ZOOLOGY OF CHORDATES STUDY GUIDE - Zakharenko M.O. - 2015

SECTION 2. SUBPHYLUM VERTEBRATES, OR CRANIATES - VERTEBRATA, SEU CRANIATA

This subphylum comprises highly organized Chordates. They are characterized by active feeding, accompanied by increased mobility and a complete reorganization of the Locomotor System. The notochord is gradually replaced by the spine, and a Skull develops, subsequently giving rise to jaws. Paired limbs appear in certain superclasses. The metabolic rate is significantly elevated due to the intensification of feeding, Digestion, Respiration, Circulation, and excretion. The Structure and function of the Central Nervous System, Sensory Organs, and hormonal regulation become substantially more complex. Consequently, animal behavior and population structure are enhanced. The overall level of vital activity rises, the reproductive apparatus becomes more complex, and parental care is strengthened. All these adaptations have driven the global distribution of vertebrates across all ecosystems. Vertebrates comprise approximately 42,000 species.

The General characteristics of vertebrates are:

- the central nervous system extends significantly forward relative to the notochord;

- a cartilaginous or bony Skeleton surrounds the notochord;

- the skeleton is represented by THE Vertebral Column;

- the vertebral column is of mesodermal origin;

- the central nervous system is represented by the Brain AND SPINAL cord;

- the brain is enclosed in a protective case, the skull;

- a closed Circulatory system, always with a Heart;

- respiratory organs: gills in aquatic forms, Lungs in terrestrial ones;

- excretory organs are Kidneys;

- independent, differentiated sensory organs.

Vertebrates are the most diverse group of higher animals with varying Levels of Organization. The subphylum includes 2 divisions, 4 superclasses, and 11 classes.

Subphylum VERTEBRATES - VERTEBRATA, or CRANIATES - CRANIATA

1. Division JAWLESS - Agnatha, or ENTOBRANCHIATES - ENTOBRANCHIATA

Superclass CYCLOSTOMES Class CYCLOSTOMES - CYCLOSTOMATA

2. Division JAWED VERTEBRATES (GNATHOSTOMATA), or ECTOBRANCHIATES (ECTOBRANCHIATA)

Superclass Fishes - PISCES

Class Cartilaginous Fishes - CHONDRICHTHYES

Class Bony Fishes - OSTEICHTHYES

Superclass TETRAPODS - TETRAPODA, QUADRUPEDA

Class AMPHIBIANS - AMPHIBIA

Class Reptiles - REPTILIA

Class Birds - AVES

Class Mammals — MAMMALIA



Last update: 19/08/2026

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