PsL Monthly 1994 January

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Bugs Alive Bugs Alive is an evolution simulation program. It has the challenge of a game while at the same time it teaches about the processes that drive natural selection. It challenges the user of the program to set up an environment and then to explain how and why things change. (Program requires EGA color graphics.) The program consists of plants, bugs, and predators. PLANTS The plants are almost round structures that are green in the summer and turn gray in the winter1. They can only grow in certain areas of the screen. The number of fertile areas for plant growth can be controlled by using the Density statement in a control file. The Pattern statement can also be used to create a specific pattern of fertile areas on the screen. It will override the density statement. The Growth statement controls the rate of plant growth in the summer and death in the winter. BUGS The bugs are little colored squares that swarm around the screen eating the plants, growing, and reproducing. There are three sizes and six colors that indicate the energy of each bug. The larger the size the higher the energy level. When a bug has acquired sufficient energy from eating green plants and if it is summer the bug will split (asexual reproduction). At this point of reproduction several factors can change; i.e. o Visual Range Farthest distance can see plants o Energy Use Efficiency of plant use for energy o Death Run Point Energy level for start of Death Run o Hibernate Presence or absence of Hibernate factor These factors will either increase, decrease or remain unchanged. The change or mutation rate at this point is very high, several orders of magnitude higher than a real situation. However, who wants to run a program for several months or years in order to notice change. Bugs can only see food in the direction in which they are moving and are limited to a fixed visual range. This visual range can change at the time of reproduction. The value listed in the report is the average for the population. When a bug's energy level drops below a certain point, the bug will pick a random direction and move in that direction until it either finds green plants or dies. This is the Death Run. The average point at which the Death Run for the population starts is given in the report file. The Bug population starts out with about five percent of the bugs having a hibernation factor. This factor also has a five percent mutation rate at reproduction. If a Bug has this factor and their energy efficiency level is below a given point2 then they hibernate during the winter to save energy. A hibernating Bug will appear to freeze on the screen. The environment wraps around on the screen; left to right and top to bottom. The bugs do not notice this and are able to pass and see across these transitions. The Number command in the command file can be used to establish an initial number of bugs this can be anywhere from 1 to 500. However, the greater the number of Bugs and predators the slower the program will run. When the last Bug has died the program will terminate.3 If a large number of bugs are produced they will begin to feel population stress and die a natural death at a faster rate. Predators Predators appear on the screen as small circles. While they have only one size they do change color as their energy levels change. Predators remain stationary unless they are chasing a Bug. This is because they use a much higher level of energy when moving. Predators also have several factors that can change when reproduction occurs (also asexual). These factors are; o Visual Range Distance can see Bugs o Speed Speed of movement o Energy Use Efficiency use Bugs for energy The visual range for the predators is the base visual range at which they can see the smallest Bug. Larger bugs can be seen at slightly greater distances depending on size. It is only the base visual range that can change during reproduction. The speed which a Predator moves after a Bug is also subject to change at the time of reproduction. The slowest that a Predator will move is the same as the Bugs. However, with selection and change they can move up to five times faster. Energy use for Predators is almost the same as for Bugs except that Predators eat Bugs. This means that energy use indicates how much energy a Predator can get from a bug, above the basic level. Unless a Zero Predator option is chosen in the Predator statement in the control file a new predator will periodically wander into the environment. The default rate is once in ten years, however, this can be changed with the Addpredator statement in the control file. While Predators can travel across the boundaries at the edges of the screen because they can not see across these boundaries they rarely cross them. Control File There is only one command line option when starting the program. The name of a control file. This file when present contains a series of statements that can adjust some of the variable aspects of the Bug's environment. Each command in the control file is case insensitive i.e. the letters can be any mixture of upper and lower case. There is also no defined order to their appearance or requirement that they appear. A control file could contain as few as a single statement. Below is a control file and description of each statement. The descriptions should not be included within the control file. number 30 Number of starting bugs (1-500); growth 10 Rate of plant growth (1-100); plant 150 Number of initial plants (1-1000); density 25 Number of fertile land locations (1-50); summer 3 Length of summer, 100 pixel moves (1-100); predators 3 Starting predator number (0-50); addpredator 15 Add predator on average every # years (1+); linked negative Link change in visual range and energy use (positive, negative) pattern 1 OOOOXXXXOOOO Create pattern of plant growth by row pattern 2 OOOXXOOXXOOO number. X's are locations for plants. This pattern 3 OOXXOOOOXXOO statement overrides density; pattern 4 OXXOOXXOOXXO pattern 5 XXOOXXXXOOXX pattern 6 XXOOOOOOOOXX Number 30 The number statement can be used to establish the initial number of bugs when the program starts. The statement above would start