1. Amphibians
Section 30.2

2. Animal Classification
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
Order Anura
Order Caudata
Order Apoda
Invertebrates
Animals
Fishes
Amphibians
Reptiles
Ectotherms
(cold-blooded)
Amphibians
Vertebrates
Phylum Chordata
Birds
Mammals
Endotherms
(warm-blooded)

3. What is an Amphibian? Class Amphibia – means “double life”
Starts life in water and changes on land
Evolutionary advantages over fishes
Thin, moist skin
Most amphibians have four legs
Lungs

4. What is an Amphibian?
Nearly all amphibians rely on water for reproduction
Undergo external fertilization
Water is needed to transport sperm

5. Ectotherms
Ectotherm – an animal that has a variable body temperature and gets its heat from external sources (can’t regulate their body temperature on their own)

6. Ectotherms
Amphibians become dormant in regions that are too hot or cold for part of the year
Many of them burrow into mud and stay there until suitable conditions return

7. Metamorphosis
Tadpoles possess fins, gills, and a two-chambered heart as seen in fish
Tadpoles develop legs, lungs, and a three-chambered heart to become adults

9. Metamorphosis
Young salamanders resemble adults, and they have gills and usually have a tail fin
Most adult salamanders lack gills and fins
Adult salamanders have no lungs and breathe only through their skin

10. Walking Requires More Energy
The evolution of the three-chambered heart in amphibians ensured that cells received the proper amount of oxygen

11. Walking Requires More Energy
One chamber receives oxygen-rich blood from the lungs and skin
Another chamber receives oxygen-poor blood from the body tissues
Blood from both chambers then moves to the third chamber which mixes the two types of blood

13. Walking Requires More Energy
Because of the mixture of blood, the skin is much more important than the lungs as an organ for gas exchange

14. Walking Requires More Energy
Because the skin of an amphibian must stay moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas

15. Frogs and Toads Frogs and toads belong to the order Anura
Frogs have long hind legs and smooth, moist skin
Toads have short legs and bumpy, thick, dry skin

16. Frogs and Toads
Adult frogs and toads are predators that eat invertebrates, such as insects and worms
Many species of frogs and toads secrete chemicals through their skin as a defense against predators
Frog eating bird

17. Frogs and Toads Frogs and toads also have vocal cords
Vocal cords – sound-producing bands of tissue in the throat
As air moves over the vocal cords, they vibrate and cause molecules in the air to vibrate

18. Frogs and Toads
Tympanic membrane – amplifies sounds frogs and toads make
Throat pouches and tympanic membranes increase the loudness of their calls

19. Frogs and Toads
Frogs and toads are among the first organisms to be exposed to pollutants in the air, on land, or in the water
Declining numbers of frogs species sometimes indicate the presence of pollutants in the environment

20. Salamanders
A salamander (order Caudata) has a long, slender body with a neck and tail
Salamanders resemble lizards, but have smooth, moist skin and lack claws

21. Salamanders
The young hatch from eggs, look like small salamander adults, and are carnivorous

22. Caecilians
Caecilians (order Apoda) are burrowing amphibians, have no limbs, and have a short (or no) tail
They are tropical animals with small eyes that often are blind

23. Caecilians
They eat earthworms and other invertebrates found in the soil
All caecilians have internal fertilization

24. Challenges of Life on Land
Some dangers living on land
1. Temperature of water remain fairly constant while air temperatures can vary greatly

25. Challenges of Life on Land
2. Without the support of water, the body was clumsy and heavy
The legs of a salamander are set at right angles to the body. This prevent the belly from dragging on the ground.

26. Challenges of Life on Land
Raised trunks from the ground increases mobility