Systems and Models

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TOPIC 1

• Systems and Models

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• IB Material Calculations
  TOK Link ICT Link

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1.1.1 Concept and characteristics of a system

• A system is a collection of well-organised and
  well-integrated elements with perceptible
  attributes which establish relationships among
  them within a defined space delimited by a
  boundary which necessarily transforms energy for
  its own functioning.
• An ecosystem is a dynamic unit whose organised
  and integrated elements transform energy which is
  used in the transformation and recycling of
  matter in an attempt to preserve its structure
  and guarantee the survival of all its component
  elements.
• Although we tend to isolate systems by delimiting
  the boundaries, in reality such boundaries may
  not be exact or even real. Furthermore, one
  systems is always in connection with another
  system with which it exchanges both matter and
  energy.
• TOK Link Does this hold true for the Universe?

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System B
Boundary
Relationships
E 3
E 1
E 2
Systems A
System C
Elements
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A natural system Ecosystem
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1.1.2 Types of systems (1)

• There are three types of systems based on
• whether they exchange energy and/or matter
• Isolated System
• It exchanges neither energy nor matter
• Do isolated systems exist?

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1.1.2 Types of systems (2)

• Closed System
• Energy System
  Energy
• It only exchanges energy.

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1.1.2 Types of systems (3)

• Open System
• Energy
  Energy
• System
• Matter
  Matter
• It exchanges both energy and matter.

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Understanding of 1st 2nd laws of thermodynamics
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1.1.4 Laws of Thermodynamics

• 1st Law of Thermodynamics
• The first law is concerned with the conservation
  of energy and states that energy can not be
  created nor destroyed but it is transformed from
  one form into another.
• With no energy transformation there is no way to
  perform any type of work.
• All systems carry out work, therefore all systems
  need to transform energy to work and be
  functional.

In any process where work is done, there has
been an energy transformation.
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First Law of Thermodynamics

• 
  ENERGY 2
• 
  PROCESS
• ENERGY 1 (WORK)
• 
  ENERGY 3

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Photosynthesis an example of the First Law of
Thermodynamics Energy Transformation
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Photosynthesis and the First Law of Thermodynamics

• 
  Heat Energy
  
• Light Energy
• 
  Chemical Energy

Photosynthesis
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The 2nd Law of Thermodynamics

• The second law explains the dissipation of energy
  (as heat energy) that is then not available to do
  work, bringing about disorder.
• The Second Law is most simply stated as, in any
  isolated system entropy tends to increase
  spontaneously. This means that energy and
  materials go from a concentrated to a dispersed
  form (the capacity to do work diminishes) and the
  system becomes increasingly disordered.

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Life and Entropy

• Life, in any of its forms or levels of
  organization, is the continuous fight against
  entropy. To keep order, organization and
  functionality, living organisms must used energy
  and transform energy.
• Living organisms use energy continuously in order
  to maintain everything working properly. If
  something is not working properly, living
  organisms must make adjustments so as to put
  things back to normal. This is done by negative
  feedback mechanism.
• What is really life? What do we live for? What is
  out purpose?

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The Second Law of Thermodynamics can also be
stated in the following way

• In any spontaneous process the energy
  transformation is not 100 efficient, part of it
  is lost (dissipated) as heat which, can not be
  used to do work (within the system) to fight
  against entropy.
• In fact, for most ecosystems, processes are on
  average only 10 efficient (10 Principle), this
  means that for every energy passage
  (transformation) 90 is lost in the form of heat
  energy, only 10 passes to the next element in
  the system.
• Most biological processes are very inefficient in
  their transformation of energy which is lost as
  heat.
• As energy is transformed or passed along longer
  chains, less and less energy gets to the end.
  This posts the need of elements at the end of the
  chain to be every time more efficient since they
  must operate with a very limited amount of
  energy.
• In ecological systems this problem is solved by
  reducing the number of individuals in higher
  trophic levels.

