Vertebrates Characteristics: Learn Features and Quiz

Study Notes

Vertebrates have a well-developed head due to cephalization
They have a metameric body organization
They have an endoskeleton
They have a vertebral column (vertebrae) which supports the trunk
The vertebral column is a series of metamerically arranged internal pieces of cartilaginous or bony skeleton
The anterior part of the nerve cord is enlarged to form a brain
The brain is protected by a brain case called cranium or skull
The cranium has functions such as protection of the brain and orbits of the eyes, muscle attachment, and connecting the brain and other head organs to the rest of the body

Special sense organs called receptors are associated with the brain (e.g. eyes, ears, nose, tongue)
The pharynx is small and the gill slits are few in number and often absent in adults
Vertebrates have a chambered heart for rapid blood circulation
They have a closed circulatory system with distinct blood vessels
Red blood corpuscles contain haemoglobin to carry large amounts of oxygen
Excretory organs are kidneys, which remove wastes and regulate the internal environment
Endostyle is present in ammocoete larva of lampreys and is transformed into thyroid gland in other vertebrates
Sexes are mostly separate, fertilization may be external or internal, and development may be direct or indirect through a larval stage

There are two superclasses of vertebrates: Agnatha (jawless fishes) and Gnathostomata (jawed vertebrates)
There are six classes of jawed vertebrates: Chondrichthyes (cartilaginous fishes), Osteichthyes (bony fishes), Amphibia (amphibians), Reptilia (reptiles), Aves (birds), and Mammalia (mammals)

Common name: Jawless fishes or jawless vertebrates
Examples: Lamprey and Hagfish
Features: most primitive vertebrates, many agnathans are extinct, no jaws, true teeth are absent
Body is elongated and eel-like in shape
Living agnathans do not have scales; skin is slimy
Adults are parasitic and marine, while larvae are free-living filter feeders on plankton, algae, and detritus in freshwater
Hagfishes are exclusively marine

Mouth of adult lamprey is circular and modified into a sucker with horny teeth and hooks
Hagfish has tentacles round the mouth to detect food and a tongue-like structure with hooks to capture prey
No paired appendages, but have fins which are not in pairs
Single median nostril leads to a single median olfactory organ
Skeleton is cartilaginous
Embryonic notochord persists in the adult
Gills are not protected or supported by gill arch
Seven or more paired gill pouches are present
Heart has two chambers
Kidneys are adapted for excretion and regulating salt balance in both fresh and marine waters
Most agnathans are hermaphrodites, fertilization is external