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BIOL 211 - Pre-Midterm Notes

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BIOL 211
Vivian Dayeh

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BIOL  211  –  Introduction  to  Vertebrate  Zoology     Lecture  1:  Introduction     What  is  Vertebrate  Zoology?   − Study  of  animals  that  are  vertebrates   à  have  a  backbone  and  notochord     Why  Take  A  Course  in  Vertebrate  Zoology?   − Vertebrates  are  one  of  the  most  important  an d  abundant  groups  of  animals  on  earth.   − We  are  vertebrates,  so  when  we  learn  about  vertebrates  we  learn  about  ourselves  and  about   the  animal  “models”  most  useful  in  medical  research.   − Vertebrates  include  most  of  the  animals  we  use  in  agriculture  or  wish  to  m anage  as  natural   resources.   − We  know  more  about  the  evolution  of  vertebrates  than  any  other  gr    of  animals.   Vertebrates   − Very  diverse  à  more  than  63  000  extant  (living)  species  of  vertebrates   − Have  complex  and  diverse  body  forms  and  habitats   o Life  is  energetically  expensive  à  metabolically  active,  need  energy  from  food  to   carry  out  biochemical  processes   o Carnivores  à  eat  the  flesh  of  other  animals   o Herbivores  à  eat  plants;  have  to  feed  often,  since  plants  tend  to  have  a  lower   nutritional  value  than  other  types  of  food  sources   o Omnivores  à  eat  both  plants  and  animals     Groups  of  Vertebrates  (Figure  1.1)   − Two  major  groups  of  vertebrates   à  amniotes  and  non-­‐amniotes   − Non-­‐amniotes  à  embryos  enclosed  by  membranes  produced  by  the  female  reproductive   tract   o Able  to  live  an  aquatic  life  (in  water)   − Amniotes  à  embryotic  development  results  in  the  formation  of  an  extra  layer  ( amnion)   that  surrounds  the  embryo   o Adapted  to  survive  and  reproduce  on  land   o Don’t  have  to  worry  about  dehydration     Non-­‐Amniotes  (Figure  1.1)   1. Hagfishes  and  Lamprey   o Primitive  body  organization  (limbless,  boneless,  lack  jaws)   o Elongated  body   o Notochord  and  brain  are  present   o Feed  off  of  dead  organisms  (scavengers)   o Feeding  mechanism  involves  teeth -­‐like  structures  that  clamp  onto  prey,  tear  bits  off,   repeat   2. Chondritchthyes   o Ex.  sharks,  rays,  skates  (Elasmobranchs),  ratfishes  (Holocephalii)   o Contain  cartilaginous  skeletons  instead  of  bones   3. Osteichthyes  (boney  fishes)   o Very  diverse   o Ray-­‐finned  fishes  have  a  ray  structure  with  bones,  fleshy  bit  in  between  them  (ex.  perch,   trout,  bass)   o Lobe-­‐finned  fishes  have  flesh-­‐like  appendages  (ex.  coelacanth)   4. Amphibians   o Urodela  (salamanders)   o Anura  (frogs  and  toads)   o Gymnophonia  (caecilians)  have  no  appendages;  snake -­‐like     Amniotes  (Figure  1.1)     Sauropsids   − Extinct  sauropsids  include  dinosau rs  and  pterosaurs  (land),  ichthyosaurs  and  plesiosaurs   (ocean)   o Fossil  records  indicated  that  they  are  amniotes  in  terms  of  reproductive  capabilities   − Testudinia  (turtles)   − Lepidosauria  (tuatara,  lizards,  snakes)   o Scale-­‐covered  skin   o Tuatara  look  like  classical  reptile;  only  two  species  found  in  New  Zealand   − Crocodilia  (alligators,  crocodiles)   o Semi-­‐aquatic  predators   − Aves  (birds)   o ~10  000  species,  very  diverse   o Lineage  of  dinosaurs  that  evolved  flight;  there  are  some  flightless  birds,  however   o Feathers  and  feathered  wings  power  flight     Synapsids   − Monotremes  /  prototheria   o “Before  the  wild  beasts”   o First  wild  animals   o Egg-­‐laying  mammals   o Young  hatch  and  are  fed  with  milk  from  mother   o Ex.  