Phylum Chordata 1

2 Porifera Platyhelminthes Mollusca Arthropoda Hemichordata Cnidaria Nemertea Annelida Echinodermata Chordata Lophophores Protozoans

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Chordates 5

Chordate Relatives Common ancestry revealed by dorsal nerve tube and pharyngeal gill slits Gill slits form (throat pocketings) at some time during development; used for feeding or gas exchange 6

Deuterostomes the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.

Phylum Hemichordata Three body regions –Proboscis –Collar –Trunk Deuterostome Gill slits Open circulatory system Dorsal and ventral nerve cord 8

Phylum Chordata Three subphyla unified by having a notochord at some point in life cycle and metameric tail Notochord = densely packed muscle fibrils enclosed by sheath in rod shape; provides skeletal support –From which spinal column develops Metameric tail = repetition of similar segments; extends beyond anus 9

Phylum Chordata 10

Phylum Chordata Notochord Gill slits or pharyngeal pouches Dorsal hollow nerve cord Postanal tail Segmented muscles Deuterostome 11

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Evolutionary Adaptations of Chordates From filter feeding ancestors to active predators –Mobility –Oxygen capture –Digestion –Circulation –Nervous system 16

Skeletal Changes Skeleton becomes stronger to work with bigger muscles Allows more rapid movement 17

Oxygen Capture Gill slit and muscular pharynx will move more water over gills –More oxygen is extracted from water 18

Circulation Stronger heart to circulate blood faster 19

Digestion Digest more food –Muscularized gut –Digestive glands Liver Pancreas 20

Nervous System More complex for better –Motor control of body to capture food –Sensory detection of the animals environment –Integration centers (brain) 21

Brain With Three Parts Forebrain Midbrain Hindbrain 22

Chordate Subphyla Phylum. ChordataPhylum. Chordata –Subphylum. Urochordata –Subphylum. Cephalochordata –Subphylum. Vertebrata Phylum. ChordataPhylum. Chordata –Subphylum. Urochordata –Subphylum. Cephalochordata –Subphylum. Vertebrata 23

Subphylum Urochordata 3000 species of tunicates or sea squirts Earliest derivative of chordate line Adults bear no resemblance to other chordates, but larval features indicate nerve cord and notochord These disappear during metamorphosis Only chordate feature remaining = gill slits (filter feed) 24

Subphylum Urochordata Sea squirts Gill slits (pharyngeal slits) Notochord –Only in larva Adult has tunic 25

Sea Squirts 26

Subphylum Urochordata Soft-bodied marine filter feeders Wide variety of sizes, shapes, and colonial structure All have outer covering (tunic) containing tunicin (cellulose-like) and in/ex-current siphons 27

Subphylum Cephalochordata Small group of 23 species of lancelets or amphioxus Fish-like and free swimming, also burrow in sand with only head protruding Unique feeding apparatus for suspension feeding (buccal cirri/gill slits) Resemble vertebrates more; may represent living descendants of vertebrates 28

Subphylum Cephalochordata Amphioxus Notochord length of body Dorsal hollow nerve cord Gill slits Segmented muscles 29

Amphioxus 30

Around 49,000 species of vertebrates Significant not in size or age of group, but its morphological diversity, structural complexity, and trophic dominance Three novelties bind all vertebrates Subphylum Vertebrata 31

Subphylum Vertebrata Neural crest tissue = specialized kind of ectoderm that gives rise to nervous system, retina, gill cartilage, and pigment cells Enlargement of anterior end of neural tube to form the brain Endoskeleton = backbone composed of vertebrae (bony/cartilaginous segments replace notochord during development), cranium (bony/cartilaginous housing for brain), paired pectoral and pelvic appendages 32

Subphylum Vertebrata All are bilaterally symmetrical with regional differentiation Head region = houses sensory organs, brain, anterior opening to digestive tract Trunk region = body cavities that house viscera (internal organs) Tail or caudal region = lacks viscera, but has muscles and skeleton (function in locomotion, reduced, or specialized) 33

