Zoology - Wikipedia

Chondrichthyes (/kɒnˈdrɪkθᵻ.iːz/; from Greek χονδρ- chondr- 'cartilage', ἰχθύς ichthys 'fish') is a class that contains the cartilaginous fishes: they are jawed vertebrates with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone. The class is divided into two subclasses: Elasmobranchii and Holocephali. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.

  Agnatha: Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present and extinct species. The group excludes all vertebrates with jaws, known as gnathostomes. The agnathans as a whole are paraphyletic, because most extinct agnathans belong to the stem group of gnathostomes. Recent molecular data, both from rRNA and from mtDNA as well as embryological data strongly supports the hypothesis that living agnathans, the cyclostomes, are monophyletic. The oldest fossil agnathans appeared in the Cambrian, and two groups still survive today: the lampreys and the hagfish, comprising about 120 species in total. Hagfish are considered members of the subphylum Vertebrata, because they secondarily lost vertebrae; before this event was inferred from molecular and developmental data, the group Craniata was created by Linnaeus to reference hagfish plus vertebrates. In addition to the absence of jaws, modern agnathans are characterised by ab

Chordata :   There are many members of animal kingdom. They are different in class and genus. The animal kingdom are divided on 9 or 10 phylum. Chordata is one of them. Only chordates have bone in animal kingdom. Character of chordates.......  1. Chordates have spinal cord in their embroionic stage.  2. They have Pharynx cave.  3.  Chordates have ear . They are covered by hair. Some females of chordates feed breast to their child. Chordates are divided in to  3 sub- phylum. Like a) urochordata b) Chefalochordata and c) Vertebrata. Vertibbrates are huge in number all over the world. The sub - phylum vertebraes are divided into 8 classes olso depends on their physical structure.  Like as......... 1. Agnatha. 2. Chephalaspidomorphi . 3. Chondricthyes. 4.OOstiecthyes. 5. Amphibia. 6. Reptilia. 7. Aves. and 8. Mamalia. 1. Agnatha :  They have a straight body. They have sucker mouth. They lives in in under water mud. Like...     Mayxine glatinosa

Cell :         The cell is the functional and formation unit of animals. Every animals makes with only one to millions or trillions cell. All vital importance things are held in cell. Even a cell individualy can alive. That's why you can say to a cell is a animal. Some Bacterias and virus can alive individualy although they have only one cell. At first zoologist Robert hook discovered the cell. Animal cell made with plasma membrane, cytoplasm, nucleus, mitochondria, microbiuls, ribosom, lisosom, endoplasomic reticulam, Cell cavity etc.            The plasma membrane protect cell from osmotic pressure and save all cellular things. Cytoplasm is the liquid media of cell. All micro elements of cell are stay at here. Every cell have a neucleous. Neucleous contain genetic things. On the others hand cell contain may mitochondria and it's known as power house of cell. Cell can be two kinds depend on their structure. Like as.....           1. Eukaryotic cell