Learning from the Fossil Record
Grade 8 Science
Name:
Date:
Part1 of Performance Assessment Task
In analyzing the fossils in each layer, the scientists were able to identify some key features that
struck them as interesting. Unfortunately, the digital camera they used to take pictures was
damaged and they are unable to send you pictures at this time. They would like, however, you
to begin determining the possible inheritance of traits seen. They were able to send you the
following descriptions.
Deepest fossil layer: all
short skull and jaw
Long, skinny tail
Long front legs
Long back legs
No flukes on the tail
Next fossil layer:
some
short skull and jaw
Long, skinny tail
Long front legs
Long back legs
No flukes on the tail
Next fossil layer:
all
Long skull and jaw
Short, fat tail
Front flippers
Short back legs
Flukes on the tail
Next fossil layer:
all
Long skull and jaw
Short, fat tail
Front flippers
No back legs
Flukes on tail
some
long skull and jaw
short, fat tail
short front legs
long back legs
no flukes on the tail
By studying present day animals with similar traits, they have inferred that:
1. Long skull and jaw are dominant over short skull and jaw
2. Short thick tail are dominant over long skinny tail
3. Long front legs is dominant over short front legs
4. Long back legs is dominant over short back legs
5. No flukes on tail is dominant over flukes on tail
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
They ask that you send a report of your findings on the possible genetics and inheritance of
these traits. They do know all of these fossils are related as the area was isolated and no other
animals could come in or go out of the area.
Please include the following in your report.
1. How is it possible for the recessive short skull and jaw trait to change to a dominant
long skull and jaw trait and stay that way permanently?
2. How is it possible for the recessive long, skinny tail trait to change to dominant short,
thick tail trait and stay that way permanently?
3. How is it possible for the dominant long front legs trait change to a recessive short front legs
trait and then turn into flippers?
4. How is it possible for the dominant long back legs trait to change to a recessive short bag legs
trait and then disappear completely?
5. How is it possible for the dominant no flukes on tail trait to change to a recessive flukes on tail
trait and stay that way permanently?
Red text indicates the example that will be used by the teacher to model the process.
Each answer will be scored on the following aspects:
a. Does the reasoning behind the answer make sense and is it possible? 0 1 2 3
b. Is the reasoning behind the answer supported by data (e.g., Punnett Squares, diagrams,
explanations)? 0 1 2 3
c. Where reasoning cannot be found using genetics, is a reasonable prediction made? 0 1 2 3
d. Is the report organized in a logical manner so the reader can understand the explanations
provided? 0 1 2 3
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
1. -In the first fossil layer, all of the organisms had long and skinny tails. This was because all of
the organisms had the ss genotype, homozygous recessive.
-In the next fossil layer, both the long and skinny tails AND the short and thick tails came into
existence. This means that both the ss and Ss/SS genotypes were present. The ss genotype
was present because the creatures mated and had children with ss genotypes, which should
be the only possible combination. Outside of genetics, the genes changed and somehow the
animals ended up with the short and fat tail genes. It could have been possible that the short
tail had developed through the environment and the genes changed in response.
-In the next fossil layer, the animals all had short, thick tails. This means that only the SS/Ss
genotypes existed anymore. This could have been caused by the long skinny tails causing
death to the animals, so all the animals having it died. Possibly it was dragging through the
dirt and making more tracks that could be followed by predators.
-In the final layer, all of the animals again had short, thick. While this means that, yet again,
the only genotypes were SS/Ss, it almost completely rules out the possibility of an Ss
genotype existing. If it had been still around in the previous fossil layer, at least some of the
animals in this layer would have been homozygous recessive (ss) and had the long, thin tails. It
would just be too unlikely. This means that all the animals would be SS.
2. –In the first fossil layer, all of the organisms have long front legs. Since long front legs are
dominant over short front legs, the genotypes are all either LL or Ll.
-In the next fossil layer, the organisms have both long AND short front legs. As short front legs
is the recessive trait, it is possible if two heterozygous long legged creatures mated and had a
short legged child, having given said child both their recessive genes. So up to this point all
three genotypes (LL, Ll, and ll) are all probably present.
-In the next fossil layer, all of the creatures end up developing flippers in place of front legs.
These flippers are not genetically accounted for as a possible allele, so they could either be the
part of a gene mutation or a need for flippers, such as a rising water level or too much
competition for food on land.
-In the last fossil layer, the creatures all also have front flippers. This essentially owes itself to
the fact that the genes themselves have changed in the animal, or else the generation would
be born again with legs. The population of animals probably has been flooded with water and
is now a water animal. The changes are now permanent, and whether or not flippers are
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
dominant or not does not matter, as it seems there would be no alternative as a water
creature.
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