Subphylum Vertebrata Metamerism (serial repetition of body parts) limited to trunk muscles, skeleton (vertebrae and ribs), and the nerves associated with trunk All have gills at some point in life cycle (breathing organs or transient developmental structures) Closed circulatory system = arteries move blood to periphery from multi-chambered heart, veins move blood from periphery to heart, capillaries Myomeres associated with endoskeleton 34

Vertebrate Classes 35

Vertebrate Diversity Major evolutionary innovations among vertebrate groups fall into four categories: 1. Musculoskeletal system 2. Nervous system 3. Respiratory/circulation systems 4. Nature of the egg 36

Musculoskeletal system Most primitive in jawless vertebrates (hagfish, lampreys), have reduced braincase and cartilaginous gill-arch supports Hagfish = only notochord Lamprey = notochord strengthened by addition of small arches of cartilage in anterior trunk segments and small blocks of cartilage posteriorly--These are evolutionary precursors to vertebrae! 37

Musculoskeletal system All other vertebrates: –replacement of notochord with bony* vertebrae--articulate, protective housing for nerve cord –development of pectoral/pelvic appendages (from fins to limbs) –appearance of jaws associated with braincase *cartilage in sharks/rays- descended from bony ancestors 38

Nervous System Increased structural complexity allowed an elaborate nervous system to evolve Cephalization: elaboration of the anterior end of spinal cord to form hollow brain and sensory organs (protected by skull) Peripheral nervous system: paired nerves in every body segment (relay brain’s messages to periphery) 39

Nervous System Autonomic nervous system: function automatically without voluntary control by brain –Sympathetic: increases activity, slow digestion –Parasympathetic: decreases activity, stimulate digestion –This complementary system best developed in mammals so they can maintain metabolic activity while still able to respond to external conditions 40

Respiratory/Circulation Respiration: –Vertebrates require more oxygen than inverts, birds/mammals = highest demands (endothermic) –Soft skin, moist environment (eel, amphibian) = gas exchange across skin in addition to respiratory organ –Gills or lungs = derived from the pharynx –Water pumped across gills, get gas exchange 41

Respiratory/Circulation –Air breathed into lung, gas exchange across epithelial lining –Birds also have air sacs extending from lungs into many parts of body –Mammals have diaphragm to forcefully pull air in/expel air out

Respiratory/Circulation Circulation: –Allied with respiratory system: transports oxygen, nutrients, and water to cells and removes wastes/carbon dioxide –All systems closed: heart, arteries, veins, capillaries 43

Respiratory/Circulation –In gilled, 2-chamber heart: one atrium, one ventricle, blood enters heart via veins, leaves via aortic arches in gills (gas exchange), blood proceeds to rest of body –In amphibians, aortic arches are reduced and modified into vessels in order to pass blood from lungs to 3-chambered heart (atrium separated by septum, one ventricle)

Respiratory/Circulation Circulation: –In snakes and lizards, ventricle also has septum (incomplete 4-chambers) –In birds and mammals, complete separation of oxygenated/deoxygenated blood, 4-chambered heart, efficient system with no mixing gives greater blood volume and higher blood pressure (needed for metabolic requirements) 45

Excretion –Kidneys = separate food/water from excess salt/waste in blood

The Egg Eggs enclosed by plasma membrane internally and vitelline membrane externally Fish and amphibian eggs pass down oviduct where chitinous chorion or gelatinous protein-polysaccharide material added (anamniote egg = no amniotic membrane) External fertilization; moist climate to prevent desiccation 47

The Egg Evolution of amniote egg: equipped with extra membrane layers of protection (amnion, yolk sac, chorion, allantois) as well as a leathery/calcareous shell In reptiles and mammals (monotremes); fertilization internal; subject to predation Marsupials and placental mammals retain young internally (helps young develop to an advanced stage before born) 48