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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
  • 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
  • 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
  • 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

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
  • 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


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