topic16[1] - Topic 16 Deuterostomes Phylum Chordata(Ch 34 I...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Topic 16: Deuterostomes: Phylum Chordata (Ch. 34) I. Phylum Chordata (chordates) [clade] – general features A. key traits: deuterostomes with notochord, jointed appendages, and segmentation B. four key features present at some point in life cycle of all chordates: 1. dorsal, hollow nerve cord – becomes brain and/or spinal cord 2. notochord - flexible, fibrous rod along back (replaced by vertebrae in advanced vertebrates) 3. pharyngeal gill slits - openings in the throat region 4. postanal tail – most other animals with tails near the anus have anus at end of tail 5. these features may each be lost or altered in the adult 6. three subphyla: Cephalochordata, Urochordata, and Vertebrata II. Nonvertebrate chordates A. Subphylum Cephalochordata (clade) – lancelets 1. fishlike creatures that bury selves in mud and filter feed 2. all four key chordate feature present in adults 3. like vertebrates, muscles broken up into bands called myomeres (body segmentation) 4. essentially no brain in adults 5. Pikia - important shark B. Subphylum Urochordata (clade) – sea squirts, tunicates 1. barrel-shaped, sessile, filter-feeders 2. many secrete and live in a tough cellulose sac ( tunic ) as adults 3. only have pharyngeal gill slits as adults, other chordate characters only present in tadpole-like larvae 4. incurrent and excurrent siphons 5. no brain in adults III. Subphylum Vertebrata (clade) A. more properly called Craniata (read on and see if you can figure out why) B. characteristics 1. head with brain and skull 2. vertebral column – during development in most (all but Myxini), surrounding and ultimate replacement of notochord by bony or bone-like, hollow vertebrae; also, encase brain in protective box (skull or cranium ) of bone or cartilage 3. neural crest ectoderm – a unique set of stem cells that form near neural tube and migrate during development, involved in forming a variety of structures 4. highly developed internal organs unique kidney and excretory system endocrine glands (make many hormones) specialized heart; closed circulatory system 5. endoskeleton made of cartilage and/or bone cartilage and bone are tissues with compacted collagen protein fibers collagen matrix laid down first (provides flexibility) for bone, calcium phosphate is then deposited (provides rigidity) better than chitin – strong but not brittle (if you get enough calcium) C. excellent fossil record - bone makes great fossils; back to over 470 MYA D. living craniates in eight main classes 1. four considered fishes (Myxini, Cephalaspidomorphi, Chondrichthyes, and Osteichthyes) 2. four considered tetrapods (arose from fish; Amphibia, Reptilia, Aves, and Mammalia) 3. follow the evolutionary history as the major groups are covered IV. fishes – paraphyletic assemblage (grade) A. aquatic vertebrates that lack pentadactyl (5-fingered) limbs B. over half of all vertebrates; evolutionarily, the first vertebrates C. characteristics
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
1. gills – water comes through mouth and goes out throat slits covered with small blood vessels
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 6

topic16[1] - Topic 16 Deuterostomes Phylum Chordata(Ch 34 I...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online