Oat Reading Comprehension Practice Test 6p5f49

                       

                           OAT  Reading  Comprehension  Sample  Test                                                

   

  Embryogenesis       1) The   starting   point   for   the   production   of   a   new   individual   by   sexual   reproduction  is  the  fertilized  egg,  or  zygote.  Repeated  mitotic  divisions  result   in  many  cells  that  differentiate  to  form  the  tissues  and  organs  of  the  developing   individual  or  embryo.       2) Soon   after   an   egg   is   fertilized,   the   single-­‐celled   zygote   becomes   two   cells,   the   two   divide   into   four,   and   so   on.   This   process   of   cleavage   partitions   the   egg   substance  into  an  increasing  number  of  smaller  cells,  or  blastomeres,  each  with   an   equal   number   of   chromosomes.   The   cleavage   divisions   are   unusual   because   they   are   not   separated   by   periods   of   cellular   growth;   the   zygote   mass   is   the   same  at  the  end  of  cleavage  as  at  the  start.  The  size  distribution  of  the  cells  and   the  kind  of  division  are  a  function  of  the  amount  and  distribution  of  the  yolk.   Cleavage   is   termed   holoblastic   when   an   entire   egg   cell   divides,   as   in   the   frog,   and  meroblastic  when  only  part  of  the  cell  divides,  as  in  the  chick.     3) As  holoblastic  cleavage  occurs,  as  in  amphibians,  the  cells  become  arranged  in   the   form   of   a   hollow   ball,   or   blastula,   within   which   a   central   cavity,   the   blastocoels,   appears.   Two   major   regions   are   evident,   an   upper   animal   hemisphere,   or   pole   of   small   dark   cells   with   little   yolk,   and   an   opposite   vegetal   hemisphere  below,  of  larger,  pale-­‐colored  cells  rich  in  yolk  granules.  Between   them  is  a  marginal  zone  of  medium-­‐sized  cells.       4) As  cells  continue  to  proliferate,  an  inrolling  or  involution  begins  directly  below   the   center   of   the   gray   crescent,   a   lightly   pigmented   area   of   the   egg   cortex   important   in   guiding   early   stages   of   development.   A   slit   forms,   and   the   fold   above   it   is   the   dorsal   lip   of   the   blastopore,   derived   from   the   crescent.   The   cells   of   the   animal   hemisphere   move   inward   more   rapidly   than   the   larger,   fewer   yolky   cells   of   the   vegetal   hemisphere.   The   slit   extends   laterally   and   downward   and  eventually  forms  a  ring  of  involuting  tissue,  the  blastopore,  which  moves   over   the   yolk-­‐laden   vegetal   hemisphere   and   increasingly   encloses   it.   This   process  of  overgrowth  is  called  epiboly.       5) Once   inside   the   embryo,   the   involuting   cells   move   away   from   the   blastopore   and   form   the   walls   of   an   enlarging   chamber,   the   archenteron   (or   gastrocoel)   which   is   the   cavity   of   the   primitive   gut.   The   infolding   process   is   called   invagination.   As   the   archenteron   enlarges,   the   blastocoel   is   gradually   obliterated.   This   is   now   called   the   gastrula.   Epiboly   and   invagination   are   accomplished  without  change  in  the  overall  mass  of  the  embryo,  indicating  that   growth   plays   no   part   in   the   process   of   gastrulation.   When   complete,   the   gastrula   consists   of   an   outer   layer   of   ectoderm   from   cells   of   the   animal   hemisphere,   and   inner   layer   of   endoderm   called   entoderm   from   cells   of   the   vegetal   hemisphere,   and   between   these   a   third   layer,   mesoderm.   Since   the  

