Amphibians

Vertebrates that are aquatic as larvae and terrestrial as adults, breathe with lungs as adults, have a moist skin that contains mucus glands, and lacks scales and claws Eggs have no shells, larvae are aquatic, respire through skin, evolved from lobe-finned fish (coelacanth), first vertebrate to colonize land Amphibians are tetrapods – animals with four feet (reptiles and mammals are also tetrapods )

Frog Anatomy

Feeding in Amphibians Larvae – filter feeders, herbivores, grow very quickly Adults – carnivorous Mouth – esophagus – stomach – small intestine – large intestine – and cloaca

Respiration in Amphibians Adults – lungs, mouth, and skin Larvae – skin or gills - tadpoles, salamander larvae, some adult salamanders have gills

Circulation in Amphibians Larvae have a two chambered heart; adults have a three chambered heart that pumps blood through a double-loop system Adults –Loop 1: Heart – lungs – heart –Loop 2: Body – heart Larvae –Single loop like fish: heart – gills – body - heart

Excretion in Amphibians Kidneys – send urine to cloaca or urinary bladder

Response in Amphibians Well-developed brain Hear and make sounds See well for hunting Evade predators by hiding, running away, toxic chemicals (poison arrow frogs)

Movement in Amphibians Larvae swim like fish Adults use their four limbs

Reproduction in Amphibians Females lay eggs in water and the male fertilizes them (external fertilization) – frogs and toads Sperm packet – salamanders Parental care – some carry larvae or eggs on back

Groups of Amphibians 2 major groups of Amphibians –Salamanders –Frogs and toads

Salamanders A few centimeters to 2 meters Some totally aquatic, others live both on land and in water Can regenerate lost limbs

Examples of Salamanders

Frogs and Toads Common Frogs more aquatic, toads more terrestrial Cannot regenerate lost limbs

The Life Cycle of a Frog Adult Frog Young Frog Fertilized Eggs Tadpoles Adults are typically ready to breed in about one to two years. Frog eggs are laid in water and undergo external fertilization. Frog eggs are laid in water and undergo external fertilization. The eggs hatch into tadpoles a few days to several weeks later. Tadpoles gradually grow limbs, lose their tails and gills, and become meat-eaters as they develop into terrestrial adults. Tadpoles gradually grow limbs, lose their tails and gills, and become meat-eaters as they develop into terrestrial adults.