2. What is Biological Evolution?
Change over time
Descent with
modification
from a common
ancestor
University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu)
3. Descent with Modification
Genetic material is passed on from parent to
offspring.
The offspring is not identical to either parent.
Those differences determine how well adapted
the individual is to its environment.
Natural Selection
4. If the brown allele is dominant, what
will be the color of the offspring’s
Mohawk?
Mother (yy) Father (BB)
What color
will my
mohawk be?
5. If the brown allele is dominant, what
will be the color of the offspring’s
Mohawk?
Mother (yy) Father (BB)
What color
will my
mohawk be?
6. In this example the allele combinations
are not dominant or recessive. What will
be the color of the offspring’s mohawk?
What color
will my
mohawk be?
Mother (yy) Father (rr)
7. In this example the allele combinations
are not dominant or recessive. What will
be the color of the offspring’s mohawk?
What color
will my
mohawk be?
Mother (yy) Father (rr)
8. Fish Genotypes and Phenotypes
TABLE 1
ALLELE COMBINATION GENOTYPE
PHENOTYPE
(fish scale color)
Green (G) + Green (G) GG Green
Green (G) + Yellow (y) Gy Green
Green (G) + Red (r) Gr Green
Yellow (y) + Yellow (y) yy yellow
Red (r) + Red (r) rr red
Red (r) + Yellow (y) ry orange
9. What to Do:
• Follow the directions from your teacher to complete
Generation 1.
• Complete Table 2 as you go along.
• Use Table 3 to tally phenotypes from Table 2.
11. Generations 2-4
• Repeat the process for generations 2-4.
• Complete Table 2 as you go along.
• Use Table 3 to tally your phenotypes.
• At the end of each generation, remember to
remove all yellow fish (any fish with yy genotype)
• When you complete Generation 4 – DO NOT
REMOVE THE YELLOW FISH:
13. Environmental Change
• DO NOT remove any yellow fish.
• The environment has changed: now green fish
are easily spotted by predators and can’t survive
or reproduce.
• Remove any green fish (any fish with a green
phenotype/ with genotypes GG, Gr, or Gy).
• Count the remaining numbers of each phenotype
and record them on Table 3.
• Report your totals for the class chart.
14. Review Questions
How did the population size change over the generations?
Looking at Table 2, did any allele(s) disappear from the
population? What is more important to look at the phenotype
or genotype when determining if an allele has disappeared?
Why?
Was the population in Generation 4 Survivors different form
earlier generations? If so how was it different? Explain in
your own words why this occurred.
List the earth spheres that were important to the simulation,
and explain in your own words how they interacted?
Give an example of another change in an earth sphere could
affected the fish population?
15. The protein for brown eyes contains
melanin which will always mask the
protein for blue eyes.
brown eyes
(melanin)
blue eyes
Editor's Notes
If the young bug gets one recessive yellow allele from it’s mother (genotype yy) and one dominant brown allele from it’s father (genotype BB) what will be the color of the offspring’s mohawk?
If the young bug gets one recessive yellow allele from it’s mother (genotype yy) and one dominant brown allele from it’s father (genotype BB) the offspring will have the genotype By and have a brown Mohawk. The dominant brown allele produces a protein that has characteristics that are always dominant over the characteristics of the protein of the yellow allele.
In some allele combinations, there is not a clear dominant or recessive allele. This is called incomplete or co-dominance, and results in some expression of both alleles in the physical trait.
In some allele combinations, there is not a clear dominant or recessive allele. This is called incomplete or co-dominance, and results in some expression of both alleles in the physical trait. In this case, the combination the protein made from a yellow allele and the protein made from a red allele results in an orange Mohawk.
For a trait to be dominant, both alleles have to have a specific protein or there won’t be enough to express the specific trait. e.g. brown eyes are dominant because that gene’s protein produces melanin (brown coloring), so the eyes won’t be blue. If the eyes are blue, neither parent’s allele produces melanin. If a mother has blue eyes, the father has brown eyes, and they have a blue eyed child, the father must have one allele for blue eyes and one for brown eyes. The child received one blue eye allele from the mother and one from the father. Two blue eye alleles means the child will have blue eyes.
There are 3 possible alleles:
Green - dominant
Red - recessive
Yellow - recessive
What are all the possible combinations of alleles?
GG
Gy
Gr
yy
rr
ry
A healthy pond environment containing fish of four different colors. What do you notice about the fish?
1.
The environment has changed in the pond due to chemicals leaking into the water and causing a change in the color of the green pond plants. What do you now notice about the colors of the fish in the changed environment?
The green fish will now be more easily seen by predators and will most likely become less numerous in the fish population than the yellow, red, and orange fish which are more easily camouflaged. Although the red and yellow alleles are always recessive to the green allele, with less green alleles in the overall population to be expressed, the red and yellow alleles will be expressed more often and there will be more red, yellow, and orange fish in the population.
1. Did all the yellow alleles disappear by Generation 4? The yellow allele has at least decreased in number for most, if not all, groups. Few groups may no longer have yellow alleles though it is unlikely.
2. How did the population size change? As yellow fish die, the population size decreases. After the disaster, population shows a steep decline.
3. How was the population for Generation 4 Survivors different from earlier generations? Much smaller since we removed the dominant allele.
4. Have any alleles disappeared completely? Some groups may no longer have yellow alleles.
5. Which color of alleles decreased faster in Parts Two and Three? Yellow decreased slowly in Parts Two and Three. Only yellow fish (two yellow alleles) were removed so the allele survived in fish that had a green allele (dominant) or red allele (incomplete dominance).
7. Which alleles disappeared fastest in Part Four? In Part Four, all green alleles were wiped out.
8. What do you predict will happen to this fish population as these fish reproduce? The numbers of red, orange, and yellow fish will increase as these fish reproduce.
9. Will green fish ever return to this pond? Only if a green fish is introduced from another area. Otherwise, only red, orange, and yellow fish will exist in this habitat.
Brown eyes are always dominant because the protein for brown eyes contains melanin which is always dominant over the protein for blue eyes. The characteristic of melanin always masks the blue eye color. These protein characteristics are what makes an allele dominant or recessive.