latter   at   this   stage   includes   the   presumptive   notochord,   it   may   be   called   chordamesoderm.       6) Most  of  the  mesoderm  invaginates  by  rolling  over  the  lateral  and  ventral  lips  of   the   blastopore.   However,   the   portion   giving   rise   to   the   notochord   moves   inward  over  the  dorsal  lip  and  is  preceded  by  the  prechordal  plate  mesoderm   of  the  head.  These  are  the  germ  layers  from  which  various  tissues  and  organs   will   form.   The   ectoderm   will   produce   the   external   covering   of   the   body,   the   nervous  system,  and  the  sense  organs;  the  endoderm  provides  the  lining  of  the   digestive   tract,   its   glands,   and   associated   structure;   and   the   mesoderm   gives   rise   to   the   ive   tissues,   muscles,   lining   of   the   body   cavity   and   other   parts.     7) At   the   end   of   gastrulation,   when   all   the   endoderm   is   inside,   the   original   egg   axis  has  rotated  about  90  degrees.  The  former  lower  end  of  the  axis  then  at  the   completed   blastopore,   marking   the   posterior   end   of   the   future   animal.   The   chordamesoderm   cells   indicate   the   dorsal   region;   and   shortly   after   gastrulation   the   paired   neural   folds   on   the   surface,   forward   from   the   blastopore,  provide  an  external  indication  of  the  dorsal  surface.     8) After  gastrulation,  major  differentiation  of  the  embryo  begins.  From  the  three   germ   layers   there   are   outpocketings,   inpocketings,   thickenings,   divisions   and   other  changes  that  lead  to  the  establishment  of  the  organs  and  organ  systems.   The   nervous   system   starts   dorsally   as   a   pair   of   neural   folds.   The   ectoderm   between  these  sinks  down  and  the  folds  come  together  to  form  a  neural  tube,   enlarged  at  the  anterior  end  to  become  the  brain.  On  either  side,  between  the   neural   tube   and   ectoderm,   a   line   of   cells   forms   the   neural   crests   that   will   produce   the   dorsal   or   sensory   roots   of   spinal   nerves   to   grow   into   the   cord.   Motor   roots   later   grow   out   ventrally   from   the   cord.   The   neural   crests   also   contribute   sympathetic   ganglia,   the   Schwann   cells   of   nerve   fibers,   pigment   cells,  and  important  cartilage  elements  of  the  brachial  complex.     9) The   early   brain   has   three   primary   vesicles,   the   forebrain,   midbrain   and   hindbrain.   The   forebrain   produces   the   cerebral   hemispheres   and   diencephalon,   and   from   the   hindbrain   the   cerebellum   and   medulla   oblongata   are   derived.   A   rounded   optic   vesicle   grows   laterally   on   either   side   of   the   forebrain   and   stimulates   the   ectoderm   on   the   side   of   the   head   region   to   form   a   thickened   lens   vesicle   that   subsequently   produces   the   lens   of   the   eye.   Meanwhile,   the   outer   surface   of   each   optic   vesicle   becomes   concave   by   invagination  and  forms  the  retina.     10) The   endoderm   of   the   primitive   gut   becomes   the   inner   lining   of   the   digestive   tract.   Anteriorly,   at   the   future   pharynx,   three   outpocketings   of   the   tract   on   either   side   meet   three   corresponding   inpocketings   from   the   side   of   the   neck;   these  break  through  to  form  the  gill  slits.  A  single  ventral  outpocket,  behind  the   pharynx,   forms   the   liver   bud   that   becomes   the   liver   and   bile   duct.   An  

