Vertebrates

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Most amphibians have moist skin that complements the lungs in gas exchange.

Fertilization is external in most species, and the eggs require a moist environment.

Slide 30

Amphibians

(a) Order Urodela

(b) Order Anura

(c) Order Apoda

Slide 31

The “dual life” of a frog

(c) Mating adults

(a) Tadpole

(b) During

metamorphosis

Slide 32

Concept 34.6: Amniotes are tetrapods that have a terrestrially adapted egg

Amniotes are a group of tetrapods whose living members are the reptiles, including birds, and mammals.

Amniotes are named for the major derived character of the clade, the amniotic egg, which contains membranes that protect the embryo.

The extraembryonic membranes are the amnion, chorion, yolk sac, and allantois.

Amniotes have other terrestrial adaptations, such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs.

Slide 33

The amniotic egg

Yolk sac

Amniotic

cavity

with

amniotic

fluid

Chorion

Amnion

Albumen

Yolk

(nutrients)

Allantois

Embryo

Shell

Slide 34

Reptiles - lay shelled eggs on land

The reptile clade includes the tuataras, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs.

Reptiles have scales that create a waterproof barrier.

Most reptiles are ectothermic, absorbing external heat as the main source of body heat.

Birds are endothermic, capable of keeping the body warm through metabolism.

Slide 35

Hatching reptiles

Slide 36

Dinosaurs diversified into a vast range of shapes and sizes.

They included bipedal carnivores called theropods.

Paleontologists have discovered signs of parental care among dinosaurs.

Dinosaurs, with the exception of birds, became extinct by the end of the Cretaceous. Their extinction may have been partly caused by an asteroid.

Slide 37

Extant reptiles (other than birds).

(a) Tuatara (Sphenodon punctatus)

(c) Wagler’s pit viper

(Tropidolaemus wagleri)

(b) Australian thorny devil

lizard (Moloch horridus)

(e) American alligator

(Alligator mississippiensis)

(d) Eastern box turtle (Terrapene carolina carolina)

Slide 38