1. Subphylum Vertebrata Phylum Chordata

2.  The remaining vertebrates form a clade called the superclass Tetrapoda  Amphibians and Amniotes (including nonavian reptiles, birds, and mammals) are the two major extant branches of tetrapod phylogeny

3.  Life originated in water.  Nevertheless, organisms invaded land, carrying their watery composition with them  Vascular plants, snails and arthropods made this transition much earlier than vertebrates, thus generating a food supply that early terrestrial vertebrates would eventually use.

4.  Importance physical differences that animals must accommodate when moving from water to land 1.Oxygen content 2.Density 3.Temperature regulation 4.Habitat diversity  Terrestrial animals can obtain oxygen far more easily than aquatic ones, however, air has approximately 1000 times less buoyant density than water thus providing little support against gravity requiring animals to develop strong limbs and remodel their skeleton.

5.  Lungs  Legs for walking (hopping) on land ◦ See 25.2 pg 546 ◦ One could recognize the humorous, radius, ulna as well as other wrist bones  First tetrapods (amphibians)  Thin skin

6.  Skeleton mostly boney ◦ Ribs present in some  4 limbs (2 pairs - usually) ◦ Some may have one pair, some have none  Respiration by skin and lungs  Vision in air ◦ Cornea rather than lens ◦ Eyelids and lachrymal glands (protect and wash eyes)  Eardrum for transmitting vibrations to inner ear  Mouth is large with small teeth  Internal nostrils  10 pairs of cranial nerves  Separate genders

7.  Most are either aquatic OR terrestrial throughout their life  Some can be metamorphic ◦ Larvae - aquatic, Adult form – terrestrial  Salamander - metamorphic ◦ Internal fertilization ◦ Receives a packet of sperm (spermatophore) left by male on a leaf or stick ◦ Lay eggs in masses ◦ Larvae hatch with external gills and a finlike tail

8.  Terrestrial species have direct development ◦ Miniature versions of their adult parents  American newts ◦ Complex life cycles ◦ Aquatic larvae metamorphose into terrestrial juveniles that later metamporphose again to produce secondary aquatic breeding adults ◦ Many newts will skip the terrestrial stage, remaining completely aquatic

9. Evolution

10.  Phylum Chordata ◦ Superclass Tetrapoda  Class Amphibian  Order Gymnophiona  Order Urodela  Order Anura

11.  “gymnos”- naked ; “opineos”- of a snake  Elongate, limbless, burrowing creatures called caecilians  Live primarily in South America, also found in Africa, India and Southeast Asia  Long slender body  Small dermal scales  Long ribs

12.  Many vertebrae  Eyes are small (most species blind as adults)  Food consists of worms and small invertebrates  Fertilization is internal, and males have a protrusible copulatory organs ◦ Eggs deposited in moist ground near water ◦ Embryos eat wall of the oviduct for nourishment

13.  “Oura”- tail; “delos”- evident  Tailed amphibians – salamander  Found in northern temperate regions of the world, most abundant in North America  Small, most less than 15 cm long ◦ Some aquatic salamanders can be quite large, up to 1.5m in length  4 limbs

14.  Carnivorous ◦ Feed on worms, small molluscs, and small arthropods  Life styles ◦ Metamorphic  Respiration by lungs, external gills and skin ◦ Have gills as larve, loose them as adults

15.  Mud puppies  Live on the bottoms of ponds and lakes  Permanently gilled  Do not metamorphose

16.  May remain permanently gilled, or, should its pond habitat evaporate, metamorphose to a terrestrial form that loses its gills and breaths by lungs

17.  “an”- without; “aura”- tail  Frogs and toads  Their aquatic mode of reproduction and water- permeable skins prevent them from wandering too far away from sources of water  No tails ◦ Larval stages have tails, adult forms do not  Legs adapted for jumping  Skin is thick and moist

18.  Eggs hatch into tadpoles ◦ Long finned tails ◦ Both internal and external gills ◦ No legs ◦ Specialized parts for herbivorous eating

19.  Goliath Frog  Can measure up to 13 inches long  Eats rats and ducks

20.  Eleutherodactylus iberia  Smallest frog