echidna,  platypus   − Marsupials  /  metatherians     o “Behind  the  beast”   o Bear  fairly  undeveloped   young  that  make  their  way  into  a  pouch -­‐like  structure   where  they  feed  and  grow   o Developmental  process  occurs  within  the  pouch   o Ex.  kangaroo   − Placentals  /  eutherians   o “True  beast”   o Developmental  stage  occurs  within  the  womb/uterus  of  mother   o Gestational  stage  includes  the  development  of  placenta  where  nutrition  is  passed   from  mother  to  young   o Ex.  elephant     Vertebrate  Classification   − Classification  maximizes  information  content  and  unity   − Most  organisms  are  classified  into  groups  that  reflect  evolutionary  aspects   − Hierarchal  classification  à  different  levels  within  classification   − Binomial  nomenclature   o Species  à  set  of  organisms  which  are  similar  and  can  reproduce  sexually  among   themselves  but  are  reproductively  isolated  from  other  species   o Genus  à  similar  species  grouped  together     Phylogenetic  Systematics  (Cladistics)  à  used  to  determine  evolutionary  relationships  through   common  ancestors     Homology  (Ancestry)   − Homologous  structures  à  derived  from  the  same  structure  in  a  common  ancestor   − Homoplasy  à  similar  appearance;  may  not  necessarily  reflect  common  ancestry/function   − Analogous  structures  à  similar  functions;  may  or  may  not  be  an  overlap  in  homoplasy  or   homology     Parallel  Evolution  à  similarity  in  animals  with  similar  but  distant  ancestors   − Due  to  adaptation  to  similar  envi ronmental  conditions   − Ex.  long  legs  on  North  American  kangaroo  rats  and  African  jerboa     Convergent  Evolution  à  similarity  in  animals  with  very  different  ancestors   − Due  to  adaptation  to  similar  environmental  conditions   − Ex.  bat  and  bird  wings     Lecture  2:  Basic  Structure  of  Vertebrates     Vertebrate  Characteristics  (figure  2.4)   − Vertebrates  are  a  subphylum  of  the  animal  phylum   Chordata   − All  have  a  notochord  at  some  point  in  the  developmental  process  though  it  is  often  not  seen   once  maturity  is  reached  (it  becomes  a   different  structure)   o Notochord  à  a  turgid,  vascularized,  supportive  structure  surrounded  by  sheaths  of   connective  tissues   − Cephalization  à  hollow  dorsal  nerve  cord  above  the  notochord  with  anterior  brain   adjacent  to  the  three  spatial  sense  organs   − Cranium  à  specialized  structure  that  surrounds  and  protects  the  brain   − Bilateral  symmetry  à  left  and  right  sides  are  approximate  mirror  images   o Asymmetry  within  the  body   − Anterior  mouth  leads  to  a  digestive  tube  which  has  a  second  opening  (complete  gut)  so  that   flow  is  one  way   − Post-­‐anal  tail  extending  beyond  the  gut  region   − Gill  slits  in  anterior  part  of  gut  or  pharynx   − Coelomate  à  internal  space  (coelom)  houses  the  internal  organs   − Body  is  arranged  in  metameric  segments   o Composed  of  serially  repeated  units   o Most  evident  in  embryos   o Obscured  in  development,  especially  in  tetrapods   − Large  size  in  comparison  to  non -­‐chordate  species     Chordate  Relationships   − Closely  related  to  Echinodermata  (starfish,  sea  urchins)  based  on  developmental  and   molecular  data   − Three  subphyla:   1. Cephalachordata  (amphioxus)   2. Urochordata  (tunicates)   3. Vertebrata   − All  three  groups  together   à  Chordata   − Vertebrates  +  Urochordata   à  Olfactores     Animals  can  be  characterized  as  deuterostomes  or  protostomes  based  on  early  embryonic   development.   − Protostomes  include  mollusks,  arthropods,  annelids   o Coelom  originates  from  the  split  of  the  mesoderm   o Spiral,  determinate  cleavage   o Mouth  develops  from   blastopore   − Deuterostomes  include  chordates,  echinoderms,  hemichordates  (acorn  worms)  and   xenoturbellids  (small,  worm -­‐like  species)   o Radial,  indeterminate  cleavage   o Coelom  originates  from  outpouching  of  the  gut   o Blastopore  is  at  the  posteror  and  becomes  the  anus     Subphylum  Cephalochordata  (figure  2.2  c)   − ~27  species  of  small,  fish -­‐like  marine  animals  (ex.  lancelet)   − Amphioxus  is  a  chordate  with  both  vertebrate  and  non-­‐vertebrate  species   − Vertebrate-­‐like  features:   o Notochord  under  hollow  dorsal  nerve  chord   o Complete  gut  and  midgut  cecum   o Post-­‐anal  tail   o Perforated  pharynx   o Endostyle  à  in  pharyngeal  region,  helps  with  filter  feeding;  in  some  chordates,   it   becomes  the  thyroid  gland  and  produces  hormomes   o Segmentation  (myomeres)   − Non-­‐vertebrate-­‐like  features:   o No  cranium  or  other  skeleton   o No  special  sense  organs  and  brain   o No  kidneys   o No  heart     Subphylum  Urochordata  (figure  2.2  b)   − Tunicates  or  sea-­‐squirts   − Sedentary,  sessile  marine  mammals   − Unidirectional  flow  with  inlet  and  outlet  of  atrium   − Filter  feeding  à  filters  out  materials  that  it  eats  when  passing  water  through   − Brief  larval  stage  contains  a  notochord,  dorsal  hollow  nerve  chord,  muscular  post -­‐anal  tail   that  allows  it  to  be  free-­‐swimming   − Remnant  of  the  notochord  in  the  adult     Phylum  Hemichordata   − Acorn  worms   − Deuterostomes  that  used  to  be  considered  Chordata   − Stomatochord  is  not  homologous  with  the  notochord  of  chordates   − Perforated  pharynx     Phylum  Echinodermata   − Largest  phylum  of  deuterostomes  (other  than  chordates)   − Radial  cleavage   − Starfish,  sand  dollar,  sea  urchin,  sea  cucumber     Basic  Vertebrate  Structure   − “Vertebrate”  comes  from  the  serially  arranged  vertebrate  that  make  up  the  spinal  column   (backbone)   − In  land  vertebrates,  the  vertebrae  form  around  the  notochord  and  encircle  the  nerve  chord   o You  don’t  tend  to  see  this  after  a  certain  period  of  embryological  development   o Land  vertebrates  need  a  fairly  dense  region  to  withstand  high  pressure;  notochord   itself  isn’t  present   − Duplication  of  Hox  genes  indicate  embryological  development   − Neural  crest  à  involved  in  development  of  the  spatial  senses  and  the  brain     Early  Development     Egg  (Oocyte)  +  Sperm  (Spermatocyte)  à  Zygote  à  Embryo  à  Adult  organism     − Larva  à  a  free-­‐living  embryo  that  is  able  to  secure  its  own  nourishment   − An  embryo  has  three  germ  (tissue)  layers   o Ectoderm  à  forms  superficial  skin  layers,  line  the  most  anterior  and  most   posterior  digestive  tract,  nervous  system   o Endoderm  à  rest  of  digestive  tract  lining  and  lini ng  of  gut-­‐associated  glands  that   help  with  digestion;  respiratory  surfaces,  taste  buds,  thyroid,  thymus,  parathyroid   o Mesoderm  à  forms  everything  else  (muscles,  skeleton,  connective  tissue,   circulatory,  urogenital  system)   − Lateral  folds  à  made  up  of  layers  o n  top  of  each  other;  where  the  future  digestive  tract  is   seen  (figure  2.5)   o Further  folding  forms  the  head  and  tail  regions   o Within  that,  the  primitive  gut,  neural  tube,  notochord  form     Adult  Tissue  Types   − Form  from  lateral  folding   − Epithelia  à  protective  layer;  allows  for  nutrient/gas  exchange  (skin)   − Connective  à  supportive  structures   − Vascular  à  blood  vessels   − Muscular  à  movement  of  body/materials   − Nervous  à  signaling  