Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...
Topic 1 systems and models
1. 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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3. A natural system = Ecosystem
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4. 1.1.2 Types of systems (1)
There are three types of systems based on
whether they exchange energy and/or matter:
Isolated System
System
It exchanges neither energy nor matter
Do isolated systems exist? If not, why then we have
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thought about them?
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5. 1.1.2 Types of systems (2)
Closed System
Energy
System
Energy
It only exchanges energy.
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6. 1.1.2 Types of systems (3)
Open System
Energy
Energy
System
Matter
Matter
It exchanges both energy and matter.
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7. 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”.
* In any process where work is done, there
has been an energy transformation.
• 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.
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8. First Law of Thermodynamics
ENERGY 2
ENERGY 1
PROCESS
(WORK)
ENERGY 3
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10. Photosynthesis: an example of the First Law of
Thermodynamics: Energy Transformation
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11. Photosynthesis and the First Law of
Thermodynamics
Heat Energy
Light Energy
Photosynthesis
Chemical Energy
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12. • 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 Guru/ESS/System & Models-Chapter
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disordered.
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13. Life and Entropy
• Life, in any of its forms or levels
of organization, is the continuous
fight against entropy. In order to
fight against entropy and keep
order, organization and
functionality, living organisms
must used energy and transform
it so as to get the energy form
most needed.
• 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 (we`ll discuss this
later).
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14. 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 Models-Chapter
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trophic levels.
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15. Combustion & Cell Respiration: two examples that
illustrate the 1st and the 2nd laws of Thermodynamics
Chemical Energy
Chemical Energy
(petrol)
(sugar)
100 J
100 J
ATP
PROCESS
Combustion
20 J
PROCESS
Cell Respiration
40 J
Heat Energy
60 J
Heat Energy
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16. The Second Law of Thermodynamics
in numbers: The 10% Law
For most ecological process, theamount of energy that is passed from one
trophic level to the next is on average 10%.
Heat
900 J
Energy 1
1000 J
Heat
90 J
Process 1
100 J
Heat
9J
Process 2
10 J
Process 3
1J
J = Joule SI Unit of Energy
1kJ = 1 Kilo Joule = 1000 Joules
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19. Photosynthesis and the 2nd law of Thermodynamics
What is the efficiency of photosynthesis?
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20. Primary Producers and the 2nd law of
Thermodynamics
(Output)
(Output)
(Output)
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21. How efficient is the cow
Consumers and the
2nd law of Thermodynamics in the use of the food it
takes daily?
Respiration
2000 kJ.day-1
10% for growth
2850 kJ.day-1
Food Intake
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kJ.day-1
Urine and
Faeces
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22. The Ecosystem and the 2nd
law of Thermodynamics
Heat
Heat
Heat
Heat
Heat
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