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Combustion Cell Respiration two examples that
illustrate the 1st and the 2nd laws of
Thermodynamics
Chemical Energy (sugar)
100 J
100 J
Chemical Energy (petrol)
ATP
PROCESS Combustion 20 J
PROCESS Cell Respiration 40 J
Heat Energy
60 J
Heat Energy
80 J
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The Second Law of Thermodynamics in numbers The
10 Law

• Heat Heat
  Heat
• 900 J 90 J
  9 J
• Energy 1 Process 1 Process 2
  Process 3
• 1000 J 100 J 10 J
  1 J
• J Joule SI Unit of Energy
• 1kJ 1 Kilo Joule 1000 Joules

For most ecological process, theamount of energy
that is passed from one trophic level to the next
is on average 10.
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• (d) Calculate the percentage () of the solar
  energy received by plants which remain available
  for herbivores?
  
  2
• (e) Which energy transformation chain is more
  efficient? Support your answer with relevant
  calculations.
  
  3

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Systems

• 1. Which row contains correct statements about
  exchanges between open and closed systems and
  their surroundings?
• Open system Closed system
• A. Exchanges matter but not energy Exchanges
  neither matter nor energy
• B. Exchanges matter but not energy Exchanges
  energy but not matter
• C. Exchanges energy but not matter Exchanges
  neither matter nor energy
• D. Exchanges matter and energy
  Exchanges energy but not matter

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Thermodynamics

• 2. The change in a systems internal energy is
  equal to the energy absorbed by the system minus
  the energy released into its surroundings. This
  statement best illustrates
• A. the law of conservation of mass.
• B. the first law of thermodynamics.
• C. the second law of thermodynamics.
• D. the third law of thermodynamics.

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Negative Feedback

• 3. Which is an example of negative feedback?
• A. An increase in air temperature increases the
  rate of melting of the Earths ice caps, thus
  decreasing the reflection of solar radiation.
• B. An increase in a herbivore population,
  leading to overgrazing and thus to a decline in
  the herbivore population.
• C. An increase in human birth rate compared with
  death rate leading to exponential increase in the
  human population.
• D. A loss of vegetation leads to soil erosion
  and thus further loss of vegetation occurs.

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Transfer Process

• 4. Which of the following is a transfer process /
  are transfer processes?
• I. Deposition of sand by waves on beaches
• II. Organic matter entering the ocean
• III. Decomposition of organic matter at the
  bottom of a lake
• IV. Run-off of water from land to rivers
• A. I and IV only
• B. III only
• C. I, II and IV only
• D. I, II, III and IV

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Photosynthesis and the 2nd law of Thermodynamics
What is the efficiency of photosynthesis?
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Primary Producers and the 2nd law of
Thermodynamics
(Output)
(Output)
(Output)
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Consumers and the 2nd law of Thermodynamics
How efficient is the cow in the use of the food
it takes daily?
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The Ecosystem and the 2nd law of Thermodynamics
What determines that some ecosystems are more
efficient than others?
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500
0.75
10,000
1000
100
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11.25
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Sealevel Changes
The graph below shows changes in the sea level on
the island of Oahu in the Hawaiian Islands,
Pacific Ocean, over the last century. Zero
represents the mean sea level in 1950. (a)
Describe and discuss possible explanations for
the shape of the curve in the graph.
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IB Question
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IB Question
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IB Question
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IB Question
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1.1.5 The Steady State

• The steady state is a common property of most
  open systems in nature whereby the system state
  fluctates around a certain point without much
  change of its fundamental identity.
• Static equilibrium means no change at all.
• Dynamic equilibrium means a continuous move from
  one point to another with the same magnitude, so
  no net change really happens.
• Living systems (e.g. the human body, a plant, a
  population of termites, a community of plants,
  animals and decomposers in the Tropical
  Rainforest) neither remain static nor undergo
  harmonic fluctuations, instead living systems
  fluctuate almost unpredictably but always around
  a mid value which is called the steady state.