information;  controls  and  coordinates  bodily  functions   − Organs  often  contain  most  of  the  five  ba sic  tissue  types     Connective  Tissue   − Collagen  à  a  fibrous  protein  that  is  found  in  areas  derived  from  the  mesoderm   o Important  tensile  strength   o Stiff,  doesn’t  stretch  easily,  forms  cable -­‐like  structures   o Sometimes  combine  with  elastin,  which  can  stretch  and  re coil     The  Integument   − External  covering  of  vertebrates   − Includes  skin  and  its  derivatives:  glands,  scales,  dermal  armour,  hair,  fur   − Skin  protects  the  body  and  receives  information  from  the  outside   o Specialized  receptor  cells  send  aspects  like  pain,  temperatur e;  others  can  detect   other  organisms,  electrical  impulses   − Made  up  of  two  layers:   o Epidermis  à  outermost  layer,  shed  continuously   o Dermis  à  underlies  the  epidermis     Mineralized  Tissues   − Hydroxyapatite  à  a  complex  compound  of  calcium  and  phosphorous  that  allows  tissues  to   become  very  strong   − Mineralized  tissues  are  composed  of  collagen  fibers,  cells  that  secrete  proteinaceous  tissue   matrix,  and  hydroxyapatite  crystals   − Extracellular  matrix  embedded  with  hydroxyapatite  crystals,  gives  rise  to  mineralized   tissues   − Include  mineralized  cartilage,  bone,  enamel,  dentine,  enameloid,  cementum   − Bone  à  a  dynamic  organ  that  can  be  remodeled  by  osteoblasts  and  osteoclasts   o Osteoclasts  à  bone-­‐breaking  cells   o Osteoblasts  à  bone-­‐forming  cells   o Osteoblytes  à  bone  cells   − Two  main  types  (figure  2.9c)   o Dermal  bone  à  formed  in  the  skin  with  cartilaginous  precursor   o Endochondral  bone  à  bone  develops  from  cartilage     Skeletomuscular  System  (figure  2.7)   − Notochord  à  stiffening  rod  running  the  length  of  the  body   − Gill  skeleton  à  keeps  the  gill  slits  open   − Next  came  the  dermal  skeleton  (external  plates)  and  the  axial  skeleton  (vertebrae,  ribs,  fin   supports)   o Some  primitive  fish  had  an  armor  outside  for  protection   − Then  came  the  appendicular  skeleton   o Made  up  of  the  cranial  skeleton  and  muscles,  and  the  axi al  skeleton  and  muscles   − Locomotion  is  due  to  serial  contraction  of  segmental  muscle  bands  in  the  trunk  and  tail   o Without  the  notochord,  there  would  be  no  lateral  bending  or  movement     Respiration  and  Ventilation   − Ancestral  (primitive)  chordates  relied  on  the   diffusion2  o2  gases  (O ,  CO )  across  a  thin  skin   o Smaller  organisms;  didn’t  need  specialized  structures   o Seen  in  amphioxus   − Cutaneous  respiration  à  gases  are  able  to  transport  through  the  skin,  which  must  stay   moist  for  this  to  occur   o Ex.  amphibians   − Due  to  their  large  size,  many  vertebrates  have  specialized  gas -­‐exchange  structures   o Ex.  diffusion  of  gases  into  and  out  of  the  blood  using  gills  for  water  and  lungs  for  air     Cardiovascular  System   − Blood  à  an  important  fluid  tissue  that  carries  a  variety  of  substances  t hroughout  the  body   − Blood  is  a  watery  matrix  with  cellular  components  that  is  made  up  of:   o Liquid  plasma   o Erythrocytes  à  red  blood  cells   o Leukocytes  à  white  blood  cells   o Thrombocytes  à  blood  clotting  cells  that  prevent  blood  from  escaping  a  damaged   region;  fragmented  in  mammals   − Nutrients,  water,  gases  carried  from  the  external  environment  to  tissues   o Without  2 ,  cells  can’t  respire  aerobically   − Wastes,  nutrients,  hormones  (signaling  molecules)  carried  between  tissues      the  body − Metabolic  wastes,  gases  (especially2  CO )  carried  from  tissue  to  