Popsicle Stick Fish
Purpose: We are going to experiment with genes and environment for a
population of “popsicle stick fish”. We will look at genes, traits, variation,
survival and reproduction.
Materials:
1 “gene pool container” (a.k.a. bag)
8 green popsicle sticks
8 red popsicle sticks
8 yellow popsicle sticks
Introduction:
The colour of the popsicle stick represents a form of the gene (green, red
or yellow) that controls the colour of the fishes’ skin. The table below tells
you about the genes.
Green (G)
Red (R)
Yellow (Y)
Dominant over all other colours
Recessive to green
Co-dominant to yellow (yellow + red make orange)
Recessive to Green
Co-dominant to red (yellow + red make orange)
Remember it takes 2 genes to make a fish!
Methods:
1. Fill in the following table to help you determine the colour of the fish
created.
Genotype GG
GR
GY
RR
YY
RY
Colour
green
green
green
red
yellow
orange
2. Collect the materials and put all of the popsicle sticks in the bag.
3. Make a first generation of fish offspring by pulling out 2 popsicle
sticks and placing them aside as a pair. Repeat this process until you
have all 12 pairs.
4. Record the pairs in Table A using the proper codes for the alleles (see
table above). Write in the colours that result.
5. Count the number of each colour of fish offspring and record the
numbers in Table B. Add up the total number of offspring created
and record this in the table.
6. The stream where the fish live is very green and lush with algae &
plant life. The green fish are very well camouflaged from predators.
The red and orange fish hide fairly well. Unfortunately the yellow
fish stand out and tend to be eaten. If you have any yellow fish in the
first generation remove these popsicle sticks and set them aside.
Return the remaining popsicle sticks to the bag.
7. Draw a second generation of fish and repeat the entire process.
Remember to remove any yellow fish at the end, before returning the
sticks to the bag.
8. Repeat the process for the third and fourth generation. DO NOT
remove the yellow fish at the end of the fourth generation.
9. An environmental disaster strikes. Factory waste is dumped into the
water, killing the algae and some of the plant life. The remaining
rocks and sand are OK camouflage for the yellow, red and orange fish,
but now the green fish stand out. Remove any green fish at this time,
and record any surviving offspring in the last row of Table B.
Observations:
Table A: Gene Pairs and Resulting Fish Colours for 4 Generations
1st
generation
genotype
G Y
C C
G Y
C C
R R
C C
G Y
C C
CRCY
G Y
C C
G Y
1st
generation
phenotype
green
green
red
green
orange
green
green
C C
R R
red
C C
G Y
green
C C
Y Y
C C
R R
C C
G Y
C C
yellow
red
green
2st
generation
genotype
2st
generation
phenotype
3st
generation
genotype
3st
generation
phenotype
4st
generation
genotype
4st
generation
phenotype
Table B: Popsicle Fish Offspring Colour Numbers
Conditions
Generation Green
Red
Orange
st
Lots of green
1
7
3
1
nd
plants and algae
2
6
2
2
growing
3rd
6
3
1
everywhere
Plants and algae
4th
6
2
1
th
die off.
4
0
2
1
(survivors)
Yellow
1
1
0
Total
11
10
10
1
1
10
4
Conclusions:
1. Can 2 orange fish mate and have a red offspring? Why or why not?
2. After the 4th generation is pulled have all of the yellow genes
disappeared? Why or why not?
3. How and why has the population size changed before the
environmental disaster? Would you expect this to occur in the wild?
Why or why not?
4. How did the population size change after the plants and algae died
off? How did this compare to the changes in population after the
other generations? Explain why there is a difference.
5. Hatchery fish populations often have less genetic biodiversity (types
of genes available in the gene pool) than wild populations. How might
lower biodiversity affect a fish population’s ability to adapt to
environmental disasters such as the pollution disaster explained in this
simulation?
6. If the fish from a particular stream have become genetically adapted
to their home after many generations, what might happen if their
fertilized eggs are used to “restock” a different stream that has
become depleted of fish?