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Static Equilibrium
STATE OF THE SYSTEM
Dynamic Equilibrium
Steady State
TIME
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1.1.6 Positive and Negative Feedback Mechanisms

• Natural systems should be understood as
  super-organisms whose component elements react
  against disturbing agents in order to preserve
  the steady state that guarantees the integrity of
  the whole system.
• The reaction of particular component elements
  of the systems againts disturbing agents is
  consider a feedback mechanism.
• Feedback links involve time lags since
  responses in ecosystems are not immediate!

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Positive Feedback
Sun

• Positive feedback leads to increasing change in a
  system.
• Positive feedback amplifies or increases change
  it leads to exponential deviation away from an
  equilibrium.
• For example, due to Global Warming high
  temperatures increase evaporation leading to more
  water vapour in the atmosphere. Water vapour is a
  greenhouse gas which traps more heat worsening
  Global Warming.
• In positive feedback, changes are reinforced.
  This takes ecosystems to new positions.

Atmosphere
Water Vapour


Global
Heat Energy
Evaporation
Warming


Oceans
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Negative Feedback
Population of Lynx
-
-

• Negative feedback is a self-regulating method of
  control leading to the maintenance of a steady
  state equilibrium.
• Negative feedback counteracts deviations from the
  steady state equilibrium point.
• Negative feedback tends to damp down, neutralise
  or counteract any deviation from an equilibrium,
  and promotes stability.

Population of Hare
In this example, when the Hare population
increases, the Lynx population increases too in
response to the increase in food offer which
illustrates both Bottom-Up regulation and
Positive Feedback. However, when the Lynx
population increases too much, the large number
of lynxes will pray more hares reducing the
number of hares. As hares become fewer, some
lynxes will die of starvation regulating the
number of lynx in the population. This
illustrates both Top-Down and negative Feedback
regulation.
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Negative feedback an example of population
control
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Positive Negative Feedback

• 
  Population 1
• Climate Food
  Population 2
• -
• 
  Population 3

-

-
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Positive Negative Feedback

• Food
  Population

Positive feedback
Negative feedback
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Negative or Positive ?

• Climate
• 
  Disease
• Food
  
• P1 P 2
  P3
• 
  

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Bottom-Up Top-Down Control

• In reality, ecosystems are controlled all the
  time by the combined action of Bottom-Up and
  Top-Down mechanisms of regulation.
• In Bottom-Up regulation the availability of soil
  nutrients regulate what happens upwards in the
  food web.
• In Top-Down regulation the population size
  (number of individuals) of the top carnivores
  determines the size of the other populations down
  the food web in an alternating way.

Plants
Ocean Food Webs - Bottom Up vs Top Down.flv Food
Web Bottom-Up Top-Down Middle Control
Worksheet.doc
Nutrient pool of the Soil
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Positive and Negative Feedback
?

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State of the Ecosystem
-

S2
S1
Time
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1.1.7 Transfer and Transformation Processes

• Transfers normally flow through a system from one
  compartment to another and involve a change in
  location. For example, precipitation involves the
  change in location of water from clouds to sea or
  ground. Similarly, liquid water in the soil is
  transferred into the plant body through roots in
  the same liquid form.
• Transformations lead to an interaction within a
  system in the formation of a new end product, or
  involve a change of state. For example, the
  evaporation of sea water involves the absorption
  of heat energy from the air so it can change into
  water vapour. In cell respiration, carbon in
  glucose changes to carbon in carbon dioxide.
  Ammonia (NH3) in the soil are absorbed by plant
  roots and in the plant nitrates are transformed
  into Amino acids. During photosynthesis carbon in
  the form of CO2 is changed into carbon in the
  form of Glucose (C6H12O6).These are just some
  example of transformations.

