e-portfolio

1.0 Title :

Natural Selection Pressure Of Rabbits On A Specific Particular Area.

2.0 Aims :

1) To conduct an experiment using STELLA Software.

2) To know how to make the stimulation using STELLA Software.

3) To study how to integrate STELLA in teaching and learning process.

3) To understand natural selection pressure of rabbits on a specific area.

4) To study the relationship between the predator and prey.

3.0 Introduction

Simulation is the applying of the operation of a real-world process or system over time. The act of simulating something first requires that a model be developed, this model represents the key characteristics or behaviors of the selected physical or abstract system or process. The model represents the system itself, whereas the stimulation represents the operation of the system over time. Computer simulation is the discipline of designing a model of an actual theoretical physical system, executing the model on a digital computer, and analyzing the execution output. Stimulation is used in many contexts such as simulation of technology for performance optimization, safety engineering, testing, training, education, and video games. Training simulators include flight simulators for training aircraft pilots to provide them with a life like experience.

Simulation is also used with scientific modelling of natural systems or human systems to gain insight into their functioning. Simulation can be used to show the eventual real effects of alternative conditions and courses of action. Simulation is also used when the real system cannot be engaged, because it may not be accessible, or it may be dangerous or unacceptable to engage, or it is being designed but not yet built, or it may simply not exist. Key issues in simulation include acquisition of valid source information about the relevant selection of key characteristics and behaviours, the use of simplifying approximations and assumptions within the simulation, and fidelity and validity of the simulation outcomes. Simulation embodies the principle of learning by doing to learn about the system we must first build a model of some sort and then operate the model.

The use of simulation is an activity that is as natural as a child who role plays. Children understand the world around them by simulating with toys and figurines most of their interactions with other people, animals and objects. As adults, we lose some of this childlike behavior but recapture it later on through computer simulation. To understand reality and all of its complexity, we must build artificial objects and dynamically act out roles with them. Computer simulation is the electronic equivalent of this type of role playing and it serves to drive synthetic environments and virtual worlds. Less theoretically, an interesting application of computer simulation is to simulate computers using computers. In computer architecture, a type of simulator, typically called an emulator, is often used to execute a program that has to run on some inconvenient type of computer or in a tightly controlled testing environment.

One of the stimulation software is STELLA. STELLA is a computer program that is created by Robert Webb of Australia. It is a system thinking for education and research. Education and research are most exciting when student can move out of the lecture room and library and provide opportunity to create, experience and see. STELLA offers a practical way to dynamically visualize and communicate how complex systems and ideas really work. STELLA is one of the simulation software. STELLA can be use to stimulate a system over time. The stimulation made by teacher can be repeated many times. It is also can jump the gap between theory and the real world especially when teacher can show the experiment practically instead of by theory only. By using STELLA, students are enable to creatively change the systems. This is because STELLA provide a stimulation programme that enable the user to vary the data in order to get the difference result of their experiment.

By using this simulation software, teacher can teach students to look for relationships and see the big picture in it. Intuitive icon-based graphical interface simplifies model building. Stock and flow diagrams that provided in STELLA support the common language of systems thinking and provide insight into how system work. STELLA is also used to clearly communicate system inputs and outputs and demonstrate outcomes. Flight simulators and dashboards describe model components and facilitate manipulation. The output devices highlight the outcomes with warning flashers, text, graphs, tables and reports. Student will be able to understand the experiment more clearly and the teaching and learning process will be more fun. By using simulation in teaching process can help teacher to explain the experiment more clearly thus can increase student performance in the exam.

4.0 Results

In this model, foxes prey on rabbits. Foxes catch the slower rabbits, which favors an evolution over time toward faster rabbits. For the base case simulation the bias are set to 20.

Graph 1 : Graph of simulation with the bias speed set to 20 (normal).

Years	Average Speed Of Rabbits (ms)
5	6
10	12
15	18
20	24
25	24
30	24

From the graph, we can see that the x-axis in the simulation graph is the years and for the y-axis is the average speed of the rabbits. For the first five years, the average speed of the rabbits is constant. There are no increase in average speed of the rabbits yet as the rabbits still not evolved. Thus, in this phase, the rate of birth of the rabbits is lower to the rate of death rabbits. This is because, foxes prey on the rabbits causing the rate of birth of the foxes is greater than the rate of death of the foxes. In this first five years, foxes are able to catch and eat the rabbits as the rabbits run at slower speed compared to the foxes. Less number of rabbits are survived causing the rate of birth is lower to the rate of death of the rabbits. In the other hand, the rate of birth of the foxes is higher than the rate of death of the foxes. This is because of foxes consume on rabbits. Foxes run faster than the rabbits thus the average speed of the foxes is higher than the average speed of the rabbits. More rabbit die in this phase.

