CS108L Spring 2014
Week 13: DO NOW QUESTIONS
1. Suppose you had a working model of small fish feeding and living in the
ocean. How could you change the code below to make the model more
general so that you could explore a variable without having to change the
actual code each time?
a. Change the name of the procedure to BigFishWiggle
b. Change line iv “Forward 2”
c. ***Add a new slider called newSlider and change line v “set Fenergy
Fenergy – newSlider”
d. Include a line that “Ask fishes [ set size 3 ]”
Answer: c. It is very valuable useful to have students add sliders so that they
can explore how changes to the model affect the model behavior. Any fixed value
in the code may be a candidate for replacing with a slider. Make sure that the
slider interval and increment make sense in the given context.
2. “Breeds” allow programmers to have different kinds of turtles with different
custom variables for each breed. The names also help programmers keep
track of which agentset they are working with. What does the following
command do?
a. Immediately Creates 100 sharks
b. Allows you to use the command “create-sharks” later in your code
c. Allows to use a command like sharks-own [hungry?] later in your
code.
d. ***b and c above.
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Answer: d. Breeds can be confusing to new programmers. They are mostly just
a way to make your code easier to read, understand and program. They become
especially useful when you have agents in your model that have different
behaviors and require different custom variables or [breeds–own] variables.
Students should use breeds whenever possible because it make the models more
descriptive and helps them connect with the underlying phenomena that they
are modeling. Creating a breed allows you to use several NetLogo commands
that are breed specific—for example, the create-sharks command, the sharksown command, and the ask sharks [] block.
3. In a model that has fish that are moving and expending energy; eating and
gaining energy; why might you want to have the code below?
a. To punish the fish for not doing what you say.
b. To model the consequences of running out of food.
c. To make a more accurate model of sustainability—fish die when
resources are depleted.
d. ***b and c
Answers: d. Understanding the real world rationale for each part of a model is
important. It is what modeling is really about. It is easy to lose sight of this when
student are struggling with just learning how to program. It is more realistic for
a model of a fish eco system to include fish running out of resources and dying.
4. The concept of “carrying capacity” is important in biology. It means that a
given environment only has enough food (or space, etc.) to support a certain
number of organisms. In a model that has fish moving (spending energy),
eating (gaining energy), and reproducing when they have gained enough
energy. What limits the fish population?
a.
b.
c.
d.
The amount of food available
The number of other fish
The amount of energy that they need to reproduce.
***All of the above
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Answer: d. all of the above. Again, this Do Now question focuses on
identifying the variables that contribute to determining the fish population at
any point in time. This is a good opportunity to point out that many real world
situations are the result of the interplay between many factors. Figuring out
what those factors are and how much (or how little) they impact the situation is
why we need models.
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The amount of food is a factor because it is the source of the energy that
fish need to reproduce.
The number of other fish impacts the competition for resources. A big
part of our environment is our relationship with others of our own kind.
The threshold of energy necessary to reproduction is also important.
How much energy is gained from food.
In the lab, consider having students identify ways to manipulate each of these
variables in the code.
5. You have created a simple fish ecosystem model with fish and plankton. Not
you want to add a predator, say a shark. What things do you need to
include?
a.
b.
c.
d.
A new breed perhaps called shark
An interaction between the shark and the fish
Procedures that allow the shark to move around, give birth and die.
Nothing, you just need to put the shark into the model and let nature take
its course
e. a, b and c
Answer e. a, b and c This do now focuses on adding a predator to an existing
model. In order to do that you must create the breed, have it interact with the
prey and do the things that cause it to move around and breed.
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