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ESSAY ON STELLA

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  • 1. SSI3013 : ICT IN SCIENCE TITLE : MODELLING AND STIMULATION BY USING STELLA GROUP: C PREPARED BY: NAME ID NO. PHONE NO. NUR ASHIKIN BINTI ALIAS D20101037459 012-3139521LECTURER’S NAME: MR. AZMI BIN IBRAHIMDUE DATE : 3rd DECEMBER 2012
  • 2. TEACHING AND LEARNING BASED ON MODELLING AND SIMULATION Nowadays, computer technology has evolved dramatically over the years and hassignificantly changed the society. As technology advances, it transform and improves thesociety. The revolution of computer technology changed the way of people thinkingespecially for the computer system users, administrators and designers. Generally, theyhave their own goal of highest performance at lowest cost. Here, modelling and simulation ofsystem design is a good preparation to deal with real work. So now, what is modelling? Whatis simulation? How they work? What type of problems that suitable for simulation? How toselect simulation software? What are the benefits and disadvantages of modelling andsimulation? Everyone are keep on asking about it. Modelling and simulation is the process of producing a model over the time todevelop data as a basic to manage or technical decisions that involved emulators,prototypes, simulators and stimulators either statically or over. Modelling and simulation areoften used interchangeably. A model is a representation of an object, a system or idea insome form of other than that of the entity itself. The model is looks similar but it is moresimpler than the system it represents. One of the purposes of a model is to enable us toanalyse the effect of changes to the system. On the other hand, the model should be closeapproximate to the real system and do not to be so complicated because it might difficult tobe understand it. A good model is the one that can differentiate between realism and simplicity. Animportant issue in modelling is model validity. Model validation techniques includesstimulating the model under known input conditions and compared the model with systemoutput. There are various types of models which are physical model (scale models,prototype plants) and mathematical model (analytical queueing models, linear programs andsimulation). Generally, a model that intend for a simulation study is a mathemical model thatdevelop with the help of simulation software. Mathematical model are includes deterministicwhere the input and ouput variables are fixed values, or stochastic (at least one of the ouputvariables is probabilistic), static (time is not included) or dynamic (time-varying interactionsamong the variables are included). Typically, simulation models are stochastic and dynamic. While, a simulation of a system is the operation of a model of the system which isrepresentation of that system. The model is amenable to manipulation which would beimpossible, too expensive or to impractical to perform on that system which it represents.The operation of the model can be studied and the properties concerning the behaviour ofthe actual system or its subsystem can be inferred. In its broadest sense, simulation alsoevaluate the performance of a system. Simulations is used before an existing system built
  • 3. which is to reduce the chances of failure to meet specifications and to optimize systemperformance. Simulators are collection of hardware and software which are used to mimicthe behaviour of some entity. The simulation is used widely nowadays in many fields suchas in education, industry and etc. In educational field, computer simulation is suitable to used in order relate theclassroom material with relevant experiences. It become one of the factor that contribute to amotivation of student’s success. Thus, the educator that apply simulation during classsession, they must be well understood to used it in order to motivate the students. Not onlythat, to successfully implement a computer simulation in classroom, educators also need toconsider ‘play’ factor which one of the most important motivators. This is because, simulationis a part of teaching model. What is the advantages of using these simulation? One of themis simulators can be used as an effective materials for teaching or demonstrating concepts ofa real system to the students. These particular true of simulators make an intelligent use ofcomputer graphics and animation. It dynamically shows the behavior and the relationship ofall the simulated system’s components so that the users are providing with a meaningfulunderstanding of the system’s nature. For example, for Physics teacher who want to teachabout circuit, by using simulation, the students can see what actually happened to the circuitand they become more understanding towards the dynamic circuit. Besides that, simulatorused also enable students to control either to speed up, slow down, stop or even reverse thesimulation to more understanding. Besides that, teaching with simulation method have the potential to engage studentsin ‘deep learning’ that empowers understanding as opposed to ‘suface learning’ which onlyrequires memorization. Deep learning is refer to the students that can learnt scientificmethods including doing the experiments and simulation. Here, simulation gives studentsconcentrate formats to think like a scientist. Not only that, by using simulation, we can adjustthe variables that being used in the model. So, it allows the students to change theparameter values and can observe what happens and they able to make a prediction. It alsoencourage students to participate actively since these type of instructional simulationscannot be passive learning. A well done simulation is constructed to include an extension toa new problem or new set of parameters that requires students to extend what they havelearned in an earlier context. Instead of advantages, there are disadvantages of the simulation. A disadvantage ofsimulation in comparison to exact mathematical methods is stimulation cannot be usednaturally to find an optimal solution. Simulation model often used to approach complexsystem analysis. However, there are many systems that cannot be modelled with
