Natural Selection Assessment
Post Assessment Questions:
1) Antibiotics are given to cows and chickens to kill bacteria that live in the animals’
digestive systems and make the animals grow faster. But scientists have found that
giving antibiotics to farm animals leads to populations of antibiotic-resistant bacteria
that are dangerous to humans. How can the population of bacteria in a cow’s digestive
system become more resistant to antibiotics?
2) Suppose that long ago there was a population in Northern Michigan with three kinds
of hares (rabbits):
 Hares that were white ALL the time
 Hares that were brown ALL the time
 Hares that were white in the winter and brown in the summer
Explain how natural selection and reproduction would change the population over time.
3) It is thought that the ancestors of cheetahs could only run 20 mph. Now cheetahs
have been seen running 60 mph. How would a scientist explain how cheetahs gained
the ability to run raster?
Final Assessment Questions w/ Answers:
Excellent Response or Rubric
1) Antibiotics are given to cows and chickens to kill bacteria that live in the animals’
digestive systems and make the animals grow faster. But scientists have found that
giving antibiotics to farm animals leads to populations of antibiotic-resistant bacteria
that are dangerous to humans. How can the population of bacteria in a cow’s
digestive system become more resistant to antibiotics?
There must be some bacteria that are resistant already. The antibiotics will kill the
non-resistant bacteria and the resistant bacteria will be the only ones left to
replicate. They will eventually build up and become greatly populated.
2) Suppose that long ago there was a population in Northern Michigan with three kinds
of hares (rabbits):
 Hares that were white ALL the time
 Hares that were brown ALL the time
 Hares that were white in the winter and brown in the summer
Explain how natural selection and reproduction would change the population over time.
The rabbits that change color will have a better survival rate than the other rabbits
because they can blend in with their environment better. With a greater survival rate
comes more reproduction. More reproduction means more traits passed onto the next
generation. Eventually the solid rabbits will die off and only rabbits that change color
will survive.
3) It is thought that the ancestors of cheetahs could only run 20 mph. Now cheetahs
have been seen running 60 mph. How would a scientist explain how cheetahs gained
the ability to run raster?
There must have been a cheetah that was faster than the rest. This cheetah had an advantage
over the other cheetahs and could survive better. With better survival comes more reproduction
and passing of ‘fast genes.’ This will happen over time and eventually the overall population will
become faster.
Analysis:
I was able to get a pre and post assessment of my students. In the pictures of their work,
the bottom answers are the post assessment. When it comes to the bacteria question, the students
seemed to struggle. The pre answers referred to the bacteria as ‘becoming immune, learning
how to avoid antibiotics, and only experiencing a small amount of antibiotics.” Even though
there was not a lot of detail some students showed some value in their answers. Sarah mentioned
‘over years’ in her explanation showing that she understands that it takes a lot of time for a
population to change. Ian said that little amounts of antibiotics could cause resistance. This
could reflect his experience with needing to take all of his medication when he was sick even
though he was feeling better. As for the post answers for question one there was improvement.
Both Ian and Sarah mentioned genes being passed onto the next generation. Adam did not
mention genes being passed on but he did mention that the bacteria needed to reproduce and pass
on ‘resistance.’ It seems that the students missed the mechanism of natural selection in this
question. They do not mention the idea that antibiotics kill the non-resistant bacteria and create
an optimum environment for the resistant bacteria.
For the second question, Sarah and Ian both said that the all brown and all white rabbits
would breed to create a rabbit that would change color in their pre questions. Adam however
mentioned that the all brown and all white rabbits would die and go extinct because they could
not camouflage all year round. He did not mention traits being passed down to each generation
but he did bring up the idea of the environment selecting for certain traits. The three students
should mixed results when it came to improving their answers for the rabbit question. Sarah
stated that the solid color rabbits would die off because ‘they could not camouflage as well as the
rabbits that change color.’ Adam did not show any improvement with this question. He pretty
much wrote the same answer. Ian showed no improvement and still said that the white rabbits
would breed with the brown to create a rabbit that changed colors. It is clear that the students are
not thinking about the mechanisms of natural selection. They are not mentioning how rabbits
pass on their genes to the next generation. It is safe to say that they understand the benefits of
camouflage with survival but they are missing the increase in traits that a population experiences.
The majority pre-answers for the cheetah question simply state that he cheetahs learn or
start to run faster to catch prey. This question showed the most progress. The second answers
contained explanations about genes being passed on over time. Sarah specifically said “one
cheetah mutated or adapted and then passed its genes to its offspring. Over time the population
grew until it was the only one left.” This is a pretty good explanation. She does not really
mention the environmental element but she seems to have some idea of how traits arise in a
population based on this answer. Adam simply wrote, “When a fast running cheetah was born, it
passed on its genes to the other cheetahs.” Again, he misses the idea that the environment selects
for this trait and other cheetahs are surpassed by the fast ones. Ian’s answer is a little unclear.
He does however mention that the genes are passed on. He does not explain how the trait arises
or the environment effects the frequency of genes being passed on.
All in all the student showed some improvement but they are not yet able to explain how
natural selection can change traits in a population to the fullest extent. They seem to understand
parts of the explanation but not the entirety.