Slide 1 Subphylum Vertebrata includes all of the animals that we refer to as the vertebrates. The animals in this subphylum have pronounced cephalization, a vertebral column (also known as an axial endoskeleton), and a hard cranium that protects the brain.
Slide 2 Subphylum Vertebrata includes the fishes - the jawless fishes, the sharks and rays, and the bony fishes. It also include the amphibians, reptiles, birds, and mammals. Similar to the evolution of the plants - the story of vertebrate evolution is a story of increasing independence from water. The fishes are obviously all aquatic - the amphibians are more independent of water but still require a moist environment. The reptiles, birds, and mammals are charactertized by much reduced dependence on water.
Slide 3 The fishes include the jawless fishes - so called because they do not have a jaw and instead of sucker-like mouthparts. The Condrichthyes are also known as the cartilagenous fishes - their skeleton is made of cartilage. This group includes the sharks, skates, and rays. The Osteichthyes are also known as the bony fishes because their skeleton is made of bone. This is the largest most successful group of fishes and includes most of the freshwater fishes.
Slide 4 The jawless fishes are also known as the agnathans. They do not have jaws and instead of sucking and rasping mouthparts that many of them use to parasitize other fish. Sea lamprey for example use their sucking mouthparts to attach to lake trout and can ultimately kill the trout.
Slide 5 The other two groups of fish have jaws and paired fins. The fins help them to swim and steer more effectively while the jaws help them to grasp prey.
Slide 6 The Condricthyes includes the skates and rays.
Slide 7 And the Osteicthyes includes a huge array of fish with different body plans.
Slide 8 The amphibians evolved from a fleshy finned fish such as a lungfish or a coelacanth. The amphibians are the first land vertebrates but they are not completely independent of water. Just as plants had to overcome the obstacles of land - so did the animals. Land animals had to adjust their locomotion - this was accomplished by the development of four limbs (the land vertebrates are also called the tetrapods). Gills had to give way to lungs and skin for respiration. Most amphibians live in moist areas to prevent desiccation while reproduction became internal for many tetrapods.
Slide 9 The amphibians inlcude frogs, toads, and salamanders. You can see the moist skin of the amphibians - they are not completely independent of water.
Slide 10 The reptiles, birds and mammals are referred to as the amniotes. This is because all 3 groups reproduce via an amniotic egg. The amniotic egg provides protection to the developing embryo from drying out and also provides a nutrient supply. In this way the amniotic egg is similar to the seed of the seed plants - it allows an increased independence from water. The amniotes also have skaly skin which provides further protection from desiccation for the adult animals.
Slide 11 This image shows the amniotic egg in both a bird and a human. Bird eggs do most of their development outside the mother's body while the human egg develops internally.
Slide 12 Reptiles include lizards, snakes, alligators and turtles. Some reptiles have returned to the water and live an aquatic life. They retain terrestrial characteristics such as lungs.
Slide 13 Birds arose from the dinosaurs and are characterized by feathers made of keratin and flight. Feathers most likely evolved for insulation and then secondarily became important for flight. Flight requires a light body plan - and birds have evolved to have a very light body. Birds' bones are hollow to lighten the skeleton and many of the birds organs have been reduced to reduce weight. For example, most tetrapods have two ovaries but birds only have one.
Slide 14 Once birds evolved, diversification took place rapidly and we see a great diversity in the birds.
Slide 15 Our last group of vertebrates are the mammals. Mammals evolved from a reptilian ancestor and are characterized by a modified skeleton - particularly the structure of the lower jaw and the inner ear. Mammals have fur (another modification of keratin) and fur provides insulation for endothermic or warm-blooded animals. Mammals are also characterized by the presence of some sort of mammary gland which produces milk for offspring. The mammals contribute a lot of energy to parental care of young. Most mammals have live young but there is one group - the monotremes - that lay eggs. The marsupials are those mammals that give birth to undeveloped young and then raise these young in a pouch. The eutherians or placental mammals are the most successful and they give birth to more well-developed offspring.
Slide 16 The monotremes are now restricted to Australia and New Guinea but were once more abundant. They are egg laying mammals and include the duck-billed platapus and the spiny echidnas. Slide 17 The marsupials are the pouched mammals like kangaroos and koalas. They are found mainly in Australia but we have one prominent marsupial in the Americas - the opposum. Slide 18 The Eutherian or Placental mammals are the most successful group of mammals and are found world-wide. Placental mammals, which includes ourselves, give birth to well-developed offspring and invest a large amount of energy in parental care.