  • 4. mathematical equations. Besides that, simulation model also is quite expensive since theprocess must be well understood although we know that the simulation can help theprocess. The most expensive part is the collection of data for the simulation. The suitable software used for these Modelling and Simulation especially ineducation is STELLA which is a system thinking for Education and Research. STELLA offersa practical way to dynamically visualize and communicate how complex the systems andideas really work. STELLA is used to stimulate a system over the time, jump the gapbetween theory and the real world and also it enable students to creatively change thesystems. Moreover, STELLA teach students to look for a relationships and also it create aclear communication system inputs and outputs to demonstrate the outcomes. There aremany topics that can be construct by using STELLA. One of them is Predator-PreyDynamics. This topic is quiet familiar among the school’s student until the higher level ofstudy. Predator-prey DynamicsIntroduction: Community structure refers to the number and relative abundances of species in ahabitat which it changes over the time. Each community have a dynamic structure, reflectedin shifting patterns of biodiversity. Species interactions, as well as abiotic factors such asclimate and source of food will affect the the community structure. There are five type ofdirect species interactions in communities. Species interact in ways that can be beneficial,harmful, or have no effect on one another. The interaction will shifts the numbers andabundances of the species. Besides that, co-evolution is one of the the important parts of an organism’senvironment in other organisms. It occurs when the species are adapting to theenvironments, two or more organisms evolve together to show off their strength in thehabitat, organisms make use of other organisms by eating them and mating. At the sametime, organisms coevolve with many species due to the environment that consists of manytypes of organisms. Organisms have to adapt to form the relationship similar like they haveto adapt with any part of their environment. These adaptations cause changes in thedescendants which the better suited to take the advantage on the relationship and they may
  • 5. be entirely different species from their ancestors. Relationships that formed through co-evolution can be called symbiotic relationships. One of the symbiotic relationship is predator-prey interactions. Predator-prey interactions refers to the relative abundance of predator and preypopulations of a community which shift over the time in response to species interactions andchanging environmental conditions. Predators are consumers that gain energy and nutrientsfrom prey which are living organisms that predators capture, kill and eat. The quantity andtypes of prey species affect predator diversity and abundance, and predator types and thenumbers do the same for prey. The extent to which predators affect prey numbers dependson how individual predators respond to changes in prey density. Predator and prey areevolve together. The prey is part of the predators environment, and the predators also a partof prey’s environment. The predator will die if there is no food, so it evolves in order to eatthe prey. The characteristics of animals that can be a predators are it have high speed to runso that they can catch the prey quickly, it can stealth, it have ability to camouflage, it have agood sense of smell, sight, or hearing (to detect the location of the prey), it have highimmunity to against the preys poison, and also it have its own poison that used to kill theprey. As we know, the population of organisms does not remains constants. The number ofindividuals within a population changes sometimes dramatically from one time to to another.There are fluctuations that wide in variety organisms including algae, invertebrates, fish,frog, birds, and mammals such as rodents, large herbivores and carnivores. The resourcesthat available plays an important role to control the fluctuations. There are three models forresponses of predators to prey density. In a type I response, the proportion of prey killed isconstant, so the number killed in any given interval depends on the prey density. Forexample, the web spinning spiders and other passive predators. When the number of flies isincrease, there are more will be caught by the spider web. While, in a type II response, thenumber of prey killed is depend on the capacity of predators to capture, eat and digest theprey. As the prey density is increases, the rate of kills rises steeply at first because there aremany prey that they have to catch. However, the rate of increase become slow because theprey cannot handle all the prey in one time. For example is the wolf will not hunt on otheranimals till it finished eat and digested the caribou first. This is common in nature. This isfollowed by type III response where the number of predators kills increase slowly until theprey density exceed a certain level, then it rise rapidly and stop. These kind of response iscommon in nature with three conditions. The first is the predators are switched among theprey and it concentrate the efforts on the species. The second is the predators have to learn