the  external  environment   − Complexity  of  the  system  varies  from  organism  to  organism   o Closed  circulatory  system  à  arteries  are  connected  to  veins  via  capillaries;  in   order  to  pick 2up  CO ,  it  must  pass  through  the  respiratory  center  (ex.  gills)     Excretory  System  (figure  2.13)   − Kidneys  à  responsible  for  disposal  of  waste  products  (primarily  nitrogenous  waste)  and   regulation  of  water  and  minerals   o Na,  Ca,  Cl,  Mg,  K,  PO ,  HCO  are  regulated  by  this  system   4 3 o Tetrapods  use  kidneys   o Fishes  and  amphibians  use  gills,  skin,  kidney   − Kidneys  are  segmental  structures  that  are  made  up  of  three  parts:   o Protonephros  à  most  primitive   o Mesonephros   o Metanephros   − In  adult  fish  and  amphibians,  the  kidney  has  mesonephric  and  metanephric  portions   à   opisthonephric  kidney   − In  adult  amniotes,  the  bean-­‐shaped  kidney  only  has  the  metanephros     Reproductive  System   − Unsegmented  gonads   o Ovaries  (female)   o Testes  (male)   − Vertebrates  usually  have  two  sexes  since  sexual  reproduction  is  the  norm   − Gonads  are  paired  in  jawed  vertebrates  and  unpaired  in  jawless  vertebrates   o Usually  lie  in  the  posterior  body  wall  behind  the  peritoneum   o In  mammals,  the  testes  are  found  outside  the  body  since  the  body  temperature  is   too  high  for  normal  sperm  production     Nervous  System   − Works  with  endorine  syste m   − Receives  signals  from  inside  and  outside  of  the  animal  and  coordinates  a  response   − Neurons  à  the  basic  unit  of  the  nervous  system   − In  jawed  vertebrates,  the  axons  are  encased  in  a   myelin  sheath  which  facilitates  the  speed  of   nerve  impulse  conduction   − Nerves  running  between  the  CNS  and  the  body  are  called  the   peripheral  nervous  system   − Central  nervous  system  (CNS)  à  made  up  of  the  brain  and  spinal  cord   o Spinal  cord  receives  sensory  ( afferent)  information,  integrates  it  with  other  parts  of   the  CNS  and  sends  impulses  (motor/efferent  pathway)   o Considerable  autonomy;  doesn’t  require  higher  order  processing/thinking  within   the  brain  itself  (ex.  swimming  in  fish)     Endocrine  System   − Transfers  information  around  the  body  via  chemical  messengers  ( hormones)  in  the   bloodstream   − Hormones  initiate  a  response  in  target  cells  that  have  a  specific  receptor,  act  as  signaling   molecules     Immune  System   − Two  types  of  immune  response:   − Innate  immunity  à  the  organism  doesn’t  have  to  recognize  the  pathogen,  just  sees  that  it’s   a  foreign  entity  that  it  needs  to  get  rid  of   o All  animals  have  this   − Adaptive  immunity  à  immune  system  cells  recognize  specific  antigens   o Only  vertebrates  have  this   o Also  called  acquired/specific  immunity   − There  are  differences  in  immunity  between  jawless  and  jawed  vertebrat es   o Lampreys  and  hagfishes  have  leucine -­‐rich  repeat  molecules  and  lack  a  thymus   gland,  which  is  where  lymphocytes  are  developed   o Gnathostomes  are  jawed  vertebrates  that  have  specialized  lymphocyte  receptors     Lecture  3:  Early  Vertebrates   − An  important  feature  of  early  vertebrates  was  the  development  of  a  distinct  head  end  that   contained  a  tripartite  brain  within  the  cranium   o Tripartite  brain  à  forebrain,  midbrain,  hindbrain   − Active  predators  instead  of  sessile  filter  feeders   − Ostracoderms  are  extinct  jawless  fishes  whose  dermal  bone  formed  body  armor   − Early  soft-­‐bodied  vertebrates  were  small,  fish -­‐shaped  specimens  or  eel-­‐like  in  formation   − Chordates  since  they  contain  