1. Amphibians
1st tetrapods

2. Classification Kingdom – Animalia Phylum - Chordata Class Amphibia
3 Orders
Anura (Frogs & Toads)
Caudata(Salamanders)
Gymnophiona(Caecilians)

4. Movement onto Land
Life began in the water, animals are made of mostly water, and all cellular functions occur in water.
Invasion onto land required modification of almost every system in the vertebrate body. The Amphibian is an example of this terrestrial transition.
They are tetrapods-presence of 4 muscular limbs and feet with toes and fingers

5. Accommodations to be considered when moving to land
Oxygen content
Oxygen diffuses more readily in air then water
20 times more oxygen per unit volume in air
Development of lungs
Terrestrial animals use much less energy acquiring air
Support
Provides little support against gravity
Requires the development of strong skeleton and muscular limbs to get around
Lighter skull w/jaw that can crush prey held in mouth
Body wall musculature is reduced, unlike in the fish…think of eating fish compared to frog legs.

6. Accommodations to be considered when moving to land
Temperature regulation
Air fluctuates in temperature more then water
Amphibians are ectothermic-depend on external heat sources to regulate body temp
Requires (mainly) behavioral and physiological strategies to protect themselves from thermal extremes
Habitat diversity
Diverse biomes to live in and adjust to
Found on all continents except Antarctica and absent from some oceanic islands
Often bask after a meal to increase rate of metabolic reactions. Often have a pretty wide temperature tolerances.

10. Characteristics Ectothermic 3-chambered heart (Double circulation)
Smooth skin, lacks scales (Desiccation if dry)
Cutaneous respiration
Lungs (Positive pressure mouth breathing)
Excretes urea
Lack claws on toes

11. Characteristics of Class: Amphibia—on both sides
Over 5,000 species
Require a metamorphosis from water to land during development
Skin is thin and requires moisture
Ectothermic—body temperature varies with outside changing temperature (cold blooded)
Eggs lack multicellular membranes or shells, usually externally fertilized and laid in water

12. Order Gymnophiona “caecilians”
Limbless (naked snake)
Tropical forests of South America, Africa, and South East Asia
Most species totally blind
Mostly burrow or aquatic
Carnivores
All thought to have internal fertilization
Some lay eggs (female guards), others develop inside female

13. Gymnophiona
Interesting meal!
Click
New caecilian: click pic

14. Order Caudata “salamanders”
Having a tail
Some fully aquatic, fully terrestrial, or amphibious
Found in all North America, tropical areas of Central and northern south America
Carnivorous both as larva and adult
Some have no lungs (respire through skin), some keep gills

15. Caudata
Salamanders
Newts (Efts)
Mudpuppies
Sirens
Click
Axolotl

16. Spanish Ribbed Newt
adapted from

17. Click

18. Order Anura “frogs and toads”
Without tail
Carnivores (adults) and herbivores (larvae)
Some fully aquatic, fully terrestrial, or amphibious
Found in temperate and tropical regions throughout the world except New Zealand

19. Anura
Horror Frog

20. adapted from http://gideon. k12. mo

21. Body Plan Bilateral symmetry Skeleton mostly bony
Most have small teeth
Segmentation-head normally distinct from body
Four limbs (except caecilians)
Some have webbed feet
no nails or claws, 4-5 digits

22. Skin
Click:
Rain Frog
Made of Keratin a tough protein that helps protect against abrasions and water loss
Moist
Two layers—epidermis and dermis
With many glands
Granular glands- secretions are noxious or toxic to varying degrees from species to species
Some exhibit antibacterial, antifungal, and anticancer effects
Mucous glands waterproof the skin
Pigment cells—Chromatophores affect skin color and color changes

24. Respiration
Air is forced into the lungs with mouth muscles [positive pressure]
Air can be diffused through skin (cutaneous respiration) and the inside of the mouth (buccopharyngeal respiration)
The majority of carbon dioxide is released through the skin
Sound is created by forcing air over vocal cords and a large pair of sacs in the floor of the mouth

26. Circulation Closed system
Origin of the Systemic and Pulmonary Circuits
PULMONARY circulation- carries deoxygenated blood from heart to lungs and oxygenated blood back to heart
SYSTEMIC circulation-carries oxygenated blood from heart to body and deoxygenated blood back to heart
3 chambered heart
2 atria
1 ventricle
Spiral valve helps separate the flows of oxygenated vs deoxygenated blood

27. In amphibians, the blood makes two passes through the heart.
Heart ---> lungs --> heart ---> body

30. Nutrition
Click!
Carnivores feeding on insects, spiders, worms slugs, snails, millipedes
Bullfrogs may even feed on small mammals, birds, and other anurans
Many have a protrusive tongue is attached at the anterior/front of the mouth- with sticky secretions
Eyes are pushed down against roof of mouth to aid in swallowing

31. Digestion
Complete digestive system
Cloaca with vent (exit opening)

33. Excretion
Tadpoles excrete as AMMONIA through gills and kidneys like a fish
ADULTS: 2 KIDNEYS- remove nitrogen waste from blood and dilute with water to make urine Adults worry about drying out so excrete as UREA = less toxic than Ammonia & needs less water to dilute;
Urine flows through urinary ducts to CLOACA; URINARY BLADDER (pouch off cloaca) stores urine; BLADDER also stores water in dry periods (can reabsorb water from urine)

