1) characters of vertebrates biology.pptx

characters of vertebrates

1. VERTEBRATES

2. CHARACTERISTICS Members of vertebrates, within the phylum Chordata have , at some stage of life : 1- A notochord 2- a dorsal nerve cord: is a hollow tube above the notochord 3- pharyngeal pouches: are small out pockets of the anterior digestive tract . 4- A post anal tail: consists of muscle tissue and lies behind the posterior opening of the digestive tract. In most vertebrates, in the chordates phylum: the dorsal nerve cord develops into the brain and the spinal cord. The notochord is replaced by the backbone. In aquatic vertebrates, the pharyngeal pouches have evolved into gills for breathing. 2

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4. CHARACTERISTICS 4 Vertebrates have three characteristics that distinguish them from other chordates . First, vertebrates have vertebrae that surround the dorsal nerve cord and form the vertebral column. Second , vertebrates have a cranium , or skull, that protects the brain. Third , all vertebrates have an endoskeleton (an internal skeleton) composed of bone or cartilage.

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6. 6 Vertebrate Classes: Today , there are about 45,000 species of vertebrates. The nine classes of vertebrates are: 1 • Hagfishes (class Myxini ): The notochord remains throughout life. Hagfishes do not have vertebrae. Many scientists do not consider them vertebrates. They are included with vertebrates because they do have a cranium and an endoskeleton

7. 7 Vertebrate Classes 2 • Lampreys (class Cephalospidomorphi): unlike hagfishes, lampreys have a primitive vertebral column composed of cartilage that surrounds the notochord.

8. 8 Vertebrate Classes 3 • Sharks, Rays, Skates, and Ratfishes (class Chondrichthyes ): These predatory fishes have jaws and paired fins. Their skeleton is made of cartilage, not bone .

9. 9 Vertebrate Classes 4 • Ray-finned Fishes (class Actinopterygii ): All have jaws and paired fins, most have a skeleton composed of bone. These fish have fins supported by rays of bone that fan out from a central bony axis.

10. 10 Vertebrate Classes 5 • Lobe-finned Fishes (class Sarcopterygii ): Extinct lobe-finned fishes are thought to be the ancestors of amphibians.

11. 11 Vertebrate Classes 6 • Amphibians (class Amphibia)— About 4,880 species of frogs, toads, and salamanders belong to this group. Their skin is thin and is permeable to gases and water. Most species lay their eggs in water and pass through an aquatic larval stage.

12. 12 Vertebrate Classes 7 • Reptiles (class Reptilia ): This group includes turtles, crocodiles, alligators, lizards, and snakes. The skin of reptiles is dry and scaly. There are about 8,000 species.

13. 13 Vertebrate Classes 8 • Birds (class Aves): Birds are characterized by adaptations that enable flight, including feathers, hollow bones, and a unique respiratory system. There are over 10,000 species.

14. 14 Vertebrate Classes 9 • Mammals (class Mammalia): All mammals have hair and nurse their young with milk. There are about 4,400 species.