Transcript Origin of Amphibians

Amphibians
Classification
 Phylum Chordata
 Subphylum Vertebrata
Class Amphibia
Order Urodela
Order Anura
Order Apoda
Origin of Amphibians
 Amphibia means “double life”
 ~4200 species
 Believed to evolved from early lobefinned fish over a million years ago.
 Advantages to land over water
 Large food supply
 More shelter
 No predators
General Characteristics
 Endoskeleton
 Ectothermic
 Depend on water for reproduction
 Must live around moist areas
 Thin moist skin
 Used for gas exchange
 Undergo metamorphosis
General Characteristics
 Respiration
 Lungs, skin, and some gills
 No Claws
 Tetrapods- 4 legs
 3-chambered heart
 1 chamber recieves oxygenated blood from lungs, 1
receives deoxygenated blood from body, 3rd
chamber pumps blood to body/lungs
Reproduction
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Separate sexes
Frogs and Toads- mostly external
Salamanders- mostly internal
Eggs laid- oviparity
Eggs develop inside without nourishment
from mother- oviviparity
 Eggs develop inside with nourishment
from the mother- viviparity
Metamorphosis
 Lifecycle
 Fertilized egg (laid in water) hatch into
tadpole
 Tadpole grows into adult frog/toad
 Fins are replaced with legs and 2chambered heart is replaced with a 3chambered heart.
Order Anura
Frogs and Toads
 No tail, neck, or scales
 Vocal chords found in larynx
 Males have pouches to increase volume of
call, used for attracting mates
 External Reproduction
 Specialized limbs for jumping
 Long sticky tongue attached to front of
mouth for catching prey
Frogs and Toads
 Adults have lungs
 Adults are carnivorous, tadpoles are
herbivores
 Tympanic Membrane (eardrum) picks up
vibrations from air and water.
 Eyes on top of head allow them to stay
submerged while seeing out of water
 Nictitating membrane- keeps eyes moist
Frogs vs. Toads
 Toads have
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Shorter legs
Larger bodies
Thicker skin with prominent warts
Live primarily on land
Prefer dryer climates
Causes of Decline
 5 reasons the populations of frogs and
toads are declining
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1. acid rain
2. water pollution
3. air pollution
4. use of pesticides
5. thinning ozone layer
Order Urodela
Salamanders
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Most abundant in North America
Have tails, no scales
4 equal limbs
Look like lizards, but with smooth, moist
skin and no claws
 Long slinder body
 Some are completely Aquatic
Salamanders
 Some breathe through skin while some
have lungs
 Carnivorous- feed on worms, small
arthropods, and small mollusks
 Internal Fertilization- Male deposits
spermatophore on leaf and female
recovers it and then lays fertilized eggs
Order Apoda
Rare Caecilians
 Long and Limbless
 Look like worms, but have eyes covered by skin
 Have small scales
 Short or no tail
 Some have small eyes, but most are totally
blind
 Found in tropical forests of S. America, Africa
and SE Asia
 Internal fertilization- some lay eggs, others
have live birth
Caecilian