with hard shells
• Breathe through lungs with parabronchial tubes
• Maintain a constant internal body temperature (endothermic)

Mammals

• Skin has follicles which produce hair made out of keratin
• Reproduce via internal fertilisation and females feed young with milk from mammary glands
• Breathe through lungs with alveoli
• Maintain a constant internal body temperature (endothermic)

Vertebrate Classes Recognition Features:

Overview of Vertebrate Classes