Classes and General characteristics of Vertebrates

Class : Agnatha

Endoskeleton is cartilaginous , The body is thin , long and eel-like , with no paired fins , The mouth is circular , funnel-shaped contains a rough tongue that provided with many horny teeth and it is jawless , such as Lamprey .

Feeding : They are parasites , where they stick by their mouth into big fishes and attach themselves by the teeth , then they snap the flesh of these fishes by their rough tongue which is similar to the rasp .

Class : Chondrichthyes

Habitat : They live in salt water as seas , Endoskeleton is cartilaginous , The body is covered with scales similar to the teeth .

The mouth is ventral , It lies on the ventral surface of head and provided by two jaws carry several row of teeth helping them in predation .

Fins are paired , Gill slits are uncovered with an operculum , They have no air bladder , The sex is separate ( unisexual ) , Fertilization is internal .

Examples : Shark and Ray .

Vertebrates

Vertebrates

Class : Osteichthyes

Habitat : They live in salt or fresh water , Endoskeleton is bony , The body is covered by bony scales , The mouth is terminal at the anterior tip of the body , Fins are medial and paired .

Gill slits are covered with an operculum , They have air bladder helping them in swimming and floating , The sex is separate ( unisexual ) and fertilization is external .

Examples : Bolti and Bouri .

Class : amphibia

The body is covered with smooth slimy skin , They have four pentadactyl limbs , They are cold-blooded animals , The sexes are separate and fertilization is external , Such as Frog and Salamander .

Respiration : It takes place by several different ways according the stages of its growth as the following :

Embryonic stages : Breathe by gills because they live  in water , Adult stages : Breathe atmospheric air by lungs and skin because they live on land .

Frog croaking : It is a voice comes from male frogs during mating season  for attracting the females for mating , The male can produce this voice because it has a special structure called voice sac which does not found in females .

Class : Reptilia

The body consists of four regions : Head , neck , trunk and tail , It is covered with a dry skin with horny scales and may be supported by horny plates .

Limbs : They have four weak pentadactyl limbs and each toe ends with a horny claw , The limbs may be absent , So , some of them move by creeping .

Respiration : They respire atmospheric air by lungs , They are cold-blooded animals , Sexes are separate and fertilization is internal , The females lay eggs with calcareous or skiny shell on laud .

Examples : Crocodile , Tortoise , Gecko , Lizard , Chameleon and snake .

Class : Aves

The body is covered with feathers , They breathe by lungs , They are warm-blooded animals , Sexes are separate and fertilization is internal , The females lay eggs and incubate them till hatching .

They have four limbs : The anterior ones are modified into wings for flying , The posterior ones : each ends by four digits provided with horny claws , They are used for moving on ground ( ostrich ) , climbing ( sparrow ) , swimming ( duck ) and predating ( Hawk ) .

Appropriateness ( or adaptability ) of internal structure of birds for flying :

Their bones are hollow and light , The sternum is broad for attachment of the strong thoracic muscles which move wings during flying , Their bodies contain air sacs act as stores additional amounts of air during flying .

Examples : Sparrow , pigeon , Hawk , Duck , Chicken , Ostrich , Eagle .

Class : Mammalia

The body consists of four regions : head , neck , thorax and abdomen , It covers with skin that is covered with hair .

Limbs : They have four pentadactyl limbs , They provided with Claws , Nails , Hoofs or Pads .

Respiration : They respire atmospheric air by two lungs and they are warm blooded animals .

Teeth are dissimilar ( incisors , canines and molars ) , Sexes are separate , Fertilization is internal , The majority of females are viviparous and have mammary glands that secrete milk to suckle the youngs .

Class Mammalia is classified into three sub-classes , which are :

Sub-class : Prototheria

They do not give birth but they lay eggs and incubate them , The mother suckles its youngs with milk secreted from its mammary glands on its abdomen , They have a cloacal opening through which urine , faeces and eggs emerge , Such as Duck-billed platypus and Spiny ant-eater .

Sub-class : Metatheria

They give birth immature youngs , The mother suckles its youngs from nipples found inside a special pouch at the bottom of its abdomen where it keeps its youngs until they become fully grown , Such as Kangaroo .

Sub-class : Eutheria

They are placental mammals that give birth fully developed youngs , They mother suckle its youngs with milk secreted from its mammary glands .

Eutheria includes many animals that are headed by human and it is divided into many orders , the most important ones are Edentata , Insectivora , Carnivora , Perissodactyla , Artiodactyla , Cetacea , Rodentia , Lagomorpha , Chiroptera , Proboscida and Primates .

Orders , General characteristics of Eutheria and Modern technologies in classification of living organisms

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