Study guide for Prelim 1 PDF

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1. Chordates a. Relatives of the vertebrates i. Hemichordates ii. Invertebrate chordates 1. Cephalochordates a. Lancelets or amphioxus 2. Tunicates (urochordates) a. Sea squirts iii. vertebrates b. Chordate = “string” = notochord i. Synapomorphies 1. Notochord a. Most species replaced by backbone, remnants found in intervertebral disks 2. Neural tube 3. Post-anal tale 4. Endostyle or thyroid gland a. Glandular structure on floor of pharynx b. Secretes mucus used in filter feeding c. Produces iodine-binding proteins ii. Ambulacraria 1. Echinoderms and hemichordates (based on molecular data) 2. Hemichordates a. Acorn worms and pterobranchs b. Half chordate c. Some, not all characteristics d. Lack notochord and post anal tale, precursor to endostyle e. 105 derived species, all marine f. 3 part body i. proboscis, collar, trunk iii. cephalochordates 1. lancelets, amphioxus (sharp at both ends) a. chordate character present in larva and all persist into adulthood b. 32 species, all marine c. 3-5 cm long d. wriggle backward into sand, filter feed e. cilia draw water into pharynx, and move food along digestive tract f. no specialized respiratory structures, no heart 2. synapomorphies a. notochord extends from tip to tip b. ring of oral cirri iv. tunicates (urochordates) 1. about 2500 species 2. some solitary, some colonial 3. sea squirts a. free-swimming larvae, non-feeding tadpoles

i. have all chordate characters, then endostyle develops b. adults are sessile, feeding i. have only endostyle, lack other features 4. Dramatic Metamorphisis a. Larva attaches to rock or piling b. Endostyle develops fully (adults feed, need mucus) c. Tale resorbed, notochord resorbed, nerve chord reduced to ganglion 5. Synapomorphies a. Tadpole larva b. Tunic i. Protein and tunicin ii. Gene for making cellulose, acquired by horizontal gene transfer from bacteria c. Heartbeat reversal i. Blood pumped toward pharynx ii. Short pause, then pumped toward intestine 6. Cephalo vs. uro a. Cephalo: head, head string, full length notochord including head b. Uro: tail, tail string, notochord extends through tail of larva 2. Vertebrates a. Synapos i. Vertebrate ii. Skull iii. Tripartite brain 1. Forebrain (olfaction) 2. Midbrain (vision) 3. Hindbrain (hearing and balance) iv. Neural crest and neurogenic placodes 1. Embryonic tissue that gives rise to nerve cells and other tissues during development 2. 3 tissues that form neurons (neural tube, neural crest, neurogenic placodes) vs 1 tissue in invertebrate relatives (neural tubes) 3. nueral crest cells a. form near the closing neural tube, migrate to sites where they give rise to structures such as cranial nerves, contribute to sense organs, endocrine glands, teeth, and gill arch skeleton b. like these cells, neurogenic placodes are migratory cells that form sensory neurons and sense organs v. Cranial nerves 1. Serve organs of head and upper body vi. Complex sense organs concentrated in head vii. Muscular gut tube 1. No cilia like in invertebrate relatives, allows for more powerful filter feeding and respiration 2. Permit larger body sizes and more active lifestyles 3. Muscles move food along rest of GI tract and expand and compress pharynx

b. Diversity >1 million living species of animals, 5% are vertebrates i. 63000 species chordates, 60000 vertebrates ii. invert: 700 mya, vert: 550 mya iii. factors that affect discovery 1. diversity of group, population size, ease of observation and sampling, body size, behavior iv. phylogenetic systematics (cladistics) 1. encodes info about evolutionary relationships 2. development of testable hypothesis 3. names for groups include info about major events in evo a. jaws: gnathostomata b. move to land: tetrapoda c. amniotic egg: amniota 4. synapomorphy: shared derived characteristic 5. symplesiomorphy: shared ancestral character v. crown vs stem groups 1. not all derived characters arise at once 2. crown group a. have all derived characters, includes extant species and fossil species 3. stem group a. fossil species with some of the derived characters of extant species b. for examples: Archaeopteryx i. recent birds: asymmetrical feathers, loss of digits, sternum w keel , reduced tale with pygostyle ii. archaeopteryx: no fusion of digits, no keel on sternum, long tail vi. Hagfish and Lamprey 1. Hagfish a. Rely on notochord for support as adults, recent evidence that have minute vertebral elements 2. Lamprey a. Rely on notochord for support as adults, have minute vertebral elements

