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TOPIC 1

TOPIC 1. SYSTEMS AND MODELS (5 Hours). IB Material Calculations TOK Link ICT Link. 1.1.1 Concept and characteristics of a system.

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TOPIC 1

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  1. TOPIC 1 SYSTEMS AND MODELS (5 Hours)

  2. IB Material Calculations TOK Link ICT Link

  3. 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 boundarywhich necessarilytransforms energyfor 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?

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

  5. A natural system = Ecosystem

  6. 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 thought about them?

  7. 1.1.2 Types of systems (2) Closed System EnergySystemEnergy It only exchanges energy.

  8. 1.1.2 Types of systems (3) Open System Energy Energy System Matter Matter It exchanges both energy and matter.

  9. 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.

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

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

  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 disordered.

  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. What is really life? What do we live for? What is out purpose? Energy Entropy Life

  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 trophic levels.

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

  16. The Second Law of Thermodynamics in numbers: The 10% LawFor 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 3 1000 J 100 J 10 J 1 J J = Joule SI Unit of Energy 1kJ = 1 Kilo Joule = 1000 Joules

  17. (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] ……………………………………………………………………………………………… ……………………………………………………………………………………………… ………………………………………………………………………………………………

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

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

  20. Respiration 2000 kJ.day-1 10% for growth 565 kJ.day-1 Urine and Faeces 2850 kJ.day-1 Food Intake How efficient is the cow in the use of the food it takes daily? Consumers and the 2nd law of Thermodynamics

  21. Heat Heat Heat Heat Heat What determines that some ecosystems are more efficient than others? The Ecosystem and the 2nd law of Thermodynamics

  22. IB Question

  23. IB Question

  24. IB Question

  25. IB Question

  26. 1.1.5 TheSteadyState • 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”.

  27. STATE OF THE SYSTEM Static Equilibrium Dynamic Equilibrium Steady State TIME

  28. 1.1.6 Positive and NegativeFeedbackMechanisms 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!

  29. 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

  30. Population of Lynx Negative Feedback - - + • Negativefeedbackis a self-regulatingmethod of control leadingtothemaintenance of a steadystateequilibrium. • Negativefeedbackcounteractsdeviationsfromthesteadystateequilibriumpoint. • Negativefeedbacktendstodampdown, neutraliseorcounteractanydeviationfromanequilibrium, and promotesstability. 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.

  31. Negative feedback: an example of population control

  32. Positive & Negative Feedback Population 1 + Climate Food Population 2 - Population 3 + + - + -

  33. Positive & Negative Feedback Food Population Positive feedback Negative feedback

  34. Negative or Positive ? Climate Disease Food P1 P 2 P3

  35. 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

  36. Positive and Negative Feedback ? + - State of the Ecosystem - + S2 S1 Time

  37. 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.

  38. 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.

  39. http://bcs.whfreeman.com/thelifewire/content/chp58/5802004.htmlhttp://bcs.whfreeman.com/thelifewire/content/chp58/5802004.html

  40. IB Question

  41. A simple model of an aquarium CO2 O2 Heat CO2 O2 Air 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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