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Class Amphibia MOVEMENT ONTO LAND. Class Amphibia MOVEMENT ONTO LAND. In order for animals to live on land they: need to support their own weight (i.e., deal with gravity) Water more dense and also property of buoyancy

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class amphibia movement onto land3
Class Amphibia MOVEMENT ONTO LAND
  • In order for animals to live on land they:
  • need to support their own weight (i.e., deal with gravity)
  • Water more dense and also property of buoyancy
  • because of this skeletal and muscular systems of terrestrial organisms have to be better developed.
class amphibia movement onto land4
Class Amphibia MOVEMENT ONTO LAND
  • In order for animals to live on land they:
  • Resist drying
  • a constant problem in daily life
  • rate of evaporation in most terrestrial systems very great
  • resistance to drying is especially important during reproductive stages (i.e., egg) since they can not do anything actively to prevent water loss
class amphibia movement onto land5
Class Amphibia MOVEMENT ONTO LAND
  • In order for animals to live on land they:
  • deal with rapid temperature changes
      • daily and seasonal changes in water environment less than in the air
  • be able to extract oxygen from air
      • oxygen 20 times more abundant in air than water
amphibian early evolution
Amphibian Early Evolution
  • Amphibian ancestors: Devonian (400 million years ago)
    • Sarcopterygii (lobe-finned fishes)
      • had rudimentary appendages
      • had lungs - could be used used to breathe air
  • during Carboniferous (350 million years ago)- was good environment for amphibian development
    • characterized by wet warm environments
    • lots of swampy areas
    • during this time amphibians had their greatest rate of evolution
slide7

Fish-like appendage

More like modern amphibians

amphibian evolution
Amphibian Evolution
  • Amphibians have met challenge of land only half way
  • still very tied to water

skin has to be kept wet at all times

      • many use skin to aid in respiration
    • all amphibians are tied to water to reproduce
      • almost all lay eggs in water and larval stages are aquatic
amphibians characteristics adults
Amphibianscharacteristics - adults
  • Upper jaw fused to skull
amphibians characteristics adults10
Amphibianscharacteristics - adults
  • with a three chambered (ventricle and two atria)
amphibians characteristics adults11
Amphibianscharacteristics - adults
  • respiration more efficient
  • respiration through gills (in some), lungs, skin
amphibians characteristics adults12
Amphibianscharacteristics - adults
  • Skin:
    • no scales; skin smooth, moist with many glands
    • epidermis with keratin, below is dermis
    • skin color due to chromatophores located in dermis;
amphibians characteristics adults14
Amphibianscharacteristics - adults
  • Nervous System
    • 10 pairs of cranial nerves
amphibia reproduction
AmphibiaReproduction
  • are dioecious;
  • copulation is called amplexus,
    • fertilization mostly external in frogs and toads and internal in salamanders;
    • mostly oviparous, some ovoviviparous some viviparous; with development of larva (tadpole
amphibia adult characteristics
Amphibia AdultCharacteristics
  • limbs - four (tetrapod); some are legless
  • nostrils open into anterior part of mouth cavity
  • many (i.e., frogs) have developed vocal chords to produce sounds for mating
amphibia larval characteristics
AmphibiaLarval Characteristics
  • fish-like
    • finned tail
    • lateral line system as in fishes
    • 3 pairs of gills
    • 3 pairs of aortic arches
    • no lungs in early stages
slide22

Amphibia

Larval Characteristics

  • two chambered heart
  • no limbs in early development
  • some show neotony
    • reach sexual maturity,
    • while retaining gills and other larval characteristics;
    • most commonly seen in salamanders
    • some are permanent "larvae"- called obligatory neotony (ex mud puppy- Necturus)
amphibia survey of classes
AmphibiaSurvey of Classes
  • Gymnophonia- (=Apoda); caecilians
    • very primitive
    • up to 200 vertebrae
    • limbs and girdles absent
    • pantropical; 160 spec
amphibia survey of classes24
AmphibiaSurvey of Classes
  • Caudata (=Urodella); salamanders
    • tailed
    • larvae resemble adults
    • some aquatic, some fully terrestrial
    • two pairs of equal limbs
    • 10-60 vertebrae
    • no vocal chords
    • holarctic; 350 species
amphibia survey of classes25
AmphibiaSurvey of Classes
  • Anura (=Salientia); frogs and toads
    • larvae and adults very different
    • adults tailless
    • hind limbs modified for jumping
    • 6-10 vertebrae
    • larvae aquatic; adults more terrestrial, especially toads
    • no gills as adults
    • have nictating membrane - prevent dessication of eye
    • have vocal cords
    • cosmopolitan; 3400 species