  • 6. the best way to capture the prey. The third is when the number of hiding places for prey islimited. The number of predators increase when the prey density increases. When resources are limited, the population will decline because each individuals arecompete each other to get it. The bottom-up control helped the population around carryingcapacity. Besides that, the predation can also affect the size of prey population by act as thetop-down controller. Thus, the interaction between these two forms of population are worktogether to alter the population over the time. By knowing this, the ecologist can predict thelong term-effects of predation on a prey population. The presence of parasites and diseasealso affect the population dynamics. There are some cases where the time lag in the predator’s are response to the preydensity and cause a cyclic changes in abundance of predators and prey. If the prey densityare lower, the number of predators also reduce. Thus, the prey are in safe condition andhave increase in numbers, However, this situation gives opportunity to the predators toincrease in number and causes the prey decline and the cycle starts again. Based on predator-prey models, the building blocks of the bio-ecosystems arebiomasses are develop their resource masses. The species are compete and evolve eachother and disperse in order to survive. By depending on their specific setting of applications,the species can have the forms of resource-consumer, plant-herbivore, parasite-host, tumorcells (virus)-immune system. They also faced the general loss-win interaction and also canhave the applications out of the ecosystems. When there are competitive interactions, theyare often in some forms predator-prey interactions. The Lotka-Volterra model describes the interactions between two species in anecosystem which is a predator and a prey. This is shown the first-species model. Thepopulation changes and the predator population changes are describing by usingmathematical equations. As we know, the populations are always changing. The changesare may because of human interfering the food web or habitats or even human do notdisturbing the habitat, the population will naturally changes either goes up and down orfluctuate. One of the most famous example of population changes is the predator-preypopulation cycle of the showshoe hare and lynx. The snowshoe hare in North America is a common species of mammals that relatedto rabbit. Snowshoe hare is the smallest member of genus Lepus. It belongs to familyLeporidae. Generally, hares have longer ears, longer hind feet and even the tail is short, butit is more longer than rabbits. The used of name is always misapplied to particular species.
  • 7. The sizes of body of the hares is depend on the species which can helps to dissipate excessbody heat. Snowshoe hare have two colour pattern where throughout the summer, it will turnto brown and during winter, it turn into white so that it can get a better camouflage with thesnow. The snowshoe hares depends on grasses, berries, twigs, bark and leaves to survive.It have high rates of reproduction where there are multiple large litter are produced eachyear. The young hares are born fully furred and their eyes are open to enable it to hop for afew minutes after birth. Hares serves as a diets of carnivorous birds, mammals and reptiles.For human, hares provide food and fur. While lynx is a wild cat in north America which have similar looks like a large housecat with a short tail and prominent tufts on its ears. It belongs to family Felidae. It have longleg, large pawed cats with tufted ears, hairy soles and a broad, short head. There are coatsthat formed a bushy ruff on its neck with a cream colour that mottled with brown and black.The tip of the tail and the tufts of the ears are black in colour. During winter season, the fur isdense and soft till and is sought by human for trimming garments. Lynx is a nocturnal andsilent animals except for during mating season. It live alone or in small groups. It climbs andswim well and feed on birds and other small mammals. The Canada lynx are too depend onsnowshoe hare for food. The lynx lies in wait its favourite prey, snowshoe hare. When thereare hare, the lynx move, bounding from its cover and starts to chase the hare and trying toevade it adversary. Then, its population increases and decreases every 9 or 20 years whichrelative to the population of its prey. Lynx breed at the end of winter or early of springseason. There are four young is born after gestation period which is about two months. Lynxare very secretive and even experienced hunters rarely see one in the wild. Its rangeoverlaps with the snowshoe hare, on which it almost exclusively preys upon. So, howModelling and Simulation are apply in Predator-prey dynamics?