evidence  of  a  notochord  and  myomeres     Class  Agnatha   − Jawless  vertebrates   − First  lived  in  the  Cambrian   Era  (~500  mybp)   − Early  Agnathans  are  called  Ostracoderms  (“shell  skins”)  in  reference  to  their  bony  armor   − Some  extant  members  are  present  today     Ostracoderm  Characteristics  (figure  3.7)   − No  jaws;  still  have  a  mouth  region   − Single  nostril  on  top  of  the  head  ra ther  than  a  pair   − Tubular  gill  openings  as  opposed  to  slits   − Notochord  in  adults   − Pharyngeal  filter  feeding   − Endostyle  organ   − Few  or  no  paired  fins     Modern  (Living)  Agnatha   − Jawless  vertebrates  with  round  mouths   − Lack  specialized  reproductive  tracts  and  mineraliz ed  tissues     Hagfish  (Myxiniformes)  (figure  3.5  b)   − Marine  fish  that  feed  on  dead  fish  or  marine  mammals  (scavengers)   − Covered  in  mucus  glands  that  secrete  mucus  and  entrap  slime  on  the  hagfishes  body  when   threatened;  serves  as  a  deterrent  to  predator   − Mouth  has  two  horny  plates  that  have  tooth-­‐like  structures  made  of  dense,  keratin  protein   − Accessory  hearts  in  the  liver  and  tail  regions  in  addition  to  the  true  heart   − Females  outnumber  males   − Some  hermaphroditic  species   − Barbels  à  tentacle-­‐like  structures  that  surround  the  mouth  and  are  used  in  sensory  aspects     Lamprey  (figure  3.6  a,  c)   − Either  freshwater  or  anadromous  à  live  in  the  marine  environment,  spawn  in  fresh  water   − Nasohypophyseal  duct  à  single  nasal  opening  on  the  head  combined  with  duct  leading  to   the  pituitary  gland   − Larval  stages  live  in  streams  buried  in  the  sediment  and  filter  feed  during  development   o Time  spent  doing  this  depends  on  species,  but  is  typically  3 -­‐7  years   − Adult  lamprey  attach  onto  their  host  via  a  suction ed  round  mouth  found  in  the  oral  hood   o Use  tooth-­‐like  structures  to  cut  away  at  skin  and  protective  tissues  to  allow  for   feeding   o Feed  on  blood  and  fluid  from  host   o Often  parasitic,  detrimental  to  host   − Simple  digestive  system   − 7  pairs  of  gill  openings     Gnathostomes  (figure  3.8)   − Jawed  vertebrates   o Allow  for  new  feeding  behaviours  and  other  manipulations  (such  as  carrying   pebbles  to  build  a  nest  for  spawning)   o Origin  of  jaws  may  have  been  more  for  gill  ventilation  than  predation   − Extinct  gnathostomes  have  teeth  on  their  jaws   o Bony  fishes  and  tetrapods  ha ve  teeth  embedded  in  their  jaw   o Cartilaginous  fishes  have  teeth  formed  with  skin   − Evolution  of  teeth  must  have  happened  after  jaws  were  formed  (figure  3.9)   o Placoderms  are  an  extinct  group  of  gnathostomes  that  possess  jaws  but  not  teeth   within  jaws   − Four  distinctive  clades:   o Placoderms  à  highly  specialized,  extinct  armored  fishes   o Acanthodians  à  extinct  spiny  sharks   o Chondrichthyans  à  cartilaginous  fish   o Osteichthyans  à  bony  fishes     Placoderms  (figure  3-­‐9)   − Abundant  during  the  Devonian  period  (~400  mybp)   − Covered  with  bony  shield  on  anterior  portion  of  the  body   − Distinct  head  and  tail  regions   − Mineralized  endoskeleton   − Primarily  marine  but  some  lived  in  freshwater  or  estuarine  habitats   − Active  predator   − Jawed  with  tooth  plates  instead  of  teeth     Acanthodians  (figure  3.9)   − Spines  on  anterior  portion   − Extinct  species   − Multiple  paired  spines/additional  fins  along  with  the  pelvic  and  pectoral  fins   − Some  species  were  toothless;  others  had  tooth  whorls   o Tooth  whorl  à  rows  of  teeth  coming  one  after  the  next  that  are  