c. Development i. Importance 1. Many characters used in phylogenetic analyses are developmental characters a. Presence/absence of neural crest cells b. p/a of amniotic membrane c. type of fertilization ii. embryogenesis includes 1. fertilization, cleavage, gastrulation, neurulation, organogenesis, cytodifferentiation iii. Basic developmental principles 1. Modes of induction a. Cell-cell contact b. Paracrine secretion c. Extracelluar matrix 2. Restriction, expression, and determination

a. 3. Epigenetics

a. 4. Epithelial versus mesenchymal organization a. Eplithelium: tightly attached cells like bricks on a foundation

b. Mesenchyme: cells scatter in extracellular matrix iv. Fertilization 1. External a. Animals release gametes to environment where fertilization occurs, primitive for verts, typical for aquatics 2. Internal a. Fertilization occurs in repro tract of female i. All chondrichthyans, some body fish, some amphib, all amniotes 1. Chondrichs have pelvic claspers and may wrap themselves around female to mate v. Cleavage 1. Serious of rapid cell divisions that partition the zygote into many smaller cells (embryo does not increase in size) a. Stages i. Morula (Solid ball of cells) ii. Blastula (hollow ball of cells) iii. Cell number increases with time vi. Gastrulation 1. Major movements of cells within embryo to form primary germ layers (embryo now called gastrula) a. Ectoderm (blue), mesoderm (red/pink), endoderm (yellow)

b. c. ectoderm i. forms nervous system, epidermis of skin and derivatives, sense organs d. mesoderm i. chordamesoderm forms notochord, rest of mesoderm makes muscle, bone, connective tissues, some organs (heart, kidneys, gonads) e. endotherm i. epithelial linings of tracts, some organs and glands vii. Neurulation 1. Toward end of gastrulation, ectoderm overlying the notochord begins formation of nervous system

2. Formation of neural tube from ectoderm 3. Organogenesis (formation of organs from germ layers) viii. Mark I Human

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ix. How neural crest cells migrate 1. Delamination: leave epithelium 2. Migration, arrest, condensation, and epitheliazation 3. Organ systems a. Integumentary b. Skeletal c. Nervous d. Importance of organ systems i. Relate organs within systems to the germ layers from which they develop ii. Many components of organ systems are shared derived characters of certain vertebrate groups iii. Three organ systems chosen demonstrate changes necessary in the move from water to land e. Integumentary system i. Skin ii. Derivatives of skin 1. Glands 2. Appendages (scales, spines, etc.) 3. Teeth

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4. Superficial bone (dermal bone) 5. Form through interactions of skin layers; neural crest often involved Bone develops in two ways 1. Endochondral ossification a. Mesenchyme forms cartilage model that is subsequently replaced by bone 2. Intramembranous ossification a. Bone formed directly from mesenchyme without cartilage precursor b. Mesenchyme: loosely packed cells in a gelatinous matrix from which connective tissues form Bones differ in the depth at which they form 1. Endoskeleton a. Deeper b. Composed of cartilage that is eventually replaced by bone through endochondral ossification 2. Dermal (integumentary skeleton) a. Superficial b. Bones develop in or just beneath skin by intramembranous ossification 3. Sometimes dermal bones are associated with endochondral bones, so difficult to distinguish Functions of integumentary system 1. Protection 2. Sensation 3. Communication 4. Regulation of body temp Skin structure 1. Epidermis a. Outer layer; thin; wears away b. Derived from ectoderm c. Cells can synthesize keratin 2. Dermis a. Inner layer; much thicker; doesn’t wear away b. Derived from mesoderm and neural crest c. Connective tissue; blood vessels; nerves d. Unique to verts 3. Hypodermis a. Subcutaneous layer (“beneath the skin”) b. Loose connective tissue that anchors skin to underlying tissues, muscles, organs c. Contains 50% of body’s fat stores in birds and mammals d. Derived from mesoderm e. Unique to verts 4. Vert skin changes from water to land a. Change from thin epidermis with mostly living cells to relatively thick epidermis with dead cells full of keratin at surface b. Glands become increasingly complex

