what is the difference between agnatha and gnathostomata?

Differences between Agnatha and Gnathostomata

Agnatha

Gnathostomata

1. Mouth is circular and without jaws.

2. Paired appendages are not present.

3. Notochord is present throughout life.

4. There are 8 or 10 pairs of cranial nerves.

5. Only a single median nostril is present.

6. There are no organized pancreas and spleen.

7. They are cold blooded.

1. Mouth has jaws

2. Paired appendages (fins and limbs) may be present.

3. Notochord is present in the embryonic stage and in adult it is replaced by a vertebral column.

4. There are 10 or 12 pairs of cranial nerves.

5. Paired nostrils are present.

6. Pancreas and spleen are present as distinct organs.

7. They may be cold-blooded or warm blooded animals.

Differences between Pisces and Tetrapoda

Pisces

Tetrapoda

1. Fishes have paired appendages in the form of pectoral and pelvic fins.

2. They may possess an exoskeleton of dermal scales.

3. Fishes respire by means of gills.

4. Except lung fishes they do not have internal nares.

5. Heart is 2 chambered except lung fishes where heart is 3 chambered.

6. Fishes have internal ears.

7. All fishes are aquatic.

1. Tetrapods have paired appendages in the form of five digited (pentadactyl) limbs.

2. They may possess an exoskeleton of epidermal scales, feathers or hair.

3. Tetrapods respire by lungs. Some amphibians also respire by buccopharyngeal cavity, skin and gills.

4. They have internal nares.

5. Heart is three or four chambered.

6. Tetrapods may have internal and middle ears or internal, middle and external ears. Snakes lack ears.

7. Both aquatic and terrestrial forms are present.