  • 8. Discussion: Graph 1 : The relationship between Snowshoe hare and Lynx In order to run the simulation, firstly, we have to set with the zero number of removalLynx. Since, there is no Lynx, so we can predict that there is no predation occur among Lynxand snowshoe hares. Based on the Graph 1, the interactions between Snowshoe hares andLynx are constant. This is show that the population of both species are stable. Lynx do notdisturbed the snowshoe hares population growth. Each snowshoe hares gives rise to aconstant number of offspring per year. In other words, there are no limiting factors thatinterfere the snowshoe hares population growth apart from lynx. Besides that, each lynx eatsa constant proportion of the snowshoe hares population per year. That’s mean that if wedoubling the snowshoe hares population, thus the number eaten per lynx also doubles. It isregardless on the size of snowshoe hare’s population. Lynx reproduction also is directlyproportional to snowshoe hares consumed. Another way to describe this is there are certainnumber of snowshoe hares consumed will results in one new predator or one preyconsumed will produces some fraction of a new predator. Moreover, there are constantproportion of the lynx population dies per year which are the death rate of lynx isindependent of the amount of food available. They live in peace, harmony and equilibrium.
  • 9. Graph 2Graph 3
  • 10. Next, we adjust the reading of the number Lynx harvest up to 200 (Graph 2) and wedoubled it into 400 (Graph 2). What can we predict that, as the number of snowshoe haresincrease, the number of Lynx also increase. So, Graph 2 and Graph 3 shows thepopulation’s growth and decline through time of both Lynx and Snowshoe hares. From thegraph, we can see that the snowshoe hares population leads the lynx population throughcycle. From the beginning, the lynx cannot detect a decrease in snowshoe haresimmediately, so it will experience the difficulties of finding prey. Due to the declining of foodsupply, starvation, mortality as well as difficulty to produce young are occurred, so it causethe lynx to response. However, the snowshoe hares does respond immediately to the Lynxdeclining numbers. There are more snowshoe hares are left alive because there are fewerLynx are catching, killing and eating fewer of them, but to increase in numbers, snowshoehares have to reproduce and it takes time so there is a lag in the response of eachpopulation to the changes that takes place in other. Graph 4 Lastly, the number of Lynx harvest is adjust up to 750, the maximum value. Theprediction can be made is there are higher number of hares will consumed due to the highnumber of Lynx harves. As the number of hares increase, Lynx also increased. From thegraph, we can see that the snowshoe hares population leads the lynx population through
  • 11. cycle. Suddenly, there are decline in hares population. This is may because of diet of haresdecrease that lead to hares die off and Lynx have to turn to other prey. The lynx are pickyand many starve to death, so there are lack of predators and allow the vegetation to growsback and the Snowshoe hare rejuvenates. Since there are more hares and nutritionavailable, the Lynx population grows and the cycle begins. However, it brings stress forhares and a downword spiral in their population like a roller coaster cycle. But, the lynxmaintain riding its up and down.Conclusion:The balance of natural processes is extremely delicate. They are affected by manyenvironmental and external factors such as food web, vegetation adaptations, trapping andprey preference that affect the population of Lynx.
  • 12. References:Randy L.Bell and Lara K. Smetana, retrieved athttp://cs.explorelearning.com/docs/tech_sec_science_chapter_3.pdf on 24th November,2012.http://www.cs.mun.ca/~donald/msc/node6.html retrieved on 15th November 2012.http://www.eg.bucknell.edu/~xmeng/Course/CS6337/Note/master/node1.html retrieved on15th November 2012.http://www.inf.utfsm.cl/~hallende/download/Simul-22002/Introduction_to_Modeling_and_Simulation.pdf retrieved on 7th November 2012.http://home.ubalt.edu/ntsbarsh/simulation/sim.htm#rintroduction retrieved on 7th November2012.http://www.systems-thinking.org/modsim/modsim.htm retrieved on 7th November 2012.http://en.wikipedia.org/wiki/Modeling_and_simulation retrieved on 7th November 2012.http://en.wikipedia.org/wiki/Computer_simulation retrieved on 7th November 2012.