5. Fish skin a. Basic structure of skin similar in most groups; nature of scales differs b. Most cells of epidermis are living c. Abundant mucus-producing glands in epidermis leads to slimy surface (most unicellular) d. Tissues that contribute to scales i. Enamel, dentine, dermal bone e. Placoid scales i. Shared derived character of chondrich ii. Develop in dermis and poke through epidermis iii. Do not grow with the fish, instead add new scales f. Osteichthyan scales i. Do not pierce epidermis ii. Scales grow with the fish iii. Types 1. Ganoid a. Thick surface coat of enamel, little or no dentine, bone underneath 2. Cycloid and ctenoid a. Lack enamel, have less bone, flexible 6. Amphibian skin a. Larvae have skin similar to fish, but lack scales b. Keratin produced after metamorphosis, but stratum corneum thin c. Cutaneous respiration very important; dermis extensively vascularized d. Abundant glandes (mucus, granular (poison)) e. Synapo: moist permeable skin with poison glands 7. Squamate (lizard and snake) a. Extensive keratinization (prevents water loss) surface cells of epidermis dead b. Scales present, but different from fish (folds of surface epidermis) 8. Bird skin a. Surface cells dead b. Scales along legs and feet (epidermal origin) c. Beak made of keratin d. Synapo: feathers (largely keratin, function in insulation, flight, display, several types) 9. Mammal Skin a. Surface cells dead b. Dermis produced dermal bones that contribute to skull and pectoral girdle (rarely find dermal bones in skin) c. Derivatives of epidermis are synapos i. Hair, sebaceous (oil) glands, eccrine and apocrine glands, mammary glands ii. Eccrine 1. Thermoregulation, improve adhesion

2. Sebaceous a. Waterproof, lubricate 3. Apocrine a. Communication and defense iii. Other derivatives 1. Claws, nails, hooves, antler, scales vii. Teeth 1. Teeth of hagfish and lamprey are made of keratin (not true teeth) 2. Gnathostomes have true teeth a. Out enamel layer, inner dentine later, pulp cavity b. Some groups have secondarily lost teeth c. Development of enamel and dentine occurs as a reciprocal epithelial mesenchymal interaction

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3. Skeleton System functions i. Protection of internal organs ii. Movement (attachment site for muscles) iii. Storage site for fat and minerals iv. Production of formed elements of blood v. Bone growth 1. Most verts: indeterminate (continues throughout life) 2. Birds and mammals: determinate (Stops at adulthood) a. Growth occurs at epiphyseal plates (cartilaginous zone of growth) b. Epiphyseal plates eventually become ossified and growth stops

