EVOLUTION SCORING RUBRIC – Essay Question

EVOLUTION SCORING RUBRIC – Essay Question
I would use this scoring rubric for an essay question on the topic of evolution. It may be helpful for
you as a student (and future teacher) to take a look at the rubric AND the content information it
contains.
FYI: Student answers to the following evolution question were used in rubric development:
Cheetahs (large African cats) are able to run faster than 60 miles per hour when chasing prey.
How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their
ancestors could only run 20 miles per hour?
Example #1
Student’s answer: The cheetahs adapted to their environment.
Scoring:
Darwinian Component #1: 0
Darwinian Component #2: 0
Darwinian Component #3: 0
Darwinian Component #4: 0
Scoring note: A score of 1 indicates that a word or phrase was
identified for this category; whereas a 0 indicates that no
phrases or words were identified that met the requirements
of the category.
Adaptation is too complex a process to award any points for this simple answer. It is responses like this
one that cause teachers to write, for example, “Responses must contain more than 15 words.” There are
times when simple answers are appropriate, but this answer fails to provide evidence about this
student’s understanding of biological evolution.
Example #2
Student’s answer: The cheetahs mutated and became faster. They mutated until they could run 60 mph.
Scoring:
Darwinian Component #1: 1 (mutated)
Darwinian Component #2: 0
Darwinian Component #3: 0
Darwinian Component #4: 0
This response contains one idea that is consistent with Darwinian evolution, that being the notion of a
mutation. But this scoring is generous in that other issues are not included in the student’s answer.
Many students know that the word “mutate” is key to evolution, indeed “mutation” is identified for
Darwinian Component #1 in the rubric. The above answer shows that the student knows that mutations
could lead to increased speed. However, by stating that “the cheetahs mutated,” it seems that the
student thinks that all the cheetahs mutated at the same time, and thus does not understand variation
within the population of cheetahs. This is inconsistent with Darwinian Component #1, and is a
misconception about the frequency of mutations within populations.
Example #3
Student’s answer: Some of the cheetahs mutated and the faster ones were better able to catch prey.
They evolved until now they can run 60 mph.
Scoring:
Darwinian Component #1: 1 (Some of the cheetahs mutated.)
Darwinian Component #2: 0
Darwinian Component #3: 1 (The faster ones were better able to catch prey.)
Darwinian Component #4: 0
This student implies variation within the population by stating that “Some of the cheetahs mutated” and
also states that the faster cheetahs had an advantage over the slower cheetahs (i.e. “Faster ones were
better able to catch prey”). The phrase “They evolved until now they can run 60 mph” does not contain
any mechanism for evolution and is not coded. (Note: Some instructors would not agree that this
answer meets the criteria for Darwinian Component #1 because technically cheetahs can’t mutate, but
rather a cheetah’s genes mutate. The level of precision required within students’ answers is highly
variable between instructors.)
Example #4
Student’s answer: Some of the cheetahs were able to run faster than other cheetahs. The faster ones had
kids that were faster than the others.
Scoring:
Darwinian Component #1: 1 (Some … were … faster … than others.)
Darwinian Component #2: 1 (The faster ones had kids that were faster.)
Darwinian Component #3: 0
Darwinian Component #4: 0
Without going into the depths of genetics, this response indicates that something (speed, in this case) is
being passed from one generation to the next. The text in this response is probably the minimal content
required to fulfill the Darwinian Component #2 category.
Example #5
Student’s answer: Some were fast and others were slow. The fast ones had an advantage in that they
were able to catch more food. The slower ones starved. The fast ones evolved to 60 mph.
Scoring:
Darwinian Component #1: 1 (Some were fast and others were slow.)
Darwinian Component #2: 0
Darwinian Component #3: 1 (The fast ones had an advantage … . The slower ones starved.)
Darwinian Component #4: 0
This student recognized that there was variation within the population, and also the advantages and
disadvantages that this variation created, which is a component of the Darwin Component #3 category.
Example #6
Student’s answer: The faster ones were able to catch more food, and the slower ones had a more
difficult time catching food. The faster ones reproduced and had kids that were also fast, and they had
an advantage over the kids from the slower ones.
Scoring:
Darwinian Component #1: 1 (The faster ones … the slower ones.)
Darwinian Component #2: 1 (The faster ones reproduced and had kids that were also fast.)
