25.4 Amphibians AMPHIBIANS Sound

25.4 Amphibians KEY CONCEPT Amphibians evolved from lobe-finned fish. LINK Jointed limbs

25.4 Amphibians Amphibians were the first animals with four limbs and to be able to survive on LAND.

25.4 Amphibians First vertebrates to possess true tongues (moisten food) First with an outer layer of dead skin to be sloughed off First with true ears First with true voice box (frogs) First with a Jacobson's organ (chemosensory structure) Amphibian adaptations to live on land

25.4 Amphibians Amphibians return to the water to reproduce. Amphibian eggs are laid in water. The water is a great environment, it keeps them from drying out, supplies oxygen and removes waste. In fact, the Greek amphibios means having a double life (water and land)

25.4 Amphibians Not all eggs are laid in a typical pond however… Amphibians use many strategies to keep their eggs wet. –lay eggs directly in water –lay eggs on moist ground –wrap eggs in leaves –brood eggs in pockets on the female’s back LINK

25.4 Amphibians Why not completely terrestrial? Reproduction 3 chambered heart Inefficient lungs –Uses skin as accessory breathing organ –Skin must stay moist.

25.4 Amphibians Characteristics of Amphibians Ectothermic Moist, glandular skin w/o scales or true claws Three chambered heart Dependent on water to some degree Young are different from adult in structure and appearance (metamorphosis)

25.4 Amphibians adult frog young frog tadpoles fertilized eggs Tadpoles are aquatic larvae of frogs. During metamorphosis, tadpoles develop into their adult form. Not all amphibians undergo metamorphosis.

25.4 Amphibians Larva (tadpoles) have many “fish” characteristics Gills 2 chambered heart

25.4 Amphibians Modern amphibians can be divided into three groups. Salamanders (and newts) Caecilians Frogs (and toads)

25.4 Amphibians Salamanders Retain tail throughout life Two pairs of weak legs Distinct head/neck region There are over 300 species of salamanders.

25.4 Amphibians Caecilians are legless, burrowing, tropical amphibians. There are 160 species of caecilians. No limbs Minute eyes

25.4 Amphibians Frogs are the largest amphibian group and include toads. Lack a tail in the adult stage Head and trunk are fused Well developed legs There are over 3000 species of frogs.

25.4 Amphibians Difference between frogs and toads? All are in the same Order (Anurans) –Includes approx 20 families including the Ranidae (true frogs) and Bufonidae (true toads). –True toads lack teeth on their upper jaws –Fire bellied toads are frogs!

25.4 Amphibians Amphibians around the world are vanishing and may signal danger to our global ecosystem’s health One-third of all known amphibian species are threatened with extinction. The greatest threats are pollution and climate change, but disease, habitat destruction and fragmentation, and invasive species are also affecting amphibians. Amphibians feel the effects of environmental changes long before we do, partly because of their sensitive skin and watery way of life. Amphibians breathe partly through their skin—taking in vital oxygen. But the permeability that makes their skin special also makes amphibians sensitive to pollution in the soil, air, and water.

25.4 Amphibians Amphibians around the world are vanishing and may signal danger to our global ecosystem’s health