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vii. Bone remodeling 1. Even within verts with determinate growth, bone deposition and absorption continue after full height/length is reached a. Osteoblasts deposit bone b. Osteoclasts break down bone 2. Influenced by hormones and amount of stress put on bone a. Bone forms in response to stress b. Bone absorbed when not stressed c. Example: shrew very small and must eat often, in winter can reduce body size by 45%, decrease by resorption and changes regulated by hormones 3. Regions of skeleton a. Cranial (head) and postcranial (trunk and tail) viii. Bone develops in two ways 1. Endochondral ossification: mesenchyme forms cartilage model that is subsequently replaced by bone 2. Intramembraneous ossification: bone formed directly from mesenchyme without cartilage precursor ix. Cranial Skeleton 1. Chondrocranium: endoskeletal elements that protect brain, nose, inner ear 2. Splanchnocranium: endoskeletal arches that support pharynx, gills, and jaws 3. Dermatocranium: dermal elements that cover the chondrocranium and splanchnocranium 4. Neural crest plays major role in forming all 3 5. Chondrocranium a. Chondros=cartilage, kranion=skull b. Main function is protection c. Usually a trough of cartilage and cartilage-replacement bone i. Covers brain ventrally, caudally, and partly laterally ii. Encapsulates inner ear and nose 6. Splanchnocranium a. Splanchnon=gut b. Also called visceral skeleton, functions in respiration and feeding c. Series of arches of cartilage or cartilage-replacement bone that lie in wall of pharynx i. Better developed in fishes, where arches support gills

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8. Dermatocranium a. Derma=skin b. Superficial dermal bones that cover the chondo, splanchno, and muscles association with splancho/jaws c. Functions in protection and feeding x. Cranial Skeleton and Phylogeny 1. Jawless fishes: lampreys a. Small chondrocranium, splancho consists of cartilaginous visceral arches (superficial, not articulated); no jaws i. Arches 1 and 2 support oral hood and tongue ii. Arches 3-7 form branchial basket iii. No dermatocranium 2. Gnathostomes a. Chondrocranium b. Deep articulated gill arch skeleton medial to gills; jaws c. Dermatocranium i. Note: chondrich: NO dermatocranium 1. Osteichthyes and beyond YES xi. Changes in Splanchnocranium with move to land 1. Expect major changes with change from gill to lung breathing 2. Parts of splanchno a. Become modified to form supports for floor of mouth and newly evolved tongue b. Become incorporated into larynx and trachea c. Form middle ear ossicles i. Three mammaliam ear ossicles evolved from portions of the mandibular and hyoid arches of fishes xii. Postcranial skeleton 1. Axial a. Notochord, vertebral column, ribs, sternum 2. Appendicular a. Paired appendages and their supporting girdles (pectoral and pelvis) 3. Consists almost entirely of endochondral bone 4. Changes with move to land a. Fishes: pectoral girdle attached to skull (no neck) i. Pelvic girdle not attached to vertebral column b. Tetrapods i. Both girdles are more robust, and pectoral girdle loses attachment to skull (gains neck, greater mobility of head, reduced jarring) ii. Pelvic girdle attached to vertebral column xiii. Tetrapods vs. fish 1. More robust vertebral columns 2. Greater regional differentiation of vertebrae 3. Vertebrae with more processes 4. Nervous System a. Cellular compenents

i. Neurons- excitable cells that generate and transmit messages ii. Glial cells- supporting cells that outnumber neurons 10 to 1, (neuroglia) 1. Functions a. Provide structure support for neurons b. Nurture neurons (provide growth factors) c. Form myelin sheaths i. Layer that covers axons in pns and cns ii. Multiple wrappings of plasma membrane around glial cells iii. Aids in rapid conduction of impulses iv. Synapo of gnathostomes v. Multiple sclerosis: myelin sheaths destroyed b. Central nervous system i. Brain and spinal cord develop from a neural tube ii. Tripartite brain is a shared derived character of verts iii. Increase in brain size w/ increase in body size 1. Tremendous variation within groups of verts 2. Increase in size of forebrain c. PNS i. Cranial nerves synapo of verts ii. Nerves with roots enclosed within skull iii. Some sensory some motor iv. Formed from neural tube, neural crest, neurogenic placodes v. Fish: 10 pairs and 6 in lateral line, humans: 12 vi. Move to land 1. Lose lateral line nerves, except in some amphibians 2. Gain cranial nerves vii. Protection 1. Bony or cartilaginous cases, meninges (layers of connective tissue), cerebrospinal fluid 2. Meninges a. Derived from neural crest and mesoderm b. Fishes: single membrane c. Amphibs and reptile: two membrane d. Bird and mammals: 3 e. Dura mater (out): tough mother, arachnoid (middle): spider form, pia mater (in): tender mother 3. Cerebrospinal fluid a. Continuously produced by capillaries in the ventricles of the brain b. In mammals is found i. in space between arachnoid and pia mater ii. Within ventricles of brain iii. In central canal of spinal cord 5. Sensory systems a. Lateral line i. Detects water disturbance, lost with move to land b. Hearing and equilibrium

