Chapter 34 the origin and evolution of vertebrates 10 01 2015 Vertebrates one of the most successful of all animals Name from spine 52 000 species bilateral have coeloms deuterostome segmentation we are a tube in a tube FIGURE 34 2 Phylum Chordata 4 main characteristics that have to occur at some time in the animals life cycles keep track of when they happen o 1 Has pharyngeal gill slits pharyngeal clefts develop into slits suspension feeding structures in many chordates develop into parts of head and neck in human we have them as embryos o 2 Has notochord longitudinal flexible rod between digestive tube and nerve cord skeletal support throughout most of the length of a chordate some animals keep this throughout their whole life and others lose them but have residual remnants o 3 Has a muscular post anal tail blocks of muscle chevron like muscle segments used for swimming in some animals contains skeletal elements and muscles greatly reduced in embryonic development in many animals o 4 Dorsal hallow nerve chord single insects have ventral paired solid nerve cord going to develop into brain and spinal cord coelomate bilateral symmetry tube in tube 3 germ layers segmented body organs present Subphylum Cephalochordata o Lancelet common name o Blade like o Suspension feeders pharyngeal slits o Dorsal hollow nerve cord o Notochord o Segmentation o Tail o Has all 4 main characteristics of chordate o Spends most time buried with only mouth hanging out o Segmented muscles come form mesoderm somites blocks of segmented muscles found on each side of the animal Subphylum Urochordata o Tunicates seas squirts o More closely related to us than lancelets o Most resemble chordates during their larval stage which may last only a few minutes why it is related to us has all 4 o Adults are sessile sac like body o Only has pharyngeal slits as an adult o Filter feeders o Hox genes why it doesn t have a tail in adult stage o Manx gene responsible for getting rid of tail manx cat o Tunicates have fewer hox genes than other vertebrates o The genes associated with the heart and thyroid are common to all chordates o Genes associated with transmission of nerve impulse are unique to vertebrates Subphylum Craniata o Chordates that have a head o Includes the vertebrates back boned animals o Backbone replaces notochord o Have 2 clusters of hox genes lancelets tunicates only have 1 o Neural crest cells give rise to a variety of structures including some of the bones and cartilage of the skull o Migrating neural crest cells move around and become different things o Going to have at least 2 chambers in a heart have rbc with hemoglobin have kidneys GROUPING PISECES Gnathostomes have jaws that might have evolved from skeletal rods Genome duplication including duplication of Hox genes An enlarged forebrain associated with enhanced smell and vision In aquatic gnathostomes the lateral line system which is sensitive to vibrations Earliest in fossil record are extinct Also started seeing paired fins Devonian period age of the fish 360 mya Three lineages of jawed vertebrates today ray finned fish lobe fin fish Chondrichthyes cartilaginous o Class Myxini Hagfish Have a cartilaginous skeleton and axial rod of cartilage derived from the notochord but lack jaws and vertebrae Eat dead fish crawl in anus and eat flesh Slime glands secretes buckets of nasty slime to leave them alone Derived characteristic of Vertebrates Underwent a second gene duplication involving the Dix family of transcription factors Vertebrates have the following derived characters o Enclosing spinal chords o Elaborate skull o Finray the aquatic forms o Class o Class o Class Cephalispiomorphi Lampreys Represent the oldest living lineage of vertebrates They are jawless vertebrates Have cartilaginous skeleton different that that of cartilaginous fishes 2 chambered heart Placoderm Armored fish First mineralized structures that developed in our ancestors were in the teeth Then developed plates of bone All extinct now Chondrichthyes cartilaginous fish sharks Skeleton composed primarily of cartilage The largest and most diverse groups od chondrichthyans includes the sharks rays and skates Paedomorphis juvenile shapes found in babies and adults Sharks move to draw water over their gills Sleeping sharks can lay still on the ocean floor Osmoregulation all species have to regulate salt and water balance kidneys Creatures that live in freshwater have problem of water coming in where animals in salt water have a problem of water going out Sharks have really high levels of urea in bodies so they act like they are in freshwater Have very sharp vision but they can t detect color o Class Can detect electrical movement of muscles of fish Pectoral fins pelvic fins and dorsal fins Streamlined bodies and are swift swimmers Sharks have a short digestive tract a ridge called the spiral valve runs down whole tract to increase surface area Shark eggs are fertilized internally buy embryos can develop in different ways Oviparous eggs hatch outside the mother s body Ovoviviparous the embryo develops within the uterus and is nourished by the egg yolk Viviparous the embryo develops within the uterus and is nourished through a yolk sac placenta from the mother s blood The reproductive tracts excretory system and digestive tract empty into a common cloaca Osteichthyes Ray finned fish and Lobe fins Subclass Actinopterygii actin means ray catfish yellow fin tuna red lionfish common sea horse moray eel Freshwater and saltwater Spiked bone fins Operculum flaps over gills that protect them Fishes control their buoyancy with an air sac known as a swim bladder sometimes during deep sea fishing they spit it out when pulled up Fishes have a lateral line system Most species are oviparous but some have internal fertilization and birthing Subclass Sarcopterygii lobe fin Fleshy fins Three lineages survive and include coelancanths lungfishes and tetrapods Coelacanths were thought to have become extinct 75 mya but a living coelacanth was caught of the coast of South Africa in 1938 Important because it is believed they went on to become amphibians evolved into limbs and feet Lungfish African make a cocoon out of mud and breathe air during drought GROUPING TETRAPODA 4 feet FISH TO AMPHIBIANS BEST FOSSIL RECORD Specific adaptations 1 Four limbs feet with digits 2 A neck which allows separate movement of the head 3 Fusion of the pelvic girdle to the backbone 4 The absences of gills except some aquatic