inpocketing  of  ectoderm  called  stomodeum  forms  ventrally  on  the  head  region,   and   a   similar   one   called   proctodeum   at   the   posterior   end.   In   later   embryonic   life   these   break   through   to     the   endoderm   of   the   digestive   tract,   the   stomodeum   becoming   the   mouth   cavity   and   the   proctodeum   becoming   the   anal  canal,  both  lined  by  ectoderm.  During  larval  life  a  ventral  outpocket  of  the   pharynx  grows  posteriorly  and  divides  into  two  lobes.  The  anterior  part  gives   rise  to  the  larynx  and  trachea  and  the  lobes  to  the  lungs.     11) During  gastrulation,  the  mesoderm  grows  inward  and  penetrates  between  the   ectoderm  and  endoderm.  Cells  in  its  middorsal  part  become  arranged  as  a  solid   rod,   the   notochord,   between   the   nerve   tube   and   primitive   gut,   to   serve   as   a   ing   body   axis.   Prospective   mesoderm   at   either   side   of   the   notochord   grows  down  as  a  curved  plate  between  the  ectoderm  and  endoderm,  and  the   two  meet  ventrally  under  the  yolk-­‐laden  cells.  The  thin  lower  part  of  each  plate   called   hypomere   splits   into   two   layers.   The   outer   is   applied   to   the   ectoderm   and   becomes   the   parietal   peritoneum,   the   inner   surrounds   the   gut   to   make   the   visceral  peritoneum  and  smooth  muscle  of  the  gut,  and  the  space  between  the   layers  is  the  body  cavity,  or  coelom.  The  upper  most  mesoderm  called  epimere   at   either   side   of   the   nerve   tube   and   notochord   forms   a   lengthwise   series   of   segmental   blocks   or   somites.   Each   somite   differentiates   into   three   parts:   a   thin   outer  part  called  dermatome  becomes  the  dermis  of  the  skin,  a  thick  inner  part   called  myotome  gives  rise  to  voluntary  muscles,  and  nearest  the  notochord,  a   scattering  of  cells  called  sclerotome  grow  about  the  neural  tube  and  notochord   to   form   the   vertebrae   or   axial   skeleton.   Between   the   ventral   plates   and   the   somites   a   third   portion   called   mesomere   is   the   forerunner   of   the   excretory   system  and  parts  of  the  reproductive  system.                                        

Questions:     1. TRUE  about  embryogenesis:     A. The   process   of   cleavage   partitions   the   egg   substance   into   an   increasing   number  of  smaller  cells  with  smaller  number  of  chromosomes.   B. At   the   end   of   gastrulation,   when   all   the   endoderm   is   inside,   the   original   egg  has  rotated  about  90  degrees.   C. Epiboly   and   invagination   causes   a   change   in   the   overall   mass   of   the   embryo.   D. Amphibians,  like  frogs,  undergo  meroblastic  cleavage.   E. All  of  the  above     2. The  mesoderm  gives  rise  to  which  part/s  of  the  body?     A. Muscles   B. Cartilage  elements   C. Nervous  system   D. Mouth     E. None  of  the  above     3. Bert,   a   20   year-­‐old   male,   came   into   the   veterinarian’s   clinic   to   consult   something   regarding   his   dog   named   Troy.   According   to   Bert,   Troy   seemed   “not  to  hear”  anything  since  his  puppy  days.  Bert  also  reported  that  he  also   had   a   hard   time   calling   Troy   and   that   Troy   seldom   barks.   After   some   tests,   the   veterinarian   said   that   Troy   is   deaf   and   that   Troy   did   not   develop   his   sense  organ  for  hearing.  Defect  in  which  germ  layer  caused  Troy’s  deafness?     A. Endoderm   B. Mesoderm   C. Entoderm   D. Ectoderm     E. Chordamesoderm       4. Knowing  a  defect  in  this  germ  layer,  what  other  body  parts  of  Troy  could  also   have  been  affected?     A. Anal  canal   B. Myotomes   C. Visceral  peritoneum   D. Larynx   E. Nervous  system     5. Bert   also   asked   the   veterinarian   if   Troy’s   deafness   would   affect   his   reproductive   system.   According   to   Bert,   he   wants   to   have   puppies   from   Troy   that’s  why  he  is  concerned  about  this  matter.  The  veterinarian  told  Bert  that   Troy   can   still   have   puppies   because   the   reproductive   system   arises   from   a   different  germ  layer  called:     A. Endoderm   B. Mesoderm   C. Entoderm   D. Ectoderm   E. Chordamesoderm        

  6. Which  of  the  following  processes  causes  obliteration  of  the  blastocoel?     A. Cleavage   B. Epiboly   C. Invagination   D. Gastrulation   E. None  of  the  above     7. Which  of  the  following  statements  is/are  NOT  true  about  the  nervous  system   formation?     A. The  nervous  system  starts  dorsally  as  a  pair  of  neural  folds.   B. Motor  roots  grow  out  dorsally  from  the  cord.   C. The  nervous  system  originates  from  the  ectoderm.   D. Both  b  and  c   E. All  of  the  above     8. Which   of   the   following   is   the   counterpart   of   the   mouth   cavity   during   the   embryonic  stage?     A. Epimere   B. Proctodeum   C. Neural  crest   D. Stomodeum   E. Hypomere       9. NOT  true  about  gastrulation:     A. The   gastrula   consists   of   an   outer   layer   of   ectoderm   from   cells   of   the   animal  hemisphere.   B. At   the   end   of   gastrulation,   the   former   lower   end   of   the   axis   then   at   the   completed  blastopore  marks  the  posterior  the  end  of  the  future  animal.   C. After  gastrulation  major  differentiation  of  the  embryo  begins.   D. All  of  the  above   E. None  of  the  above     10. The  notochord  gives  rise  to  which  of  the  following?     A. Bile  duct   B. Smooth  muscles  of  the  gut   C. Excretory  organs   D. Both  b  and  c   E. All  of  the  above     11. Which   of   the   following   processes   forms   a   ring   of   involuting   tissue,   moves   over  and  increasingly  encloses  the  yolk-­‐laden  vegetal  hemisphere?     A. Cleavage   B. Epiboly   C. Invagination   D. Gastrulation   E. None  of  the  above              

12. Which  of  the  following  statements  is/are  NOT  true?     A. The   outer   surface   of   the   optic   vesicle   becomes   concave   by   invagination   and  forms  the  retina.   B. The   upper   most   mesoderm   is   called   hypomere   at   the   either   side   of   the   nerve  tube  and  notochord  and  forms  the  somites.   C. The   ectoderm   of   the   primitive   gut   becomes   the   lining   of   the   digestive   tract.   D. Both  b  and  c   E. All  of  the  above     13. In   each   stage   of   embryonic   development,   different   germ   layers   are   formed.   Which  of  the  following  stages  correctly  matches  the  germ  layers?     A. Blastula:  hypomere,  mesomere,  epimere   B. Gastrula:  neural  folds,  neural  crests,  neural  tubes   C. Notochord:  ectoderm,  mesoderm,  endoderm   D. All  of  the  above   E. None  of  the  above     14. Which  of  the  following  statements  is/are  TRUE?     A. Cleavage   of   the   zygote   forms   the   blastomeres   with   an   equal   number   of   chromosomes.   B. Involution   of   cells   away   from   the   blastopore   leads   to   the   formation   of   archenteron.   C. The  entoderm  is  derived  from  the  cells  of  the  vegetal  hemisphere.   D. Both  b  and  c   E. All  of  the  above     15. Peacocks   are   well   known   for   their   feathers   which   are   of   crescent   sheens   of   blue   and   green.   These   external   coverings   of   peacocks   are   a   derivative   of   which  germ  layer?     A. Ectoderm   B. Mesoderm   C. Endoderm   D. Entoderm   E. Chordamesoderm     16. If   an   abnormality   in   embryonic   development   occurred   in   the   notochord,   which  of  the  following  might  happen?     A. The  developing  animal  might  be  blind.   B. The  developing  animal  might  not  have  a  patent  anus.   C. The  developing  animal  might  have  soft,  brittle  and/or  weak  vertebrae.   D. Both  b  and  c   E. All  of  the  above     17. Which  of  the  following  statements  is/are  correct?     A. Sclerotomes  give  rise  to  voluntary  muscles.   B. The  endoderm  gives  rise  to  the  linings  of  the  digestive  tract.   C. The  mesoderm  gives  rise  to  the  trachea.   D. The  hindbrain  gives  rise  to  the  diencephalon.   E. The  ectoderm  gives  rise  to  the  larynx.          

Answer key: 1. B 2. A 3. D 4. E 5. B 6. C 7. B 8. D 9. E 10. D 11. B 12. D 13. E 14. E 15. A 16. D 17. B