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  1. AMPHIBIANS Asma Thebo PH.D (CONT…) UNIVERSITY OF SINDH, JAMSHORO. The First Terrestrial Vertebrates 1
  2. GENERAL CHARACTERS OF AMPHIBIANS  Amphibians are cold blooded vertebrates which can hue on land and in water.  Amphibians show four limbs with which they can swim in water and jump or walk on the land, (But in apoda limbs are absent.)  In Amphibians animals exoskeleton is absent. But in apoda animals small cycloid scales are present.  In Amphibians the adult animals lungs are present. Gills are absent. But In some urodelans the gills are present.  Amphibians Skin is a respiratory organ.  The Amphibians skull is dicondylic.  Amphibians Ribs are absent.  In Amphibians The body divisible into head and trunk Tail is present in, urodela animals.  Amphibians Digestive system is well developed. A well developed liver Is present 2
  3. GENERAL CHARACTERS OF AMPHIBIANS  External ear is absent. Middle and inner ears are present, the middle ear columella auris Is present.  Amphibians Heart is 3 chambered with 2 auricles and 1 ventricle The blood contains R.B.C. They are nucleated. They contain hemoglobin.  Blood vascular system contain hepatic and renal portal systems.  Amphibians Kidneys are mesonephric. Urinary bladder is present. It stores urine.  Central nervous system is well developed. The brain occupies completely the cranial cavity. The brain is divided into fore, mid and hind brains. Brain continuous as spinal cord.  10 pairs of cranial nerves will arise.  Sexes are separate.  Male and female can be indentified - Sexual dimorphism.  In Amphibians the life history a larva stage may be present.  Amphibian Eggs are telolecithal, Cleavage is holoblastic unequal. 3
  4. Amphibians are animals that either move back and forth between water and land or live one of their stages of life in water and another on land. Amphibians are tetrapods“Four-foot” • The presence of four muscular limbs and feet with toes and fingers First amphibian: No one knows what the first amphibian was. The structure of limbs, skulls and teeth of lchthyostega are similar to the earliest amphibians. Two lineages of amphibians are formed in the late Devonian and early Carboniferous periods. These lineage can be differentiated by the structure of roof and the attachment of posterior portion of the skull to each other. Evolutionary Perspective • 4
  5. Amniotic lineage: One lineage of amphibians became extinct in the late Carboniferous period. An amniotic egg evolved in this group. It resisted dryness. This lineage is called the amniotic lineage. This lineage formed reptiles, birds; and mammals. 2. Nonamniote lineage: A second lineage flourished in the Jurassic period. Most of animals of lineage have become extinct. But some of them gave rise to the three orders of living amphibians. This lineage is called the nonamniote lineage. 5
  6. PHYLOGENETIC RELATIONSHIPS Fossil record provides evidence of many extinct taxa and no one knows what animal was the first stegocephalian. Taxonomists agree that amphibians are monophyletic and closely related to reptiles, birds, and mammals 6
  7. 01. ORDER CAUDATA This order consists of salamanders. Means “tail-bearing” Characteristics of order Caudata The 358 species belonging to the order Caudata can be generally divided into newts and salamanders. These animals are normally nocturnal and found in cool, shady habitats in the Northern Hemisphere. Some caudates are amphibious, others are entirely aquatic, yet others are entirely terrestrial and some burrow. Aquatic or burrowing species may have reduced or rudimentary limbs. 7
  8. Habitat: Caudates are restricted to damp or wet habitats because their skin acts as a respiratory organ through which oxygen enters the body. All are carnivorous Reproduction: Internal fertilization • Produce aquatic larvae • Larvae are similar to adults but smaller Newts Newts differ from salamanders in that adult newts are always terrestrial, returning to water only to breed in spring; larvae develop in water and then emerge onto land until mature and ready to breed in their turn. Salamanders have very diverse range of life cycles and many families are normally paedomorphic � adults retaining larval features, that may be more or less visible from the exterior. 01.ORDER CAUDATA 8
  9. 01. Order Caudata 9
  10. This order consists of caecilians. Means “naked like a snake” Characteristics of order Gymnophion Worm-like appear segmented because of skin folds that overlie separations between muscle bundles. Skin over eyes (most likely blind) Habitat: Burrow into the ground Reproduction: fertilization is internal. Can have aquatic larvae or embryotic larvae that develop on land. Young are miniature adults. Feeding: Eat soil and worms when they burrow. 02. ORDER GYMNOPHIONA 10
  11. 02. Order Gymnophiona 11
  12. This order consists of frogs and Toads. Means “without tail” Characteristics of order Anura About 4,000 species Long muscular hind limbs Webbed feet Habitat: Generally moist environments (can really be found almost anywhere) Reproduction: External fertilization • Undergoes metamorphosis from tadpole to adult Feeding: They mostly eat small insects and some plants. They utilize a sticky tongue, located on their lower jaw, that is extended from their mouth as a sort of sticky lasso to catch their prey. Most frogs sit and wait for their prey. Their skin colors and textures perfectly camouflages them in their surroundings. 03. ORDER ANURA 12
  13. 03. Order Anura 13