1. AMPHIBIANS

2. Diversity ◦ Ex: Frogs, salamanders, newts, and caecilians ◦ Amphibians are born without legs, and they grow legs as they develop (part of life cycle) ◦ Differ greatly in size  1 cm to 6 feet. ◦ Diet:  Carnivorous (eat only meat/other animals) or  Insectivorous -eat other organisms, especially insects.

3. Diversity, cont. ◦ About 5700 living species of amphibians.species ◦ The ancient amphibians were:  Typically larger in size  Contained massive teeth  Some had scaled skin ◦ Modern amphibians are:  Much smaller in stature/size  Have evolved a number of adaptations that are fit for whatever environment they live in

5. General Characteristics Ectothermal (cold-blooded) Life requirements: ◦ Require both land and water for survival  This is true for many amphibian species  However, others may be fully terrestrial, even being born on land (viviparity).  Others may only need a moist environment, not necessarily a pond or pool, while others may be completely aquatic (born in water, live in water)

6. General Characteristics Metamorphosis ◦ Go through life cycle changing event (from tadpole to adult)  All amphibians have a tadpole stage ◦ Most are biphasic  This means they go through an aquatic stage, and a terrestrial stage at some point

7. General Characteristics Metamorphosis ◦ The transition from aquatic to terrestrial must have many physical changes  Include:  absorption of the gills and tail  modified eyesight to see on land  thicker skin to cope with atmospheric environments  stronger limbs to support the weight of the body  a more cylindrical tail  new ways to catch food

8. General Characteristics Reproduction: Separate sexes Fertilization internal in salamanders/caecilians Fertilization mostly external in frogs/toads Mostly oviparous  Most produce shell-less (amniotic) eggs that are deposited in the water  These eggs rely on moisture from their surrounding water source,  Enclosed in protective, gelatin envelope  Nourished for very short time by mother

9. General Characteristics Reproduction, cont.: ◦ A typical biphasic species will return to the water a few years later (after it has matured and sexual maturity has been reached), ◦ Then, it will begin the lifecycle all over again with its own offspring.

10. General Characteristics Respiration: ◦ Can use lungs, skin and gills (either separately or in combo with one another) Salamander larvae possess external gills Frogs and toad larvae possess internal gills ◦ Usually two lungs (few exceptions) ◦ Often need moist surroundings to help breathe

11. General Characteristics Appendages/Limbs: Appendages/Limbs:  Most amphibians are tetrapods (four-legged) vertebrates  Some are legless  Webbed feet often present  No true nails or claws  Forelimb usually has four digits (sometimes five)

12. General Characteristics  Skin:  Amphibian skin is naked, lacking hair, feathers, or "true" scales Smooth and moist  Highly glandular with mucous glands  Some glands can be poisonous  May contain chromatophores (pigment cells)

13. General Characteristics ◦ Digestion:  Mouth usually large with small teeth (in both upper/lower jaws)  Two nostrils open into mouth cavity  Contain: stomach, small/large intestine, spleen, liver (two lobes), gallbladder, pancreas, cloaca and cloacal opening

14. General Characteristics ◦ Circulation:  Three-chambered heart  Contains two atria, one ventricle  Double circulation through heart  Skin is always supplied with blood vessels/oxygen

15. General Characteristics ◦ Excretion:  Cloaca—holding cell for the waste products  Paired mesonephric kidneys, bladder also present  Urea is main waste product ◦ Skeleton:  Most bony with varying numbers of vertebrae  Ribs present in most  Exoskeleton is absent  Vertebrates: have a backbone and many bonesbones

16. General Characteristics ◦ Body forms:  Vary greatly:  Options:  elongated trunk with a distinct head  compact, depressed body with fused head  Ex: salamander vs frog vs caecilian

17. General Characteristics ◦ Habitat:  The most abundant frogs are the 260 species of Rana found throughout temperate and tropical regions of the world  Frog species are often restricted to certain localities  Usually found near water  Amphibian populations are falling in most parts of the world  Winter: most amphibians will hibernate in soft mud in pools/streams

18. General Characteristics ◦ Biodiversity:  VERY good bioindicators of pollution, pH levels, oxygen levels and humidity  Can observe multiple mutations in frogs/salamanders  This helps to indicate high pollution/radiation levels

19. Classification ◦ The class Amphibia is comprised of three orders, Anura, Caudata, and Gymnophiona.  Anuran Biology –  Ex: Frogs and Toads  About 30 families and more than 4,500 species  Range in size from a few millimeters to a couple feet in length

20. Classification ◦ Anuran Biology, cont. –  Found in nearly every niche on Earth (very diverse group)  Presence of four limbs  hind limbs are typically larger and modified for leaping or climbing  Capable of vocalizing, and produce an array of sounds from squeaks to barking noises.  Most are external fertilizers.

21. Classification Caudate Biology (Order Urodela) – ◦ Ex: Salamanders, Newts, Sirens, Amphiuma, Waterdogs, and Mudpuppies ◦ Commonly referred to as the "tailed amphibians", a feature lacking in frogs and often overlooked in caecilians. ◦ 10 recognized salamander families, with a just more than 500 species. ◦ Typical have four limbs of similar size that are used for terrestrial walking.

22. Classification Caudate Biology, cont. (Order Urodela) – ◦ Typical have four limbs of similar size  Used for terrestrial walking. ◦ Some possess reduced limbs or lack limbs ◦ Incapable of vocalization ◦ Found in mostly temperate lands (although they have evolved to live elsewhere) ◦ Vary size a great deal, and include the largest amphibian in the world which can reach nearly 6 feet long.

23. Classification Caecilian Biology – (Order Apoda) ◦ Ex: Caecilians ◦ Long, segmented, worm-like amphibians, ◦ Very distinguishable because of body type/shape ◦ Some species are aquatic, and some are terrestrial ◦ The least studied amphibians, and definitely the most alien form.

24. Classification Caecilian Biology, cont. – (Order Apoda) ◦ Live underground and in aquatic habitats. ◦ Most species are found in tropical and subtropical environments in South America, Asia, and Africa. ◦ Lack appendages ◦ Have powerful heads and skulls for burrowing ◦ The only amphibians to possess dermal scales.