Explorations
This file gives some play suggestions for the Scenarios included in the Gecko GrassWorld demo.
For what it all means, please see the
Discussion instead. The
Help reader explains how to operate
the gizmos on the screen. Further readings are listed in References.
Scenario: Unstable Quickie
This is the scenario automatically launched when Gecko is loaded,
and shown in the sphere pictures in the Discussion. If you try it a few times
(click Restart), you'll find the spiders eat off all the
grasshoppers very quickly.
- Use one spider instead of two:
- Click Parameters
- Select Spider
- Change "initNumber" to 2 and click "OK"
- Click on Restart
How much longer do the grasshoppers last? If any
are still alive by the stop time, you can click on
Continue, and optionally change the stop time
via RunControl.
-
A theory: if there are no spiders to control the
grasshoppers, the grasshoppers will kill off all the
plants and then die of starvation. True?
-
Another theory: with no grasshoppers and no spiders,
and the faster reproductive advantage of Plant over
BigPlant, [...your theory here...] Try it. [Hint: look
at biomass over the long haul. You can speed things up
for the long haul by setting the display cycle to 20.]
- Would a bigger reproductive advantage for Plant
help? How about a breedsize on Plant of 5 and on BigPlant
of 10? If you added a grasshopper at time 1000, would
either plant species benefit?
- If BigPlant's breeding radius is set high enough,
it can keep growing even past its breeding radius. This is
because it only spawns one child per timestep, and if it's
big enough, it can get more resources than needed for a
seed.
- There are other funky parameters here. Click on
Scenarios | Unstable Quickie again to get back
to the original settings, and try some of them.
- Gopper veer is fun. It's expressed in radians,
so the default of 3.77 = 216 degrees. Try .785, or about 45 degrees.
-
Spider smell radius is fun, though this scenario might be
too small to grow it. Try setting it down instead. Note that
smell radius is a multiplier on the spider's current
size, not an absolute radius. If it were absolute, the default
settings would mean the spider couldn't smell as far as he
could eat.
Scenario: 2 Plants + Gopper + Spider
-
The last scenario had 2 Plants + Gopper + Spider.
What's different?
Scenario: Plant/Gopper/Spider (orig basic3)
This is the original Gecko test case, with us since Gecko's
prototype in 1994. The goal is to have a stable 3 trophic level
model exhibit a "trophic cascade". That means that plant
biomass should be highest with no grazers present. With grazers
but no grazer predators, plant biomass should be lower. With
grazers and their predators, plant biomass should be
intermediate between the two other levels.
This scenario is bigger and slower than the other two. If you
make it much smaller, though, it may not stay stable (all 3
species persist) very well.
- Want to demonstrate the trophic cascade to yourself? (Kinda
tedious.)
- To turn on further statistics, click RunControl. Try
looking at Plant | Biomass Theft. This plot shows the amount of
Plant biomass eaten by goppers (y-axis) vs. standing Plant biomass
(x-axis.) Leave it on
through a few boom/bust cycles.
- Change Gopper veer to 6.28, that being roughly 360 degrees.
How do the dynamics change?
Ginger Booth, September 17, 1999