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Class Amphibia – Focus on the Mudpuppy

Class Amphibia – Focus on the Mudpuppy. Vertebrate Anatomy. Chordate Lineage Leading to Amphibians. The evolutionary path that leads to the amphibians is also closely related to the taxonomy that we assign amphibians

JasminFlorian
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Class Amphibia – Focus on the Mudpuppy

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  1. Class Amphibia – Focus on the Mudpuppy Vertebrate Anatomy

  2. Chordate Lineage Leading to Amphibians • The evolutionary path that leads to the amphibians is also closely related to the taxonomy that we assign amphibians • The best classification/taxonomy does reflect evolutionary history of organisms

  3. Kingdom Animalia • All animals (even the most primitive) possess certain characteristics • Eukaryotic cells • No cell walls • heterotrophic • Some ancient member of the animal kingdom gave rise to…

  4. Phylum Chordata • All chordates possess the characteristics found in all animals, PLUS • Dorsal hollow nerve cord • Notochord • Pharyngeal gill slits • Post anal tail • Some ancient Chordate gave rise to…

  5. Subphylum Vertebrata • All vertebrates possess the characteristics found in all animals and in all chordates, PLUS • A backbone • Note that no animals up to and including this INITIAL vertebrate had jaws… • Some ancient vertebrate then gave rise to…

  6. Superclass Gnathostomata • All gnathostomes possess all the characteristics found in all animals, all chordates AND in all vertebrates PLUS • Jaws • Some ancient gnathostome then gave rise to…

  7. Classes Chondrichthyes and Osteichthyes • The first gnathostome that arose was most likely a bony fish (osteichthyes). It is thought that sharks (chondrichthyes) arose from an extinct group of bony fish (placoderms) and that their cartilaginous skeletons are a later development. • At any rate, the chondrichthyes line, though quite successful (there are lots of sharks, skates and rays) is a “dead end” in that it does not give rise to any higher vertebrates • The bony fish have two very important subclasse. These are…

  8. Subclass Actinopterygii and Subclass Sarcopterygii • The Actinopterygii you learned about when we did the perch. These are the ray-finned fish • This is a hugely important group as it includes the vast number of bony fish HOWEVER… • It is NOT the group of bony fish that gave rise to the amphibians • The Sarcopterygii is a very important group • NOT because it has lots of members – actually few • It is thought that some member within this group gave rise to amphibians (and thus ALL tetrapods)

  9. The important characteristic of this group is their fleshy-fins Their fins are thick and fleshy, not thin like those of the ray-finned fish It is this group of fish that is believed to have given rise to the amphibians Their limbs were substantial and muscular enough to act like very primitive “legs” allowing the first amphibian-like ancestors to “walk/crawl” over short spans of land Presumably to escape predators in the water and/or move from one small pool to another to exploit food resources Subclass Sarcopterygii

  10. Class Amphibia • At this point, we discuss all vertebrates (those arising beyond the fishes) as tetrapods • Means 4 limbs • These are the LAND vertebrates • So… the vertebrate group basically consists of two major groups (note that these are NOT formal levels of classification) • Fishes – water dwelling • Tetrapods – land dwelling (mostly)

  11. What are the advantages of land living? • Less competition for food and other resources (at least at first) • Escape predators chasing you in the water • Not near as many predators on land (at least at first) • Lots of unexploited resources on land (at least at first)

  12. Problems aquatic animals had to overcome in order to live on land • Movement on land • Breathing • Water loss from tissues • Reproduction • Get sperm to egg • Prevent drying of fertilized eggs and embryos • Energy • It takes more energy to move on land • It takes more energy to maintain body temperature on land because temperatures are less stable on land

  13. Even though amphibians can live on land, the transition is incomplete… • Most amphibians have external fertilization and development • Skin must be kept moist because it is used as a breathing organ • Thus drying of tissues is still a problem • Though lungs are found in most adults, gills are still present in juvenile forms.

  14. Generalized Characteristics of Amphibians • Aquatic as juveniles; terrestrial as adults • Of course there are always exceptions • Aquatic characteristics • Gills • Lateral line • Tail fin • No limbs • Algae eaters • Terrestrial Characteristics • 4 limbs (and no fins) • Lungs • carniverous

  15. The Amphibian Heart – an organ in transition • Amphibians possess a 3 chambered heart • 2 atria and 1 ventricle • Atria receive blood • Ventricle pumps blood

  16. The Amphibian Heart – an organ in transition • It is in this heart that we first see a “double loop” circulation pattern • Remember the single loop in fish • Drawback – blood slows down a LOT after passing through the capillary beds of the gills AND the body • In amphibians: • Blood is sent in one loop to the lungs/skin • Blood is sent in a second loop to the organs of the body • Efficiency of the double loop • After going to the lungs/skin (or gills) the blood is returned to the heart for another PUMP • THEN the blood goes off the the body • TWO pumping events prevent the blood from slowing down so much as it returns to the heart

  17. The Amphibian Heart – an organ in transition • Drawbacks of the amphibian heart • Separation of oxygenated blood coming from lungs/skin and deoxygenated blood coming from the body organs is INCOMPLETE • There is some MIXING of oxygenated and deoxygenated blood in the VENTRICLE • Thus making this circulatory arrangement NOT as efficient as would be ideal.

  18. The Mudpuppy Heart • We need to remember that the mudpuppy is a bit odd in that it’s lungs are essentially useless as respiratory organs, so the circulation path of the blood is not benefiting so much from oxygen from the lungs.

  19. Classification of Modern Amphibians – 3 Orders • Order Caudata – the salamanders • 4 limbs • Long tail (used for propulsion in swimming) • Crawling and/or swimming • Many actually have internal fertilization through the use of a spermatophore, but development is external • Neoteny in some (sexual maturity as juveniles)

  20. Classification of Modern Amphibians – 3 Orders • Order Anura – the frogs and toads • Jumping (adults) • No tails (except juveniles) • Both fertilization and development are external • COMPLETE metamorphosis

  21. Classification of Modern Amphibians – 3 Orders • Order Apoda – the “legless salamanders”

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