How to Actually Use Darwin's Natural Selection Worksheet About Rabbits
You probably came here because a teacher assigned a worksheet on natural selection using the classic rabbit fur color example, and you want the answers or at least a clear way to work through it. The basic setup usually involves a population of rabbits where dark fur and light fur are traits, and environmental changes — like snow cover or predators — shift which trait has the advantage. The worksheet typically asks you to fill in tables showing allele frequencies before and after selection, calculate survival rates, and sometimes draw a graph showing how the population changes over generations.
Darwins Natural Selection Worksheet Answers Rabbit
Here is the core pattern that repeats across most versions of this assignment. You start with a population where, say, 50 percent of rabbits have dark fur (genotype DD or Dd) and 50 percent have light fur (dd). Then something changes the environment. Often it is a reduction in snow cover, which means dark rabbits blend into the ground and light rabbits get eaten by predators more often. The key question is always: what happens to the frequency of each allele over successive generations? The answers follow a straightforward calculation chain. You count the number of dark and light rabbits surviving each generation, convert those numbers into genotype or allele frequencies, and track the shift. If the worksheet gives you raw survival data like "80 percent of dark rabbits survive but only 20 percent of light rabbits survive," you multiply those survival rates by the starting population to get the next generation's counts, then recalculate frequencies from there. I have gone through roughly a dozen different versions of this worksheet across multiple semesters. The edge case that always trips people up is when the problem introduces a heterozygote advantage or incomplete dominance. A common version will state that dark fur is dominant over light fur, but then the data shows that heterozygous rabbits actually have a different survival rate than homozygous dominant ones. Students tend to just treat Dd the same as DD and get the math wrong. The fix is to keep the genotypes separate all the way through the calculation instead of lumping them together. Work out DD survival, Dd survival, and dd survival as three distinct values before you combine them into allele frequencies.
Another detail that most worksheets gloss over but shows up on harder versions: the difference between selection acting on phenotypes versus genotypes. The worksheet will describe predators eating light-colored rabbits because they are visible against bare ground, which means selection is acting on the phenotype (fur color). But the actual evolutionary change happens at the allele level. If you want to show real understanding on your paper, note that distinction. It is what separates a surface-level answer from one that actually demonstrates you understand the mechanism. If your version of the worksheet asks for a Hardy-Weinberg calculation, use the standard p² + 2pq + q² = 1 framework. Start by finding q² from the frequency of the recessive phenotype (light fur rabbits), then take the square root to get q, subtract from one to get p, and work forward from there. The trap here is rounding too early. Keep at least four decimal places through intermediate steps and round only on the final answer, or your allele frequencies will drift and look wrong even though your method is sound. For the graphing portion, most teachers want you to plot allele frequency or phenotype frequency on the y-axis against generation number on the x-axis. Dark fur frequency should trend upward if the environment favors it, and light fur should trend downward. The curve is usually exponential in shape during the early generations and then flattens as the advantageous allele approaches fixation. Pointing out that flattening effect and explaining that it happens because the allele is becoming rare and selection becomes less efficient is worth extra credit on almost every rubric I have seen.
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The worksheet also sometimes asks a question about whether evolution has occurred. The answer is yes, evolution has occurred because the allele frequencies in the population changed over time. That is the textbook definition of evolution in this context. Do not overcomplicate it. The students who lose points are the ones who write paragraphs about adaptation without directly answering whether allele frequencies changed. If you are downloading a PDF of this worksheet, most school district sites or educational repositories like Share My Lesson or Teachers Pay Teachers have the standard version. Look for one that includes a data table with at least three generations and a question asking for a prediction beyond the given data. Those are the versions that actually test understanding rather than just rote calculation. One practical note: if your teacher uses a version where the environment reverses mid-problem — snow returns partway through the generations — do not assume the previous trajectory continues. Recalculate from the new selection pressures starting at the generation where the change occurs. I have watched students carry forward old frequency values into a reversed scenario and end up with impossible results like allele frequencies exceeding 100 percent.
The underlying concept here is straightforward even when the math gets fiddly. Natural selection works on existing variation in a population. When the environment changes, traits that were neutral or even harmful can become advantageous, and the population shifts toward those traits over generations. The rabbit worksheet is just a simplified model of that process. If you understand that mechanism, the calculations become mechanical rather than mysterious.
