Skip to main content

Table 4 Rubric for evaluating questions about Performing natural selection

From: Performing Evolution: Role-Play Simulations

Question

C

Quality of student work. Student…

How does this simulation illustrate heritable variation in a population?

1

S

recognizes that each round represents a new generation, and the survivors reproduce by making copies of themselves; only the surviving traits persist in the population because the variation is heritable. The other traits have gone extinct.

G

limits discussion to the fact that only the survivors can reproduce and that offspring copy a parent’s pose.

NI

recognizes that only the survivors can reproduce, but does not understand the importance of offspring copying the poses of their parents.

U

does not distinguish between heritable and acquired change.

How do you know more offspring are born than can survive?

1

S

recognizes that the predators reduce population size and that reproduction returns population size to carrying capacity.

G

knows that predators decrease population size and reproduction increases it, but does not explain why population size remains stable.

NI

knows that predators decrease the population size of prey, but does not acknowledge that reproduction increases it.

U

fails to recognize that predators decrease population size prior to reproduction.

Predict how the population would evolve if one of the tenets of natural selection did not happen. Illustrate your predictions with diagrams similar to Fig. 2. (I: overabundance of offspring; II: survival of the fittest; III: heritable variation)

1

S

modifies Fig. 2 accurately and clearly to illustrate that only I and II does not change the genetic frequency of traits; only I and III leads to random survival instead of a sorting process; only II and III cannot cause change because population size will not decrease.

G

addresses each of the three scenarios, but the illustrations reveal confusion and do not provide clear explanations.

NI

does not entertain all possible combinations. For example, the student looks only at I and II, but does not consider I and III or II and III.

U

does not form a coherent prediction or does not explain the reasoning underlying the prediction.

Why is natural selection a sorting process?

2, 3, 4

S

explicitly states that natural selection is a passive process, and explains that an environmental filter discriminates between individuals with and without a trait.

G

explains that natural selection is a filter that discriminates between individuals with and without a trait.

NI

struggles to explain what a sorting process is.

U

assumes agent of change; does not recognize that a sorting process is passive.

This simulation models selective pressure against certain traits—having a certain trait makes an individual more attractive to a predator. How would you model selective pressure towards a certain trait—having a trait that makes you less attractive to or immune to an attack by a predator?

2, 3, 4

S

recognizes that positive and negative selection are relative terms—in this model, all the traits that are not selected against are actually selected for; the same simulation works for both points of view.

G

recognizes that positive and negative selection are relative terms; struggles to illustrate this point with a simulation.

NI

recites the differences between positive and negative selection, but does not see them as two sides of the same coin and cannot apply those definitions to answer the question.

U

does not distinguish between positive and negative selection.

How and why did the frequency of the maladaptive trait change during the course of the performance?

3c, 4, 4c

S

explains that natural selection changes the frequency of a trait and can through time, provided constant selective pressure across generations, lead to the extinction of a maladaptive trait.

G

explains that natural selection changes the frequency of a trait across multiple generations, but does not discuss the extinction of a maladaptive trait.

NI

struggles with the concept of frequency or does not explain that frequency changes across generations.

U

fails to understand negative selection and relies on the common misconception that, when change occurs, it occurs to all of the individuals in the population (Gregory 2009).

What would happen if the predators’ prey preference changed? Why?

3, 3a, 3b, 3c, 4, 4c

S

recognizes that the shift in prey preference represents a shift in the environment and that the trait that had been selected against is now being selected for; similarly, a trait that had been adaptive is now maladaptive.

G

recognizes a new selective pressure, and that the trait that had been selected against is now being selected for; does not generalize that changing prey preference is a form of environmental change.

NI

recognizes a new selective pressure, but cannot predict the outcome of the change.

U

argues that it is impossible to predict.

What would happen if you added a second species of predator with a different prey preference?

2, 3, 3a, 3b, 3c, 4, 4a

S

recognizes that the second predator is a type of environmental change that causes a trait that had been adaptive to be maladaptive; natural selection would happen more quickly in this simulation, because more prey would die during each round.

G

recognizes that two selective pressures are now present and that a trait that had been adaptive is now maladaptive, but does not recognize the change in rate of natural selection.

NI

recognizes that a second trait is maladaptive, but cannot predict how the prey population will respond.

U

argues that it is impossible to predict.

Why do some individuals with maladaptive traits re-enter the population? At what point does this stop?

4d

S

recognizes that all of the survivors reproduce, even those who have the maladaptive trait; may point out a limitation in the exercise that differential reproduction is not considered.

G

recognizes that all of the survivors reproduce, even those who have the maladaptive trait.

NI

observes that the predators did not consume all of the attractive prey, but does not acknowledge that some of these survivors may reproduce.

U

invokes another mechanism of evolution, arguing that maladaptive traits cannot exist in the population if natural selection is occurring; does not recognize that natural selection changes the frequency of a trait in a population.

If the environment remains stable, and natural selection is occurring, what happens to the number of variants over time? Why?

4b

S

recognizes that natural selection decreases the amount of variation in a population because individuals with the maladaptive trait eventually go extinct.

G

recognizes that natural selection decreases the amount of variation in a population because individuals with the maladaptive trait die, but does not acknowledge that these traits are completely extinct.

NI

states that natural selection decreases the amount of variation but does not explain why.

U

states that the number of variants stays the same or increases; fails to justify answer.

How and why did your predictions about which trait was being selected change during the course of the performance? What traits hitchhiked along with the trait that was being selected against?

5a

S

recognizes that reasonable hypotheses about which trait was under selection had to be rejected; revises hypothesis during the performance by observing the poses that were selected by predators; draws from rejected hypotheses to identify traits that hitchhiked.

G

revised hypothesis during the performance and identifies traits that hitchhiked; does not explicitly analyze the data from the performance.

NI

recites a definition of hitchhiking, but does not draw on the performance to explain the definition.

U

fails to thoughtfully contemplate on the data and does not demonstrate an understanding of hitchhiking.

  1. Abbreviations as in Table 3