Amphibians Reptiles Mammals (not in this show) Vertebrates: Amphibians Reptiles Mammals (not in this show)

Overview: Half a Billion Years of Backbones By the end of the Cambrian period, some 540 million years ago An astonishing variety of animals inhabited Earth’s oceans One of these types of animals Gave rise to vertebrates, one of the most successful groups of animals

The animals called vertebrates include the groups: fish, amphibian, reptiles, birds & mammals Get their name from vertebrae, the series of bones that make up the backbone

The Origin of Tetrapods In one lineage of lobe-fined fish: The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life Tetrapod limb skeleton Bones supporting gills Figure 34.19

Amniotes Amphibians Greerpeton Hynerpeton lchthyostega Acanthostega Metaxygnathus Elginerpeton Eusthenopteron Panderichthys Lungfishes Coelacanths Ray-finned fishes Paleozoic Silurian Devonian Carboniferous Permian To present 420 415 400 385 370 355 340 325 310 295 280 265 Millions of years ago

Amphibians & Reptiles: Eukaryotic: Multicelullar Heterotrophic Animals (so they can move on their own) Have an Endoskeleton: skeleton is inside the body. Opposite case with: Insects, Arachnids, Scorpions: Exoskeleton (No bones, just hardened outer tissues)

Amphibians & Reptiles: Both are Ectotherms (opposite is endotherms like mammals) Ectothermic (“outside heat”) they depend on external sources of heat to help keep their body temperature up Means that: Body Temp Environment COLD HOT ECTO ENDO Amphibians & Reptiles have a slower Metabolism than mammals: So they can go longer w/o Food (weeks in some cases)

Amphibians: (frogs, toads, salamanders, newts) always live near water* Have thin slimy skin that dries very fast & must be kept moist or they can easily die of dehydration Lay their eggs in or near water sources Some spend their entire life or part of it, in the water (tadpoles)

Eggs Amphibian Reproduction: Their eggs lack the classic white shell of typical eggs. Since the eggs are usually placed in water: There is no need to prevent water loss OR to stand out (visually) to predators by dressing the egg up in shell Eggs

(e) American alligator (Alligator mississipiensis) Reptiles : bodies evolved for Water Conservation Evolved thick scales around their bodies Provided physical protection Stopped water loss (but can still absorb heat from outside) Body size can now be bigger w/o losing water (amphibians never over 150lbs  more surface area = more water loss) (e) American alligator (Alligator mississipiensis)

Overall Reptiles are adapted to be able to survive farther away from sources of water than most amphibians can. No scales or claws

Reptiles: Evolved behaviors to get or maintain body heat: Sunbathing (prefer rocks) Dormant in Winter or… Live where it is always hot (Tropics, Deserts) No reptile or amphibians live at top of High Mountains or in Extreme Cold Climates like the Artic, Antarctic or Tundra (b) Australian thorny devil lizard (Moloch horridus)

Reptile Reproduction: Reptilian eggs have a strong leathery shell to protect the young and prevent dehydration They will tear, but won’t crack like bird eggs Most reptiles provide no parental care other than leaving the eggs in a safe spot (female crocs & possibly dinosaurs are exceptions) Most reptiles lay 4 or more eggs at a time

Reptiles (that have legs) can lift their bodies off the ground Movement Heart anatomy Being on land demands a lot more energy, so heart size and efficiency needs to increase to bring more O2 to body Most amphibians will drag their stomachs when they “walk” or jump 2 chamber heart: Fish 3 chamber hearts Amphibians Most Reptiles 4 chamber hearts Some reptiles Birds (flight) Mammals Reptiles (that have legs) can lift their bodies off the ground

Reptiles: the original large land carnivores The majority of living reptiles are carnivores (only reptiles have claws, no amphibian has claws) Some turtles and a few lizards are the only reptilian herbivores Reptilian herbivores may have teeth that are flatter or no true teeth at all

Reptilian Carnivores generally can’t shear or chew their food like mammals can, so they will either try to tear or rip it apart (croc “death-roll”) or will try swallow food whole (snakes)

Venom and Toxin Use Snake Skull