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?TOK Link: Does this hold true for the Universe? 1

E 1 E 2 E 3 Boundary Elements Relationships Systems A System B System C 2

A natural system = Ecosystem 3

1.1.2 Types of systems (1) 4

1.1.2 Types of systems (2) 5

1.1.2 Types of systems (3) Open System Energy Energy System System Matter Matter Matter Matter It exchanges both energy and matter. 6

1.1.4 Laws of Thermodynamics 1 st Law of Thermodynamics1 st Law of Thermodynamics conservation of energyThe 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. 7

First Law of Thermodynamics ENERGY 2 PROCESS ENERGY 1 (WORK) ENERGY 3 8

Photosynthesis: an example of the First Law of Thermodynamics: Energy Transformation 10

Photosynthesis and the First Law of Thermodynamics Heat Energy Light Energy Chemical Energy Photosynthesis 11

The 2nd Law of Thermodynamics 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. 12

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). Entropy Life Energy 13

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. The Second Law of Thermodynamics can also be stated in the following way: 14

Combustion & Cell Respiration: two examples that illustrate the 1st and the 2nd laws of Thermodynamics Heat Energy ATP Chemical Energy (petrol) Chemical Energy (sugar) PROCESS Combustion 20 J PROCESS Cell Respiration 40 J 100 J 80 J 60 J 15

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 Heat Heat 900 J 90 J 9 J Energy 1 Process 1 Process 2 Process J 100 J 10 J 1 J J = Joule SI Unit of Energy 1kJ = 1 Kilo Joule = 1000 Joules 16

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Photosynthesis and the 2 nd law of Thermodynamics What is the efficiency of photosynthesis? 19

Primary Producers and the 2 nd law of Thermodynamics (Output) (Output) (Output) 20

Consumers and the 2 nd law of Thermodynamics 10% for growth 2850 kJ.day -1 Food Intake Respiration 2000 kJ.day kJ.day -1 Urine and Faeces How efficient is the cow in the use of the food it takes daily? 21

The Ecosystem and the 2 nd law of Thermodynamics Heat 22

IB Question 23

IB Question 24