Question

What are vertebrates ? What are the five classes? what are their main features ?

Answer 1

Vertebrate Classification

Vertebrates can be subdivided into five major groups: fishes, amphibians, reptiles, birds, and mammals. Amphibians, reptiles, birds, and mammals are ranked as classes. The fishes includes five different classes: Myxini, Hyperoartia, Chondrichthyes, Actinopterygii, and Sarcopterygii. All of the existing classes of vertebrates are listed in Table below with their major features. In addition to the existing classes, there are a number of extinct classes of vertebrates that provide important information regarding vertebrate evolution, which we will examine in the next section.

Major Distinguishing Features of Each Class Within the Vertebrate Subphylum

Class Major Features Example

Myxini (hagfish)

True backbone absent but cranium present

Jawless

Cartilaginous endoskeleton

Hagfish

[Figure 2]

Hyperoartia (lampreys)

Some backbone features on notochord, also has cranium

Jawless

Cartilaginous endoskeleton

Lamprey

[Figure 3]

Chondrichthyes (sharks, rays)

True backbone

Jaws

Cartilaginous endoskeleton

Shark

[Figure 4]

Actinopterygii

Bony endoskeleton

Ray-finned

Perch

[Figure 5]

Sarcopterygii

Bony endoskeleton

Lobe-finned

Coelacanth

[Figure 6]

Amphibians (frogs, salamanders)

Lungs as adults

Tetrapods – 4 limbs for terrestrial movement

Ectothermy

Frog

[Figure 7]

Sauropsida (reptiles)

Lungs throughout life

Amniotic egg

Ectothermy

Alligator

[Figure 8]

Aves (birds)

Endothermy

Feathers

Forelimbs are wings

Bird

[Figure 9]

Mammals

Most do not lay eggs – internal development

Hairy bodies

Neocortex

Mammary glands produce milk to nourish young

Bear

[Figure 10]

Classification of vertebrates is not static, and there are currently different schools of thought regarding how they should be subdivided and ranked. For example, there are some groups that do not consider Hyperoartia to be a class, but rather consider to to be a currently unranked group. There is also controversy regarding the hagfish of the class Myxini. In the last chapter you learned that hagfish do not contain a true vertebral column, yet they do have a cranium surrounding their brains and are therefore often considered as a separate group from the three main chordate subphyla (tunicates, cephalochordates, and vertebrates). For the purposes of this chapter, we will consider both Hyperoartia and Myxini to be classes within the subphylum Vertebrata.

Answer 2

Answer :

Definition

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Vertebrates :- They are the animals included in the phylum chordata in which the spinal chord is made small vertebrate.

                                                                                                                                             

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The five classes are :-

• Pisces
• Amphibians
• Reptiles
• Aves
• Mammalia

                                                                                                                                                                           

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Features :-

• They possess a solid notochord.
• The body has bilateral symmetry.
• They have a true vertebral column.
• They have a dorsal hollow nerve cord.
• They are triploblastic.
• They are coelomate.

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Hope it helps you

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