Phylum Chordata:
Amphibians:
-
Herpetology
-Transition
-They have double life, land - water
-They are better adapted for land, but can't live without water.
-They are ectothermic.
-internal nostrils.
-Three chambered heart, pulmonary arteries & veins.
-Ear has tympanic membrane.
-eyelids & lacrimal glands.
-well adapted olfactory epithelium
-The olfactory & ear were improved for airborne odors & sounds
-ectothermic restrictions
Characteristics of modern Amphibians:
-many vertebrae & ribs present
-no notochord or exoskeleton.
-usually 4 legs with 4
or 5
digits
-skin is moist & have glands. no scales
-small teeth
-nostrils
-external gills in larval form & may persist thru life.
-heart has 3 chambers:
A. 2 atria &
B. one ventricle.
- pulmonary arteries & veins
-skin has is supplied with blood vessels
-Ten pairs of cranial nerves.
-sexes separate, fertilization mostly internal.
- metamorphosis happens in frogs
- mesolecithal
Caecilians: order Gymnophiona (Apoda)
-
South America, Africa, & South East Asia
-Elongated, limbless, burrowing creatures.
-eyes are small, most species are blind as adult.
-Internal fertilization viviparity can occur
- young eats wall of oviduct
-eat worms
Salamanders: order Caudata(urodela)
-having tail
-carnivorous both adult & larva
-Do not store glycogen & fat
-metamorphic: aquatic larvae & terrestrial adults
-Fertilization internally, direct development
-They may have external gills, lungs, both or neither of these.
- Mud puppies have perminant gills, eg. of
perennibranchiate
- Axolots lose their gills and develop lung when pond dries up
-Thyroxine
Frogs & Toads: order Anura (Salientia)
-Aquatic reproduction & water permeable skin.
-Tadpoles have internal & external gills
- no perennibranchiate
- no legs, finned tail, specialized mouth part for herbivorous feeding.
-Bullfrogs in farm have not been successful
-During winter month in temprate climate frogs hibernate
-Skin has 2 layers: epidermis & dermis
-All amphibians produce some type of skin poison
-drop for drop they are more poisonous than any other species.
-In the skin there are 3 types of chromatophores:
1.xanthophores, yellow, orange, red
2.iridophores; silvery, light-reflecting pigment
3.melanophores, black or brown melanin
-Amphibians have 3 sources of gas exchange- mouth, skin & lung.
- cutaneous breathing and buccal breathing
-carbon dioxide lost across the skin
- most of oxygen is taken up by lungs
-Both male & female frogs have vocal cords, but better developed in male.
-They are located in larynx or voice box
-closed circulation
-Double circulation: pulmonary & systemic circuits.
-Heart is a double pump - 2 atria & one ventricle
-circulation of Blood:
right atrium from all over the body ---> ventricle.
left atrium from the lungs oxygenated
---> ventricles.
ventricle pumps it to the rest of body
- ***spiral valve***
-Frogs are carnivorous.
-tongue glandular material to stick
-Short digestive tract
-The three fundamental parts of brain are:
1.forebrain: telencephalon sense of smell olfactory
2.midbrain: mesencephalon sense of vision
3.hindbrain: rhombencephalon sense of hearing & balance
-Brain of frog has 10 cranial nerves.
-Vision & Smell is the dominant sense
- while caecilians are blind
-Amphibian eyes at rest is adjusted for distant objects
- the lens is moved forward to focus on nearby objects
-eyes of bony fishes & lamprey is adjusted for near vision
- on distant object lens must moves backward.
-in amphibians upper lid of eye is fixed
- lower lid is transparent membrane which is movable.
-External fertilization, however as the female release the egg male release the sperm.
-6
to 9
days tadpoles hatch.
- breed, feed & grow during warm season
Evolutionary points:
-
life began in water
- animals are mostly made up water
- chemical Rxns happen in water
- Lack of water on land can cause problem
- problems on land:
A. oxygen
B. density
C. thermoregulation
D. different habitat
- advantages on land
-Plants & insects invaded land much earlier than vertebrates
-Birds & mammals are homeothermy
-aquatic vertebrate evolved 2 important features: lung & limbs
-Devonian period freshwater very unstable
-double circulation mechanism
A. systemic circulation
B. pulmonary circulation
-The vertebrate limb also evolved during Devonian period
-The Lissamphibians evolved during Carboniferous period to
A. the frogs (Anura),
B. Salamanders (Caudata) &
C. Caecilians (Apoda or Gymnophiona)