continually  shed   and  replaced     Lecture  4:  Living  in  Water   − Much  of  the  earth  is  covered  by  water  (freshwater,  salt  water,  estuaries)   − Living  in  water  poses  some  challenges:   o Adjusting  buoyancy  to  stay  in  certain  areas  of  the  water  column   o Maintaining  body  temperature   o Maintaining  a  stable  internal  environment  due  to  the  movement  of  water,  ions,   waste   o Limited  gas  exchange  (especially2  O )     Obtaining  Oxygen  (figure  3.4  a)   − Many  aquatic  vertebrates  obtain  oxygen  from  the  water  and  remove  carbon  dioxide  from  the   body  via  gills   − Gills  of  teleosts  are  found  in  opercular  cavities  and  pharyngeal  pockets   o Water  passes  through  the  mouth,  is  pumped  across  gills  in  the  ercular  cavity o Operculum  à  covers  the  gills;  hinged  action,  prevents  backflow   − Gills  are  delicate  structures  that  project  off  of  t he  gill  arch  in  two  columns  of   gill  filaments   o Secondary  lamellae  à  finger-­‐like  projections  that  come  off  of  the  gill  filament  and   are  where  gas  exchange  occurs     Ventilation  Mechanisms   − Fish  pass  water  across  their  gills  so  gas  exchange  can  occur   − Buccal  pumping  à  mouth  and  opercular  cavities  pump  water  across  the  gills  due  to  the   production  of  positive  pressure   − Ram  ventilation  à  fish  swims  with  mouth  open  to  pass  water  across  gills   o Done  by  filter  feeding  and   pelagic  (bottom  dwelling)  fish   − Some  switch  when  actively  swimming;  some  just  rely  on  buccal  pumping  or  ram  ventilation     Gas  Exchange  (figure  4.2)   − Occurs  in  the  secondary  lamellae  of  the  gill   − Countercurrent  exchange  à  water  passes  through  the  gills  in  an  opposite  direction  to  the   blood   o Passing  in  the  same  direction  doesn’t  allow  for  adequate  gas  exchange   − Most  fish  use  gills  to  extract  oxygen  from  the  water   − In  a  hypoxic  environment  the  oxygen  level  in  the  water  is  too  low  so  another  way  to  get  the   required  oxygen  is  needed   o Lungs  used  by  gars,  lungfish,  tetrap ods   o Gulping  air  at  the  surface  is  passed  across  accessory  respiratory  structures   (labyrinth)     Buoyancy   − Air  within  the  body  of  an  aquatic  vertebrate  changes  buoyancy  (ex.  lungs,  swim  bladders)   − Mechanism  depends  on  the  type  of  aquatic  vertebrate   − Bony  fish  have  well-­‐developed  swim  bladders  (figure  4.3)   o Neutrally  buoyant;  stay  where  they  need  to  in  water  column   − Cartilaginous  fish  do  not  have  swim  bladders   o Adjust  buoyancy  based  on  very  fatty  liver   − Deep  sea  fishes  use  lipids  in  a  gas  bladder  or  through  the  body   − Air-­‐breathing  divers  need  to  return  to  the  surface  and  do  not  stay  at  one  depth     Sensory  Systems   − The  lens  of  aquatic  vertebrates  plays  an  important  role  in  the  focus  of  light  onto  the  retina   o More  refraction   o In  comparison  to  the  cornea  of  terrestrial  vertebr ates   o Teleost  lenses  are  round;  terrestrial  vertebrates  have  elongated,  oval -­‐shaped  lenses   − Mechanoreceptors  à  sense  touch,  pressure,  sound,  motion   o Lateral  line  à  detects  movement  and  vibrations  in  the  water  (figure  4.4)     Electricity  and  Water   − Water  conducts  electricity   − Some  organisms  produce  electrical  discharge  to  deter  predators,  for  courtship,  or  for   territory  defense   − Some  have  electroreception   o Ampullae  of  Lorenzini  à  in  sharks,  respond  to  small  changes  in  the  electric  field   and  allow  them  to  navigate  and  find  prey     Ion  Regulation   − Most  marine  invertebrates  and  hagfishes  are   isosmolal  to  seawater   − Marine  teleosts  and  lamprey  are   hyposmolal   o Water  flows  outward  from  the  blood  to  the  sea   − Coelacanths  and  cartilaginous  fish  are   hyperosmolal   o Water  flows  inward  fro m  the  sea  to  the  blood     Regulating  Waste  (figure  4-­‐10)   − Waste  products  need  to  be  removed  from  the  body  before  they  ch  toxic  levels o Ex.  ammonia  due  to  the  breakdown  of  protein   − Water  balance  and  waste  excretion  relies  on  the  kidney   o Nephrons  à  produce  urine  through  the  removal  of  excess  water,  salts,  wastes   o Glomerulus  à  a  capsule  that  surrounds  blood  vessels  and  filters  out  metabolic   waste  (ions,  water)  as  blood  crosses  across,  filtering  it     Nitrogenous  Waste   − Ammonia  is  very  toxic  to  aquatic  species   − Ammonotely  à  excretion  of  ammonia   o No  concentration   o Bony  fishes  release  ammonia  via  the  gills,  skin,  and  urine   − Ureotely  à  excretion  of  urea   o Mammals  can  synthesize  urea  from  ammonia  in  the  urea  cycle   o Less  toxic  overall;  can  concentrate   − Uricotely  à  excretion  of  uric  acid   o Reptiles  and  birds  conserve  water  by  producing  uric  acid   o Most  concentrated  form:  whitish  tinge,  low  amount  of  fluid     Body  Temperature   − Temperature  regulation  is  important  for  life   − Poikilotherm  à  variable  body  temperature   o Ex.  fish,  amphibians,  reptiles   − Homeotherm  à  stable  body  temperature   o Ex.  birds,  mammals   − Ectotherm  à  gains  heat  largely  from  external  sources  (environment)   − Endotherm  à  gains  heat  by  metabolic  processes   − Regional  heterothermy  à  different  temperatures  in  different  body  parts  (figure  4.14)   o May  use  muscles  to  warm  blood  that  has  gone  through  the  gills  to  keep  critical  parts   of  the  body  warm  while  other  parts  are  kept  at  water  temperature   − Marine  mammals  need  to  rely  on  an  additional  layer  of  fat  called   blubber  for  insulation   o Keeps  the  body  warm  enough  to  undergo  metabolic  process   o Also  used  as  an  energy  reserve   − Semi-­‐aquatic  mammals  have  water-­‐repellant  coats   o Oily/lipid-­‐like  material  deposited  on  the  fur  repels  water  so  that  it  doesn’t  soak  in   and  cause  the  organism  to  get  cold   − Other  mammals  have  fur  which  creates  a  barrier  between  the  cold  external  and  warm   internal  environments     Lecture  5:  Chondrichthyes     Chondrichthyes  (figure  5.1)   − Extant  cartilaginous  fishes  include:   o Sharks   o Rays  and  skates   o Chimaerans  /  ratfishes   − Can  be  divided  into  two  groups:   o Neoselachi  à  multiple  gill  openings  on  each  side  of  the  head  (ex.  sharks,  skates,   rays)   o Holocephali  à  singe  gill  opening  covered  by  a  fleshy,  opercular -­‐like  structure  (ex.   ratfishes,  chimaerans)     Chondrichthyian  Characteristics   − Do  not  have  bone  in  their  en doskeleton   o Cartilaginous  skeleton  gives  rise  to  buoyancy   − Teeth  and  scales  contain  dentin,  enameloid  and  traces  of  bone   − Dermal  denticles  /  placoid  scales  à  provide  protection,  help  avoid  turbulence  as  fish   swim  through  water  for  more  efficient  swimming   − Collagenous  structure  under  skin  acts  as  support  and  attachment  for  muscle   − Axial  and  appendicular  skeleton  becomes  mineralized  on  a  superficial  layer   o Crystalline  calcium  à  forms  tesserate  or  prismatic  endoskeleton  calcification   o Different  from  the  mineral  found  in  bone   − Cartilage  allows  for  an  increase  in  buoyancy  due  to  multiple   layers  and  internal  struts   − Lipid-­‐filled  liver  containing  oily  lipids  and  hydrocarbons
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