MIHS-20_Period4_NickN_LeanderS_MillaL_CaitlinR

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3 collaborators

Nicholas Novack (Author)

milla rose (Advisor)

Leander Schatz (Advisor)

WHAT IS IT?

This model is meant to represent the populations of two different species competing in the same ecological Niche.

CHANGES

We added a second breed, cows, that compete with sheep for grass.

HOW IT WORKS

This model uses turtls to represent the two different species and patches to represent their shared food surce, grass.

HOW TO USE IT

Adjust the sliders to change the variables such as grass growth, initial population size, and movement cost.

THINGS TO NOTICE

The graph at the bottom left shows the populations of the two differnt species.

THINGS TO TRY

Adjust the starting populations to be different, and watch how it affects which species survives.

EXTENDING THE MODEL

Predators could be added to better repreent the ecosystem.

RELATED MODELS

This model is very closely related to the Wolf Sheep models.

CREDITS AND REFERENCES

This model is a modified version of the Wolf Sheep Simple 4 model.

Comments and Questions

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Click to Run Model

breed [sheep a-sheep]
breed [cows cow]
turtles-own [ energy ]  ;; agents own energy

patches-own [ grass-amount ]  ;; patches have grass

;; this procedures sets up the model

to setup
  clear-all
  ask patches [
    ;; give grass to the patches, color it shades of green
    set grass-amount random-float 10.0
    recolor-grass ;; change the world green
  ]
  create-sheep number-of-sheep [
    setxy random-xcor random-ycor
    set color white
    set shape "sheep"
    set energy 100
  ]
    create-cows number-of-cows [
    setxy random-xcor random-ycor
    set color brown
    set shape "cow"
    set energy 100
  ]
  reset-ticks
end 

;; make the model run

to go
  if not any? turtles [
    stop
  ]
  ask turtles [
    wiggle        ;; first turn a little bit
    move          ;; then step forward
    check-if-dead ;; check to see if agent should die
    eat           ;; sheep eat grass
    reproduce     ;; the sheep reproduce
  ]
  regrow-grass    ;; the grass grows back
  tick
  my-update-plots ;; plot the population counts
end 

;; check to see if this sheep has enough energy to reproduce

to reproduce
  if energy > 200 [
    set energy energy - 100  ;; reproduction transfers energy
    hatch 1 [ set energy 100 ] ;; to the new agent
  ]
end 

;; recolor the grass to indicate how much has been eaten

to recolor-grass
  set pcolor scale-color green grass-amount 0 20
end 

;; regrow the grass

to regrow-grass
  ask patches [
    set grass-amount grass-amount + grass-regrowth-rate
    if grass-amount > 10.0 [
      set grass-amount 10.0
    ]
    recolor-grass
  ]
end 

;; sheep procedure, sheep eat grass

to eat
  ;; check to make sure there is grass here
  if ( grass-amount >= energy-gain-from-grass ) [
    ;; increment the sheep's energy
    set energy energy + energy-gain-from-grass
    ;; decrement the grass
    set grass-amount grass-amount - energy-gain-from-grass
    recolor-grass
  ]
end 

;; asks those sheep with no energy to die

to check-if-dead
  if energy < 0  [
    die
  ]
end 

;; update the plots in the interface tab

to my-update-plots
  plot count sheep
  plot count cows
end 

;; sheep procedure, the sheep changes its heading

to wiggle
  ;; turn right then left, so the average is straight ahead
  rt random 90
  lt random 90
end 

;; sheep procedure, the sheep moves which costs it energy

to move
  forward 1
  set energy energy - movement-cost ;; reduce the energy by the cost of movement
end 


; Copyright 2007 Uri Wilensky.
; See Info tab for full copyright and license.

There is only one version of this model, created over 4 years ago by Nicholas Novack.

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