2Characteristics of Amphibians VertebrateLives in water as larva; land as adult (some exceptions)Breathes with lungs as adultMoist skin with mucus glandsNo scales and claws
3Evolution of Amphibians First amphibians during Devonian PeriodTransitioned from water to landBreathe airProtect eggs and themselves from drying outSupport against the pull of gravity
4Evolution Continued…Adaptations evolved to live at least part of life out of water.Stronger bones in limbs and limb girdles; more efficient movementLungs and breathing tubesSternum or breastbone for shield and support.
5LungsPelvic GirdleLeg Bones: The legs of a land vertebrate must be strong enough to hold its weight.Skin: The skin and the lining of the mouth cavity of many adult amphibians are thin and richly supplied with blood vessels. Watery mucus is secreted by glands in the skin.
6As Adults lungs are richly supplied with blood vessels and folds that increase surface area
7Class Amphibia Includes frogs, toads, salamanders, and caecilians. Small and diverse classDue to extinction of most amphibians during Permian Period (climate changes)Low, swampy habitats disappeared
8Feeding Tadpoles Adults Filter feeders or herbivores (algae) Intestine breaks down hard plant materialAdultsCarnivoresSticky tongues to capture insects
9Respiration Gas exchange through skin and gills (larval stage) Lungs, skin, and lining of mouth cavity (adult stage)Lungless amphibians: thin lining of mouth cavity and skin
10Circulation Double loop First loop Oxygen-poor blood from heart to lungs and skinOxygen-rich blood from lungs and skin to left atriumSecond loopOxygen-rich blood from heart to rest of bodyOxygen-poor blood from body back to heart
11Amphibian Heart Three separate chambers Left atrium Right atrium To body, lungs and skinFrom BodyFrom LungsThree separate chambersLeft atriumRight atriumVentricleRight atriumLeft atriumVentricle
12Excretion Kidneys to filter wastes from blood Urine excreted; travels from ureters to cloaca to outside or stored in urinary bladderHeartLungKidneyUreterUrinary bladderCloaca
13ReproductionFemales lay eggs in water; male fertilizes them externally (most amphibians)Internal fertilization (salamanders)After fertilization; frog eggs encased in sticky, transparent jellyYolk of egg nourishes embryo
14Movement Wiggle tails; flattened tails for propulsion (larva) Adult salamanders walk or runFrogs and toads: well developed hind limbs (jump long distances)
15Response Well developed nervous and sensory systems Nictitating MembraneMoist and transparentLocated inside regular eyelidCan be closed over the eyeTympanic MembraneEardrums located on each sideLateral LineUsed to detect movement in water
17Frog DigestionFood enters the mouth esophagus stomach small intestine large intestine cloacaCloaca: muscular cavity where solid waste, urine, eggs and sperm exit bodyLiver, pancreas and gall bladder excrete enzymes that aid in digestionFrog Movie
19Frog Reproduction Adults ready to breed in 1 to 2 years Eggs laid in water (external fertilization)Fertilized eggs tadpoles (several days to few weeks)Tadpoles gradually lose tails and gills, grow limbs.