Then, for the next five years which is ten years, we can see that the graph increase rapidly. The average speed of the rabbits increase. This is because rabbits had evolved from slow runner to fast runner. As time flies, rabbits evolved to adapt with it surrounding environment. It has to run more faster to escape from the predator which is the foxes. In this phase, the average speed of rabbits highly increase. This natural selection pressure cause new rabbits born to evolved into faster rabbits. The rate of birth of the rabbits is higher than the rate of death of the rabbits. This is because, more faster rabbits can survive from being eaten by the foxes. While for the foxes, the rate of birth is lower than the rate of death. It is because, foxes that consume rabbits are unable to catch the faster rabbits as the rabbits now have been evolved. Thus, more fox die in this phase compared to the rabbits.

As time increase, the graph of average speed of the rabbits become flatter. The average speed of rabbits increase slowly. After the ten years, the newborn rabbits start to stop from evolved. This is due to less foxes prey on rabbits as the rabbits run more faster than the foxes. In this phase, the rate of birth of the rabbits is equal to the rate of death of the rabbits. In the other hand, the rate of birth of foxes also equal to the rate of death of foxes. As the rabbits start to stop evolved and the average speed of the rabbits increase slowly, foxes are able again to prey on slower rabbits. Foxes also may be undergo evolution to prey on faster rabbits. But in this experimant, the fox evolution thus not been take note because we only want to see the natural selection pressure on the rabbits. Thus, in this phase, less number of rabbits are die. However, there are also less number in newborn rabbits. Then we can say that the rate of birth of the rabbits is equal to the rate of death of the rabbits.

Then, by using the STELLA Software, some parameters are been added. The speed bias also be vary by decreasing it to 10.

Graph 2 : Graph of simulation with the bias speed set to 10.

Years	Average Speed Of Rabbits (ms)	Rabbits Being Munched	Rabbits Being Born
5	3	100	80
10	6	95	90
15	9	90	100
20	12	85	110
25	15	80	120
30	15	75	130

From the graph, we can see that some parameters had been added and the speed bias had been decrease to 10. The x-axis in the simulation is the years taken by the rabbits to evolve and at the y-axis is the parameters which is the average speed of the rabbits, the number of rabbits being munched and the number of rabbits being born. For the first five years, the average speed of the rabbits is constant. There are no increase in average speed of the rabbits yet as the rabbits still not evolved. The number of rabbits being munched is at higher number during this five years. The number of rabbits being born is at the lowest. This is because during this first five years rabbits do not evolve yet. The lower average speed of the rabbits causing it to be easy to catch by the foxes. Thus, in this phase, the rate of birth of the rabbits is lower compared to the rate of death rabbits. In the other hand, the rate of birth of the foxes is higher than the rate of death of the foxes. Foxes run faster than the rabbits thus the average speed of the foxes is higher than the average speed of the rabbits.

During the next five years, the rabbits start to evolved. However, because of the speed bias is changed into 10, the average speed of rabbits increase slowly or less compared to the Graph 1. The number of rabbits being munched had decrease and the number of rabbits being born increase. This is because of as the time flies, rabbits evolved to adapt with it surrounding environment. It has to run more faster to escape from the predator which is the foxes. In this phase, the average speed of rabbits increase slowly as the bias speed is lower than the normal. This natural selection pressure cause new rabbits born to evolved into faster rabbits. The rate of birth of the rabbits is higher than the rate of death of the rabbits. This is because, more faster rabbits can survive from being eaten by the foxes. While for the foxes, the rate of birth is lower than the rate of death.

As the year increase, the average speed of the rabbits increase slowly and become flatter. The number of rabbits being munched is decrease and the number of rabbits born exponentially increase. After the ten years, all the newborn rabbits had been evolved. This is due to less foxes prey on rabbits as the rabbits run more faster than the foxes. In this phase, the rate of birth of the rabbits is equal to the rate of death of the rabbits. In the other hand, the rate of birth of foxes also equal to the rate of death of foxes. Thus, as the natural selection pressure of the rabbits is decrease, the rabbits start to stop to evolved. This shows why the average speed of the rabbits start to be flatter as there are no more faster rabbits evolved. In this phase, the number of rabbits at its maximum number.

For the third graph, speed bias are change from normal to 30. The graph of average speed of rabbits, number of rabbits being munched and the number of rabbits being born are being studied.

Graph 3 : Graph of simulation with the bias speed set to 30.

