MODULE 4: SUBPHYLUM VERTEBRATA

4.1. Module Objectives.

At the end of the lesson the learner will be able to:

1. Define the Subphylum Vertebrata.
2. Describe the characteristics of the Subphylum vertebrata.
3. List the super classes of the Subphylum vertebrata.

4.2. Introduction

The subphylum Vertebrata comprises of the most successful animals on earth. They colonize all ecosystems, terrestrial, aquatic and arboreal. This success could be attributed to a host of factors ranging from the efficient control and coordinating system, efficient blood circulatory system, strong skeletal system and the ability to regulate internal body temperature.

Common vertebrates are fishes, frogs, lizards, birds and man

4.3. Basic characteristics of Vertebrates.

Some of the basic characteristics of Vertebrates are:

The first three groups are commonly called fishes, while the remaining four groups are called tetrapods (they posses four limbs, called tetraapod limbs).

4.3.1 Skeletal system.

Vertebrates possess  a vertebral column. The vertebral column helps in the support of the vertebrtae, given shape, sites for attachment of muscles aswell housing the spinal cord.

4.3.2. Cephalization.

Vertebrates are cephalized. They have well demarcated head(a distinct head, with skull enclosing a brain) and body regions.

Figure 1 Vertebral column

4.3.3. Respiratory system.

Vertebrates have efficient respiratory system, which ensures efficient metabolic rate.The respiratory system range from bucoo-pharyngeal, cutaneous in amphibians to the pulmonary system in man.

Figure 2 Respiratory system of vertebrates

4.3.4.Control and coordination system

Vertebrates have well developed, complex control and coordinating system- The nervous system( complex brain and spinal cord), Sensory system, endocrine system and muscular system.

Figure 3 Nervous system of Vertebrates

4.3.5.Circulatory system

Vertebrates have efficient closed, double blood circulatory system, and the lymphatic system. The blood circulatory system comprised of the four chambered heart, blood, and blood vessels. Its main functions is the transportation of blood, food, nutrients and defense. While the lymphatic system, comprised of the lymphatic vessels , the lymph and the lymph nodes. The main functions of the lymphatic system is the transportation of lymph and defense of the body.

Figure 4 Vertebrate blood circulatory system

4.3.6. Support and movement

The locomotary organs of vertebrates range from fins, wings to limbs in man. Vertebrates have strong endoskeleton, comprising of strong pectoral and pelvic girdles. The pectoral and pelvic girdles lifts the body, provide support and aids in movement. Vertebrates possess tetrapod( four) limbs that aids in efficient support, movement on land or flight.

Figure 5 Evoloution of vertebrate locomotory organs

4.3.7. Homeostatsis

Vertebrates can be able to regulate their internal body environment within specific limits. A process known as Homeostasis. For examples vertebrates can be able to regulate their body temperature, salt concentration, water concentration etc within their bodies

4.4. Brief overview of vertebrate evolution .

First vertebrates were marine, lacking jaws or paired fins. Later on the jawless fishes were replaced by jawed creatures. Amphibian ancestors were the first to invade the land.  The Amphibians were later on replaced by the first group of reptiles called Dinosaurs. Dinosaurs and other reptiles ruled the earth for 150 million years. The Dinosaurs become extinct some million years ago and were replaced by the Aves and the mammals.

4.5. Classification of vertebrates

The vertebrates are composed of eight classes. Four classes are aquatic fishes. These are: