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# Ess Topic 1 - Systems and Models

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### Ess Topic 1 - Systems and Models

1. 1. These  notes  correspond  with  pages  69-­‐90  in  the  IB  ESS  Course  Companion. 1.1.1  Outline  the  Concept  and  Characteris4cs  of  Systems A) a  system  is  deﬁned  as  “an  assemblage  of  parts  and  their  rela<onship  forming  a  func<oning  en<rety   or  whole”  (p.70) B) examine  the  parts  of  the  system  AND  how  all  the  parts  work  together C) The  systems  approach: 1. Specializa4on: a) system  is  divided  into  smaller  parts b) allows  more  concentra<on  on  each  individual  part 2. Grouping: a) group  related  disciplines  or  sub-­‐disciplines b) avoids  crea<ng  greater  complexity  with  more  specializa<on  (In  other  words,  it's  easier  to  study   a  system  by  grouping  many  small  parts  and  concentra<ng  on  ﬁguring  out  the  rela<onships  of   the  groups,  rather  than  the  individual  parts.) 3. Coordina4on: a) interac<ons  among  parts  within  a  group  must  be  coordinated b) interac<ons  among  groups  must  be  coordinated  to  work  together 4. Emergent  proper4es: a) why  the  system  as  a  whole  is  greater  than  the  sum  of  its  parts. b) the  interac<ons  of  the  parts  create  something  they  could  not  produce  independently. c) ex:  two  forest  stands  may  contain  the  same  tree  species,  but  the  spa<al  arrangement  and  size   structure  of  the  individual  trees  will  create  diﬀerent  habitats  for  wildlife  species.  In  this  case,   an  emergent  property  of  each  stand  is  the  wildlife  habitat. D) all  systems  have... 1. inputs 2. outputs 3. ﬂows 4. storages  of  maQer  and/or  energy 5. processes  (transfers  and  transforma<ons,  below) 6. boundaries E) There  are  2  major  components  (parts)  of  a  system: 1. Elements a) measurable  things  that  can  be  linked  together b) examples:  trees,  shrubs,  herbs,  birds,  and  insects  (stuﬀ  we  can  count,  measure  and  weigh) 2. Processes a) change  elements  from  one  form  to  another b) may  also  be  called  ac<vi<es,  rela<ons,  or  func<ons c) examples:  growth,  mortality,  decomposi<on,  and  disturbances  (what  happens  to  the  elements,   or  what  the  elements  do) ESS Topic 1.1 - The Systems Approach to Science
2. 2. 1.1.2  Apply  the  systems  concept  on  a  range  of  scales. ***  The  range  must  include  a  small-­‐scale  local  ecosystem,  a  large  ecosystem  such  as  a  biome,  and  Gaia   as  an  example  of  a  global  ecosystem. A. Nested  Systems  (Hierarchies) 1. smaller  systems  or  subsystems  within  larger  systems,  which  may  in  turn  be  nested  in  s<ll  larger   systems 2. higher  up  in  the  hierarchy  =  greater  complexity 3. can  be  very  small  (atomic)  or  large  (intergalac<c)  scales 4. ex:  ﬁsh  >  coral  reef  ecosystem  >  ocean  >  Earth  >  solar  system  >  galaxy  >  universe   Source:  hKp://silvae.cfr.washington.edu/ecosystem-­‐management/Systems.html B) systems  may  be  living  or  non-­‐living  and  on  any  scale  from  large  (a  biome,  the  atmosphere)  to  small   (a  cell)   C) iden<fy  the  components  of  these  sample  systems: 1. cell 2. bicycle 3. automobile 4. home 5. oﬃce/school 6. computer 1.1.3  Deﬁne  the  terms  open  system,  closed  system  and  isolated  system. A) Open  systems:  exchange  both  maQer  and  energy  with  their  surroundings       ex:  almost  all  ecosystems B) Closed  systems:  exchange  energy  but  not  maQer  with  their  surroundings     ex:  water  cycle.  E  from  the  Sun  is  imported,  but  water  stays  on  Earth C) Isolated  systems:  exchange  neither  energy  nor  maQer  with  their  surroundings       ex:  rare  in  nature,  usually  only  found  in  controlled  lab  experiments 1.1.4  Describe  how  the  ﬁrst  and  second  laws  of  thermodynamics  are  relevant  to  environmental  systems A) First  Law  of  Thermodynamics:  energy  is  neither  created  nor  destroyed   1. total  energy  remains  constant 2. the  form  of  the  energy  can  change  (it  can  be  transformed  from  poten<al  to  electrical,  for   example) 3. aka  “Law  of  Conserva<on  of  Energy”   B) Second  Law  of  Thermodynamics:  entropy  increases  over  <me 1. energy  transforma<ons  are  not  100%  eﬃcient,  so  the  availability  of  energy  to  do  work   diminishes 2. entropy:  spreading  out  or  disorganiza<on  of  energy 3. see  Fig.  4.12  on  p.75   1.1.5  Explain  the  nature  of  equilibria. A) equilibrium  =  one;  equilibria  =  more  than  one  equilibrium B) steady-­‐state  equilibrium 1. open,  living  systems ESS Topic 1.1 - The Systems Approach to Science
3. 3. 2. no  long-­‐term  changes  but  many  short-­‐term  changes 3. the  overall  balance  of  the  system  remains  stable 4. almost  all  open  systems  in  nature C) returns  to  original  equilibrium  ader  disturbance  (i.e.  stable) D) sta4c  equilibrium 1. closed,  non-­‐living  systems 2. no  change  over  <me 3. no  change  at  all;  stagnant;  status  quo 4. disturbance  creates  a  new,  diﬀerent  equilibrium  (i.e.  unstable) 5. rare  in  nature  and  is  usually  created  in  a  laboratory  seeng  for  comparison  with  'real'  natural   systems ESS Topic 1.1 - The Systems Approach to Science
4. 4. 1.1.6  Deﬁne  and  explain  the  principles  of  posi4ve  feedback  and  nega4ve  feedback. A) Natural  systems  regulate  themselves  through  feedback  systems.  Feedback  always  involves  <me   lags. B) feedback  mechanisms  either  change  a  system  to  a  new  state  or  return  it  to  the  original  state  ader  a   disturbance C) posi4ve  feedback  -­‐   1. a  change  in  the  state  of  a  system  causes  even  greater  changes  in  the  system  so  that  it  moves   further  and  further  from  the  original  equilibrium 2. reinforces  &  accelerates  change  (devia<on  further  and  further  from  the  'norm') 3. early  changes  lead  to  greater  and  greater  changes  over  <me 4. think  of  the  'snowball'  eﬀect:  popula<on  growth,  recurring  interest  on  an  investment 5. “in  a  system,  those  changes  which  serve  to  increase  the  eﬀect  (source:  www.tui<on.com.hk/ geography/p.htm)   D) nega4ve  feedback 1. a  change  in  the  system  which  oﬀsets  or  neutralizes  changes  and  returns  the  system  to  its   original  state  or  equilibrium   2. counteracts  and  diminishes  devia<on  from  the  'norm';  it  has  a  stabilizing,  self-­‐regula<ng  eﬀect   on  a  system   3. a  form  of  control  within  the  system  to  keep  it  stable,  i.e.  steady-­‐state  equilibrium 4. ex:  predator-­‐prey  rela<onships E) study  the  examples  on  pp.  79-­‐81  of  the  book  for  a  beQer  understanding 1.1.7  Describe  transfer  and  transforma4on  processes. A) maQer  and  energy  both  ﬂow  through  systems 1. energy  tends  to  move  through  the  system  (input  >  storage  >  output) 2. maQer  tends  to  cycle  within  the  system  (think  water,  carbon,  and  nitrogen  cycles) B) transfers  do  NOT  change  the  form  of  energy  or  maQer 1. movement  of  maQer  through  organisms 2. movement  of  maQer  or  energy  from  one  place  to  another   3. examples  on  p.83 C) transforma4ons  change  the  form  of  energy  or  maQer 1. require  more  energy  than  transfers  because  they’re  more  complex 2. changes  the  form  of  energy  or  the  state  of  maQer a. ex:  a  farmer  bringing  animal  manure  to  his  ﬁelds  is  a  transfer  process.  The  transforma<on   process  happens  when  the  manure  decomposes,  its  nutrients  become  part  of  the  soil   matrix  and  are  incorporated  into  the  physical  structure  of  food  crops  growing  there. b. examples  on  p.83   1.1.8  Dis4nguish  between  ﬂows  (inputs  and  outputs)  and  storages  (stock)  in  rela4on  to  systems.   A) ﬂows  =  movement  through  or  within  the  system 1. energy  tends  to  ﬂow  through  the  system  (input  >>  storage  >>  output) 2. maQer  cycles  con<nuously  within  the  system B) storages  =  maQer/energy  remain  in  the  system 1. solar  radia<on  converted  to  glucose  during  photosynthesis  is  stored  as  chemical  energy    in  the   bonds  within  plants’  cells 2. bioaccumula<on  and  biomagniﬁca<on  of  heavy  metals  and  POP’s C) see  Fig.  4.24-­‐27  on  pp.  83-­‐85   ESS Topic 1.1 - The Systems Approach to Science
5. 5. 1.1.9  Construct  and  analyze  quan4ta4ve  models  involving  ﬂows  and  storages  in  a  system. D) Modeling  Systems 1. types  of  models   a. physical  models b. sodware  simula<ons c. mathema<cal  formulas d. diagrams 2. advantages  of  models a. simpler  than  reality  so  easier  to  study  and  understand b. can  change  the  model  without  disastrous  eﬀects   c. useful  for  predic<ng  what  might  happen  under  diﬀerent  circumstances   3. disadvantages a. may  be  incomplete,  so  results  may  not  be  accurate  or  reliable b. liable  to  human  error 4. Ac<vity:  Iden<fying  inputs,  outputs,  and  stock  within  an  ecosystem. a. Use  the  ecosystem  from  your  elements  and  processes  ac<vity  in  1.1.1  above  to  develop  a   ﬂow  chart  showing  inputs,  outputs,  ﬂows,  and  storage  within  that  ecosystem. b. Use  block  arrows  to  show  the  direc<on  of  ﬂow. c. The  size  of  the  arrow  should  reﬂect  the  magnitude  of  that  ﬂow  (bigger  arrow  =  larger  ﬂow). d. The  ﬂow  chart  should  include  adjacent  systems  where  inputs  come  from  and  outputs  go. e. Be  sure  to  clearly  describe  and  label  every  component  of  your  ecosystem. ESS Topic 1.1 - The Systems Approach to Science