i. Detects pressure waves and changes in body position and movement, modified with move to land c. Electroreception i. Detects weak electric fields, lost with move to land, re-evolved at least once in amniotes d. Neural crest and neurogenic placodes i. Placode: any thickening of ectoderm caused by increasing height of cells or number of cells ii. Neurogenic: gives rise to neurons iii. Similarities 1. Derivatives of ectoderm 2. Migratory cells 3. Form sense organs and sensory neurons iv. Differences 1. All neurogenic placodes originate on the head; neural crest originates on either the head or trunk 2. Neural crest cells form motor neurons (placodes do not) 3. Placodes form sensory receptors (neurons do not) e. Sensory receptors i. Specialized cells that monitor the internal and external environment ii. Classified according to the stimulus to which they respond 1. Mechanoreceptors a. Responsive to small changes in mechanical force b. Lateral line; hearing and equilibrium 2. Electroreceptors a. Responsive to weak electric fields b. Electroreception iii. Lateral line system 1. Enables detection of water disturbance: movement of water moves cupula, which moves extensions of hair cells and changes firing 2. Ancient sensory system of vertebrates; considered shared derived character of verts 3. Present in hagfish, lamprey, cartiliganious fish, bony fish, larval amphibs 4. Lost in all amniotes 5. Serious of mechanoreceptive organs in the skin a. Organs are arranged as lines b. Some on skin surface, some in canals 6. neuromast organs contain hair cells whose extensions project into overlying gelatinous mass (cupula) 7. movement of water moves cupula, which moves extensions of hair cells and changes rate of firing 8. In hagfish a. Adults have skin grooves of unknown function; do not have neuromast organs typical of later line i. Embryonic hagfish have laterline placodes that give rise to neurmast primordial, which later transforms to skin grooves ii. Present, but degenerate in hagfish

iv. Sensory structures of hearing and equilibrium are located in the inner ear v. All verts have inner ear embedded in otic capsule of skull 1. Vestibular apparatus- equilibrium a. Semicircular canals and chambers b. Entire apparatus filled with fluid, and hair cells located at base of canals embedded in gelatinous mass (cupula) which are in chambers c. Hagfish: 1, lamprey: 2, gnath: 3 d. Maintain equilibrium i. Hair cells in semicircular canals important when head or body is moving ii. Hair cells in utriculus and sacculus important in detecting position of head with respect to gravity (static equilibrium) 1. Otoliths shift, movement detect by hair cells 2. Area devoted to hearing – cochlea in mammals 3. Some tetrapods have middle and external ear a. Hear by sound waves passing through air must set fluid in inner ear in motion, external ear collects and directs, middle ear amplifies vi. Hearing in fish 1. Inner ear with hair cells, lack middle and external regions, ears do not open to outside of body 2. Sound reaches and stimulates hair cells in ear by several routes (tissues) a. Through swim bladder (NOT FOR CHONDRICHS) vii. Electroreception 1. Evolved from lateral line system, in sharks,skates/rays: ampullae of lorenzini” 2. Structure a. Subcutaneous tube b. One end opens by pore to skin surface c. Entire tube filled with gelatinous material that conducts electricity d. Usually on head 3. Function a. Detect electric fields around prey (muscle contraction) 4. Not found in hagfish, found in lamprey and gnathostomes and fish a. Lost in frogs and amniotes i.e. except dolphins and platypus on beak 6. Life in Water a. Ventila...