35. Nervous System DORSAL SPINAL CORD covered with bone (VERTEBRAE)
SENSES:
Smell—olfactory epithelium
EYES- important in hunting and avoiding predators; covered by transparent NICTITATING membrane
EARS- TYMPANIC MEMBRANE=eardrums on side of head; sound receptors in inner ear inside skull;
COLUMELLA-small bone transmits sound between tympanic membrane and inner ears

36. BRAIN covered by skull (CRANIUM), about same size as fish
MEDULLA OBLONGATA- controls autonomic body organs, relays info from body
CEREBELLUM-muscle coordination & balance
OPTIC LOBES- process info from eyes and other senses
CEREBRUM- higher thinking, learning, memory, reasoning, integrates behavior
OLFACTORY LOBES- for smell, larger than in fish

37. Reproduction Sexual with external fertilization
In the spring, male frogs and toads vocally attract females to mate with
Eggs are laid in large masses and can be anchored to vegetation, simply float in water, or laid under logs in moist ground
Packet of sperm may be left on vegetation and then inserted by the female herself
Male may force eggs to be evacuated from the female as he discharges his sperm over the eggs—amplexus

38. Amplexus- “firm embrace” Pseudocopulation

39. Frogspawn
Click!

40. Development
Eggs hatch into aquatic larva having external gills and tail (similar to fish)
Indirect development= Metamorphosis
Tadpoles
Frogs
Herbivorous
Carnivorous
Aquatic
Aquatic & Terrestrial
Single loop circulation
Double loop circulation
Gills
Lungs

43. Parental Care FYI
Overall, amphibians have a high fecundity and little or no parental care. Parental care has been reported for some species such as the gastric-brooding frog (Rheobatrachus silus) from Australia. Female of the gastric-brooding frog swallows the eggs after they are fertilized and they develop in her stomach. When fully developed into frogs, they are released through the female’s mouth.  The Strawberry Poison-dart frog (Oophaga pumilio) from Central America exhibits strong parental care as well. Once the eggs are laid, the male ensures that they are kept hydrated by transporting water. Then when eggs finally hatch into tadpoles, the female transport them on her back to suitable water-retaining location. 
Surinam Toad
Click pics for videos
Darwin’s Frog

45. Environmental Interaction
Require a somewhat cool environment
Most amphibians hibernate during winter months in soft mud of the bottoms of pools and streams
Some can tolerate freezing temperatures by making a type of antifreeze by accumulating glucose and glycerol in body fluids

46. Environmental Interaction
Are both predators and prey to others, for protection amphibians have developed
Poison glands
Urinate
Strong legs for leaping away
Biting at predators
Inflate lungs to avoid being swallowed
Camouflage

48. Aposematic- warning coloration

49. Toxic
Mimicry
Nontoxic

50. Frog Defenses

51. Yikes
Worldwide, populations of frogs have been decreasing and experiencing mutations.
Pollution, acid rain, ozone depletion, pesticides/chemicals, introduction of exotic predators, habitat destruction are a few contributing factors
Click pic for vid on Kihansi Spray Toad

52. http://www. amphibianark
-Big problem for amphibians!
Golden Frog (Panama)
Click: Part 1
Click: Part 2

53. Extinctions can be highly difficult to confirm due to the need of long term intensive field surveys. Using the most conservative approach to documenting extinctions, 34 amphibians are known to have vanished for ever since the year 1500 as a result of human activities. The majority of amphibian extinctions occurred during the last 100 years. However, the real number of extinct species is very likely to be an underestimate since amphibian inventories and monitoring are lacking in most parts of the world. Most scientists believe that more than 120 species are suspected to be extinct since the 1980s. Many of those “possibly extinct” amphibians have never been seen in the wild for decades!

54. Information from: http://www. endangeredspeciesinternational

55. Nearly one-third (32 %) of the world's amphibian species are known to be threatened or extinct, 43 % are known to not be threatened, and 25 % have insufficient data to determine their threat status.
As many as 159 amphibian species may already be extinct. At least 38 amphibian species are known to be Extinct; one is Extinct in the Wild; while at least another 120 species have not been found in recent years and are possibly extinct.
At least 42 % of all species are declining in population, indicating that the number of threatened species can be expected to rise in the future. In contrast, less than one percent of species show population increases.
The largest numbers of threatened species occur in Latin American countries such as Colombia (214), Mexico (211), and Ecuador (171). However, the highest levels of threat are in the Caribbean, where more than 80 % of amphibians are threatened or extinct in the Dominican Republic, Cuba, and Jamaica, and a staggering 92 % in Haiti.
Although habitat loss clearly poses the greatest threat to amphibians, a newly recognized fungal disease is seriously affecting an increasing number of species. Perhaps most disturbing, many species are declining for unknown reasons, complicating efforts to design and implement effective conservation strategies.
Info from:

56. Map of threatened species worldwide.

58. Bioindicators