Initial Populations

The initial populations may have an effect on subsequent population sizes.

Observe the predictions of the model for values in these ranges:

Initial # rabbits (R) between 50 and 200
Initial # foxes (F) between 50 and 200
Rabbit birth rate (B) between .04 and .07
Fox death rate (D) between .04 and .07

Question 6: In the model, how does the initial size of the rabbit population affect the sizes of the rabbit and fox populations at later times?
The initial number of rabbits affects the fox population because as you can see the fox population starts to grow in the beginning however once the fox population starts to decrease the rabbit population increases drastically.

Also, the initial population of both the rabbits and the foxes starts out small. However by the end of the time period shown in the graph, they have grown exponentially as generations continue to reproduce.

Question 7: Does this prediction make sense? Why might the populations behave like the model suggests? Or why not?
This prediction makes sense, however the fox population could begin to find other animals for food. This would mean that the fox population would not depend upon rabbits all the time as a source of food and rabbit growth would not be kept in check by the fox population. This could lead to increases in both the rabbit and fox populations.

This prediction does make sense for these various reasons:

• when there is an abundant number of rabbits, there is going to also be an abundant number of foxes
• as the prey decreases, so will the predators

Question 8: In the model, how does the initial size of the fox population affect the sizes of the rabbit and fox populations at later times?
There is a very good correlation between the fox population and the rabbit population. The initial fox population is drastically higher than the rabbit population which will increase and decrease over time. By studying the graph it is easy to see that as the number of foxes decreases, the number of rabbits will increase at an accelerated rate. This pattern will continue to repeat itself over time.

Question 9: Does this prediction make sense? Why might the populations behave like the model suggests? Or why not?
This prediction makes sense because in the model, the foxes start out at 50 and the rabbits, 200. The rabbits exemplify the .07 birth rate, while the foxes exemplify the .05 death rate. This correlation between the 50-200 initial numbers and the birth/death rates of .04-.07, show a good representation of the graph explained.
The model predicts that with a lower initial number of animals, there will be less rapid increases in population when there is an increase. The model demonstrates a parabolic cycle between the two animals, having successive effects on each other. These populations behave like this model because:
* An increase in rabbit population causes
* An increase in fox population, due to nourishment
* An increase in fox population, decreases rabbit population
* Decrease in rabbit population, decreases fox population due to malnourishment
* Cycle starts over

NOTE: Until April 17, please answer only one of the unanswered research questions. If you have an original contribution to make on a question someone else already has answered, you may include it at any time.

page revision: 29, last edited: 24 Apr 2008 00:56