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1.1.8 Flows and Storages

• Flows are the inputs and outputs that come in and
  out between component elements in a system. This
  inputs and outputs can be of energy or quantities
  of specific substances (e.g. CO2 or H2O).
• Storages or stocks are the quantities that remain
  in the system or in any of its component elements
  called reservoirs.
• For example, in the Nitrogen Cycle, the soil
  stores nitrates (stock) (NO3-) however some
  nitrates are taken away as such by run-off water
  and absorbed by plant roots (output flows) but at
  the same time rainfall brings about nitrates,
  human fertilization and the transformation of
  ammonia (NH3) in to nitrates maintain the nitrate
  stock in soil constant under ideal conditions.

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• http//bcs.whfreeman.com/thelifewire/content/chp58
  /5802004.html

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IB Question
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O2
CO2
A simple model of an aquarium
Heat
CO2
Air
O2
CO2
O2
Primary Producers
Herbivorous animals
Aq Plant 1
Aq Plant 2
Carnivorous animal
Snail
Light
Algae
Flea
Phytoplankton
Heat
NO3
CO2
O2
Water
NO3
Decomposers
DOM
Mud
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Transfer, transformation, flows and storages(A
qualitative model)
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Transfer, transformation, flows and storages
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Transfer, transformation, flows and storages

• http//bcs.whfreeman.com/thelifewire/content/chp58
  /5802001.html

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• What can you identify in a
• plant?
• Transfer
• Transformation
• Flows
• Storage

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1.1.9 Quantitative Models

• A model is an artificial construction designed to
  represent the properties, behaviour or
  relationships between individual parts of the
  real entity being studied y order to study it
  under controlled conditions and to make
  predictions about its functioning when one or
  more elements and /or conditions are changed.
• A model is a representation of a part of the real
  world which helps us in ex situ studies.
• For example, the Carbon Cycle on the next slide
  is a quantitative model showing how carbon flows
  from one compartment to another in our planet.
  The width of the arrows are associated to the
  amount of carbon that is flowing. Figures next or
  on top of arrows indicate the amount of carbon in
  the flow. Similarly, figures inside boxes of
  compartments show the stocks or storages of
  carbon in each compartment.

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A quantitative model(The Carbon Cycle)
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A simplified model on how the ecosystem works

• For an entire ecosystem to be in steady state, or
  for one of its components to be in steady state,
  the following must be achieved

The Steady State condition
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ES-Practice-Model Making Pastoral System in
Angola.pdf
IB Question
MODEL MAKING PASTORAL SYSTEM IN ANGOLA.ppt
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Models can be used to make predictions
The following model tries to explain the
ecological behaviour of a human communities.
MODELLING SYSTEMS Handout.doc
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1.10 Strengths and Limitations of Models

• A model is a representation of part or the
  totality of a reality made by human beings with
  the hope that models can help us (i) represent
  the structural complexity of the reality in a
  simpler way eliminating unnecessary elements that
  create confusions, (ii) understand processes
  which are difficult to work out with the
  complexity of the real world, (iii) assess
  multiple interaction individually and as a whole
  (iv) predict the behaviour of a system within the
  limitations imposed by the simplification
  accepted as necessary for the sake of the
  understanding.
• Models are simplifications of real systems. They
  can be used as tools to better understand a
  system and to make predictions of what will
  happen to all of the system components following
  a disturbance or a change in any one of them. The
  human brain cannot keep track of an array of
  complex interactions all at one time, but it can
  easily understand individual interactions one at
  a time. By adding components to a model one by
  one, we develop an ability to consider the whole
  system together, not just one interaction at a
  time. Models are hypotheses. They are proposed
  representations of how a system is structured,
  which can be rejected in light of contradictory
  evidence.
• No model is a 'perfect' representation of the
  system because, as mentioned above, all models
  are simplifications and in some cases needed over
  simplifications. Moreover, human subjectivity may
  lead to humans to make models biased by scholar
  background, disregard of the relevance of some
  components or simply by a limited perception or
  understanding of the reality which is to be
  modeled.