Years	Average Speed Of Rabbits (ms)	Rabbits Being Munched	Rabbits Being Born
5	8	105	100
10	16	100	200
15	24	95	300
20	32	90	400
25	40	85	500
30	40	80	600

In the third graph, we can see the pattern of the graph is almost the same for all of the graph. However, the differences between all the graph is how steeper and flatter the graph due to difference speed bias that had been applied. For the last graph, we can see that for the first five years, the graph is constant. There are no increase in average speed of the rabbits. In this phase, rabbits not being evolved yet. The graph for rabbits being munched is the constant and highest while for the graph of rabbits being born is constant and at the lowest. Thus, the rate of birth of the rabbits is lower compared to the rate of death of rabbits. In the other hand, the rate of birth of the foxes is higher compared to the rate of death of the foxes. This is because at this phase, foxes prey on rabbits as the rabbits can not run faster. Foxes run faster than the rabbits make it easy to caught the rabbits. Thus, increase the number of death rabbits and lower the rate of birth of the rabbits.

For the next ten years, the average speed of rabbits is increase. The number of rabbits being munched is decreasing a lot or steeper. While the number of rabbits being born is increasing. At this phase, we believe that the rabbits have undergo evolution process due to the natural selection pressure. The rabbits had transform from slower rabbits into faster rabbits. This is due to the foxes prey on slower rabbits. Thus, the newborn rabbits is evolved into faster rabbits as it is adopt to its surrounding. The rabbits have to protect itself from the foxes since it is small. As the time flies, the rabbits evolved itself into the more faster rabbits. In this phase, foxes unable to caught the faster rabbits. Thus, the rate of birth of the foxes is lower compared to the rate of the death. The rate of birth of the rabbits is higher than the rate of death.

After ten years, the average of speed of the rabbits increase slowly. The average speed is still increase but not rapidly as ten years ago. This is because rabbits feel safe after being evolved so rapidly. Foxes can not caught the faster rabbits. However, foxes also can be evolved in order to get their food and maintain it population. The number of rabbits being munched is decrease and the number of rabbits born exponentially increase. After the ten years, all the newborn rabbits had been evolved. This is due to less foxes prey on rabbits as the rabbits run more faster than the foxes. In this phase, the rate of birth of the rabbits is equal to the rate of death of the rabbits. In the other hand, the rate of birth of foxes also equal to the rate of death of foxes. Thus, as the natural selection pressure of the rabbits is decrease, the rabbits start to stop to evolved.

5.0 Discussion

Natural selection is the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution. The term natural selection was popularized by Charles Darwin who intended it to be compared with artificial selection, what we now call selective breeding. Variation exists within all populations of organisms. This occurs partly because random mutations cause changes in the genome of an individual organism, and these mutations can be passed to offspring. Throughout the individuals lives, their genomes interact with their environments to cause variations in traits. Individuals with certain variants of the trait may survive and reproduce more than individuals with other variants. Therefore the population evolves.

Factors that affect reproductive success are also important, an issue that Charles Darwin developed in his ideas on sexual selection, for example. Natural selection acts on the phenotype, or the observable characteristics of an organism, but the genetic basis of any phenotype that gives a reproductive advantage will become more common in a population. Over time, this process can result in populations that specialize for particular ecological niches and may eventually result in the emergence of new species. In other words, natural selection is an important process by which evolution takes place within a population of organisms. As opposed to artificial selection, in which humans favour specific traits, in natural selection the environment acts as a sieve through which only certain variations can pass.

An experiment was conducted using STELLA Software to understand the relationship between the prey and predator of the rabbits and the foxes. This simulation also being used to observe the average speed of rabbits when different speed bias is applied. As the rabbits undergo natural selection pressure, the average speed of the rabbits will increase. There are some other parameters are being added to see the variation of the graph. The number of rabbits being munched will be decrease as the rabbits now be able to protect itself from the predator. The number of rabbits being born will be increase as the rabbits can grow until it is matured to breed more rabbits. Thus, when the rabbits being evolves, the rate of birth of the rabbits will be greater than the rate of death. Meanwhile, when the rabbits being evolves, the rate of birth of the foxes is lower than the rate of death.

Model structure of the life cycle of the rabbits.

6.0 References

http://en.wikipedia.org/wiki/Natural_selection (retrieved on 16/11/2012)

http://en.wikipedia.org/wiki/Simulation_software (retrieved on 16/11/2012)

http://en.wikipedia.org/wiki/Simulation (retrieved on 16/11/2012)

http://rationalwiki.org/wiki/Natural_selection (retrieved on 16/11/2012)

http://www.cise.ufl.edu/~fishwick/introsim/node1.html (retrieved on 16/11/2012)

http://www.iseesystems.com/aspx/WebLogin.aspx (retrieved on 16/11/2012)