the program with thirty bugs. If this statement is not included or a control file is not used then a default number of bugs somewhere between 5 and 20 will be produced. The number of starting bugs that this statement will accept must fall somewhere between 1 and 500. Exceeding this range will result in five Bugs as a starting value. Growth 10 The growth statement is used to control the rate of plant growth in the summer and plant death in the winter. It uses an ordinal number falling between 1 and 100. The higher this number the greater the rate of plant growth and death. Plant 150 Plant is a statement that controls the initial number of plants on the screen when the first summer starts. It uses an ordinal number falling between 1 and 1000. The higher this number the more plants present at summer. Density 25 The density statement controls the number of locations of fertile land where plants can grow. These locations will be randomly distributed throughout the screen. The range of values can fall between one and fifty. If a pattern statement is used this statement need not be included as it will be overridden. Summer 3 Summer is a statement that controls the length of summer and winter. The seasons are measured in one hundred bug moves. A three as given above would indicate that summer will last three hundred bug moves. Winter is always one third the length of summer. The range of possible choices is one to one hundred. While the seasons are progressing a bar will grow4 in the bottom line of the screen so that you may judge the relative time within the season. Predators 3 The predators statement can be used to establish an initial number of predators. If it is not included or a control file is not used then one predator for each ten bugs will be used at the start of the program. The statement given above will cause three predators to be present when the game starts. If the value in the predators statement is set to zero then there will not be any predators at the start of the program and none will periodically wander into the environment. However, Predators can still be introduced through the special keys listed below. The range of initial predators can fall between zero and fifty. Addpredator 15 This statement can be used to determine how many years, on average, will divide the times when a predator periodically wanders into the environment. It should be remembered that this is a random process therefore it is possible for a predator to appear on two successive years when the interval is set to something like every fifteen years as it is above. The range of values can be any whole number greater than zero. Linked negative The linked statement will allow the user to explore the effects of linking two factors at the time of change (reproduction). These factors are visual range and energy use. The two options for this statement are positive and negative. The result of linkage means that at the time of reproduction when change can take place, the nature of the change in one factor will be related to the change in the other. When they are positively linked an increase in visual range will be associated with an increase in energy usage or a decrease in one would also mean a decrease in the other. For negative linkage if one factor increases the other will decrease. If this statement is not used or a control file is not used then these two factors will not be linked. They can then change independently of each other. Pattern 1 OOOOXXXXOOOO The pattern statement is used to establish a pattern of positions of fertile land for plant growth. The second value in the statement is the row number starting with the top of the screen. There are a total of six possible rows. The third field is a string twelve positions in length. Each position represents one of twelve columns across the screen. Where the X's are located, that column and row will have fertile land. The other positions in the string can be filled with any character. The pattern statements need not be in row order, however, it is easier to visualize if they are. When this statement is used the density statement will be overridden. Special Keys There are two groups of special keys. The first is a single key that allows you to exit the program prior to the death of the final bug (handy when a equilibrium state is established). This is done by pressing the 'Q' key. The others are the ten number keys on the key pad or the top of the keyboard. When using the keypad they must be used as number keys not direction keys. Pressing one of these keys when the program is in operation will introduce a predator at a random location within the corresponding area of the screen; i.e. 7 is upper left, 5 is center, and 3 lower right. The zero key will place a predator in some random location on the entire screen. Report File After the program ends you will find a report file 'BALIVE.REP' on your disk. This is a summary of births, deaths and the status of the changeable factors for bugs and predators for each year. This is the data that you may use to test various scenarios that you establish through the control file. The next time the program is run this file will be overwritten by a new file so change its name if you want to save it. Please send a shareware contribution of $10 to Acinom Software 7301 Lanham Lane Edina, MN 55439 1 There are only two seasons; Summer and Winter. 2 I will let you try and figure out this point. 3 The other way to terminate the program is to press the Q key. 4 Summer's bar is green and winter's bar is gray. ----------------end-of-author's-documentation--------------- Software Library Information: This disk copy provided as a service of Public (software) Library We are not the authors of this program, nor are we associated with the author in any way other than as a distributor of the program in accordance with the author's terms of distribution. Please direct shareware payments and specific questions about this program to the author of the program, whose name appears elsewhere in this documentation. If you have trouble getting in touch with the author, we will do whatever we can to help you with your questions. All programs have been tested and do run. 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