Darwinian Component #3: 1 (The faster ones were able to catch more food, and the slower ones had a
more difficult time catching food.)
Darwinian Component #4: 0
This student recognized that there is variation within the population, that the trait of being fast was
passed to the next generation, and that there was an advantage to being fast. The word “advantage” is a
minimal response for Darwinian Component #3 in that the student does not indicate what that
advantage ultimately means (i.e. differential survival and reproduction).
Example #7
Student’s answer: There was a mutation in the 20-mile-per-hour cheetahs that allowed some to run
faster than the others. The mutated cheetahs were able to catch more food. Their kids inherited the
mutation and had an advantage over the kids who did not have the mutation. The ones without the
mutation became extinct, but the ones with the mutation lived on until now they can run 60 miles per
hour.
Scoring:
Darwinian Component #1: 1 (mutation, some run faster than others)
Darwinian Component #2: 1 (Their kids inherited the mutation.)
Darwinian Component #3: 1 (had an advantage, the ones without the mutation became extinct.)
Darwinian Component #4: 1 (The ones with the mutation lived on until now they can run 60 miles per
hour.)
This response did not use the term “adaptation” and misused the term “extinction,” but it implies that
over time the percentage of faster cheetahs increased. Many teachers would not agree that this student
shows an understanding of the concept of adaptation (Darwinian Component #4), but the text can be
interpreted to show at least a minimal comprehension. Additionally, the phrase “There was a mutation
in the 20-mile-per-hour cheetahs” could be interpreted to mean that adult cheetahs mutated which
would be problematic in terms of how that mutated trait would be passed to the next generation.
Example #8
Student’s answer: A long time ago cheetahs could only run 20 miles per hour, but a few of them could
run a little faster because of a mutation or something. Those that could run faster had an advantage
over the others because they could get more food and stuff. The faster ones gave their kids the mutation
and they could run faster than the others. The slow ones died and the fast ones lived and had kids. Some
of those kids mutated again and became even faster. This happens over and over again until now most
all cheetahs can run 60 miles per hour.
Scoring:
Darwinian Component #1: 1 (… but a few of them could run a little faster because of a mutation)
Darwinian Component #2: 1 (The faster ones gave their kids the mutation.)
Darwinian Component #3: 1 (Those that could run faster had an advantage.)
Darwinian Component #4: 1 (This happens over and over again until now most all cheetahs can run 60
miles per hour.
This student’s response better explains adaptation than Example #6, and also does a good job of
covering the other Darwinian categories. However, it would be very interesting to have the student
explain how the parent cheetahs “gave” the mutation to their kids, and also how the “mutation or
something” initially occurred. Could they elaborate a bit more on the “or something”?
Figure 1. Scoring Rubric Used
Darwinian Component #1: Variation
KEY TERMS & CONCEPTS
variation within a population
There exists within every population
genetic differences
variation between individuals and the origin
mutation in the genes/DNA
of that variation is chance.
mutation as a source of variation
change due to a mutation
There was a mutation.
There was a change in the genes/DNA.
Darwinian Component #2: Genetics
KEY TERMS & CONCEPTS
passed on to the next generation
Organisms pass inheritable information from
Something in the genes is passed to the next
one generation to the next.
generation.
Genes were passed on.
passed to their offspring
passing on genes
The dead one’s genes were not passed on.
Darwinian Component #3: Differential
KEY TERMS & CONCEPTS
Survival & Reproduction
Limit in resources
some survived, many died/survival of the fittest
There occur in nature events where some
potential fertility/geometric reproductive rate
organisms die and others survive. However,
The total population size usually remains about
over time, population size remains relatively
the same.
stable.
struggle for existence
fitness: the number of offspring produced
death/many died/some died/all died
some survived
enabled them to survive/live/eat/reproduce
The food was limited (limits in natural
resources).
extinction
Darwinian Component #4: Change Over
KEY TERMS & CONCEPTS
Time
There were more of them than in the previous
generation.
Over time, the percentage of a population
more and more individuals with the trait/genes
that possesses a specific trait increases in
changes in the percentage of individuals within
frequency. This is the concept of adaptation.
the population with specific traits or genes
(sometimes students use the word
“dominant” to denote this concept which is a
common genetic/evolution misconception)
changes to a population over time
changes in the percentage of individuals with
specific traits
population genetics