Ready, Set, Go Evolution!
Have you ever wondered why manatees have toenails?
Do they use them to dig in the sand?
Or maybe to scratch their itchy spots?
The fourth grade students participating in the Evolution Readiness project in Massachusetts, Missouri, and Texas know why. Manatees evolved from an ancestor that had toenails — a common ancestor that they share with elephants! While their toenails have no practical function, they remain as a reminder of their terrestrial ancestors. Demystifying concepts like common ancestry is just one of the many objectives of the Evolution Readiness project.
Models address complex concepts
The Evolution Readiness project seeks to support elementary schoolchildren in acquiring the prerequisite concepts necessary for understanding the theory of evolution by natural selection. Funded by the National Science Foundation, this project is being conducted by the Concord Consortium in collaboration with researchers at Boston College’s Center for the Study of Testing, Evaluation, and Educational Policy. Our team has developed computer-based models, classroom activities, and assessment materials based on a progression of learning goals that elaborate the existing science standards and detail a series of concepts that are instrumental in understanding evolution.
Confronting fourth grade students directly with the fundamental concepts of evolutionary theory — e.g., descent with modification — would most likely generate quizzical looks and downright confusion. Constructing a full understanding of evolution is a step-by-step process. The purpose of our curriculum is to provide engaging activities, hands-on experiences, and computer models that make each step fun for students and easy for teachers. Thus, our big ideas are broken down into smaller goals, which are addressed in both classroom activities and computer-based activities.
In the 2009-2010 implementation, students were presented with five offline activities and five computer activities, focused on evolution in plants. Each computer activity contains two or three scaffolded models used to experiment with specific concepts such as variation, heritability, and selection pressure. Students began by learning about the life cycle of flowering plants. In the classroom, they planted seeds from FastPlants and watched the seedlings mature into adult plants. In parallel, on the computer they planted virtual seeds from several varieties of "Mystery Plants," and discovered that variation in the plants allowed some individuals to survive in different environments. This simple but important concept is just one of many blocks needed to build a solid foundation as students move closer to understanding evolution.
The Evolution Readiness activities support students as their understanding progresses through the following stages: a) move from reasoning about single organisms to reasoning about populations, b) move from thinking about populations in an environment to recognizing that each population’s environment is composed of other interacting populations, c) recognize the importance of physical and behavioral variation among the organisms in a population and its effect on relative fitness, d) understand that some of the variation within populations is heritable, and e) as a result, over many generations, populations may change as fitter organisms have more offspring and the traits that made them fitter become more frequent. This progression in understanding can be as difficult for adults as for children. Accordingly, we supported teachers with online training, classroom guides, and face-to-face workshops.
Results show significant student gains
At the start of our project there were no test instruments available that measured understanding of evolution at the fourth grade level, so we developed a Concept Inventory for Evolution Readiness, aligned to our learning goals progression. We piloted this concept inventory, which includes both multiple-choice and constructed response items, during the first year of the project and refined it to achieve high validity, reliability, and psychometric quality.
Estimates of students' knowledge of the concepts were computed for two cohorts using traditional measurements and Rasch modeling, a type of statistical analysis that determines students' understanding/ability regardless of the test difficulty. An independent means t-test showed that the second cohort of students who used the Evolution Readiness materials performed statistically significantly better than students who had not used the materials.
There was some variability in implementation among the three states, which was reflected in the magnitude of the gains from Cohort 1 to Cohort 2. Not surprisingly, for instance, the state where the curriculum was first implemented achieved the lowest gain. The lessons learned from this first implementation — through direct observation as well as teacher interviews — were used to refine the curriculum before introducing it in the other two states. The later two states benefited not only from curriculum changes, but also from an additional teacher workshop conducted on site prior to the start of the unit. We also observed a significant difference between the two states that started later, with the state with the lower baseline score showing the greatest gain.
|Cohort 1||Cohort 2||Is the difference in means significant?||Effect size|
|Mean||Sample Size||Mean||Sample Size|
Using a cohort design, we collected pre-program and post-program implementation data from the students of nine participating elementary teachers in three states. In all, we collected pre-implementation baseline data from 132 students (Cohort 1) who had not been exposed to the Evolution Readiness learning goals progression, computer-based activities, and supplemental curriculum materials. The following year, a second cohort of 186 students (Cohort 2, students from the same schools who had the same teachers as Cohort 1) was exposed to the curriculum.
To address some of these shortfalls, six additional activities have been added to the curriculum for implementation in the 2010-2011 school year. They focus on evolution through an ecology lens and cover competition for resources, selection pressure, and interdependence among the various species in an ecosystem.
The post-test demonstrated that students were able to identify particular physical traits that an organism needs to survive in a given environment, and they had a general understanding that animals obtain energy and resources by eating plants and other animals, that plants produce their own food, and that plants and animals have basic needs like air, water, light, nutrients, food, and shelter. These basic ecology topics are important to understand before delving into the mechanics of evolution. However, students had difficulty understanding the more complex evolutionary concepts: different species can arise from one species if different groups have different selection pressures; selection pressure can lead to a change in the characteristics of a population; and species adapt to changes in their environment.
In this model, students build a dam and watch as the environment changes below the dam, thus favoring one of the three types of plant, and eventually one type of rabbit that eats the plant.
Evolution as the heart of biology
Evolution occupies a place in biology akin to that of Newton’s Laws in physics. Just as the formula F = ma describes the motion of objects, so the mechanism of evolution by natural selection explains the fantastically intricate and diverse adaptations exhibited by organisms. It is curious, then, that evolution is not given a more prominent place in biology education. Arguably, it should be front and center in every biology curriculum, rather than being relegated to a section of its own at the back of the textbook.
"Nothing in biology makes sense except in the light of evolution."
Aside from the political controversy surrounding the subject—which may have caused some U.S. publishers to minimize its importance — it is also true that evolution is a particularly difficult concept to learn and to teach. It is driven, after all, by tiny variations between organisms that become amplified only after a filtering process requiring many generations. In most cases (bacterial pathogens being one obvious exception), the process takes place too slowly to be directly perceived and must, therefore, be inferred from indirect evidence such as fossils or DNA sequencing. In modern terminology, evolution is an "emergent behavior" — the unexpected outcome of many iterations of a simple process involving heritable traits that give rise to small differences in reproductive success. The model is straightforward but surprising and difficult to grasp.
Computers are very good at doing the same thing over and over very quickly, so it is natural to use them to build models that evolve through natural selection. It is a small step to adapt such models to enable students to manipulate them, experiment with them, and learn from them. Our Evolution Readiness project is demonstrating the value of this approach with very young children. This is a first step toward a broader "learning progression" that will engage older students with models that include processes such as Mendelian genetics (unknown to Darwin) as well as cutting-edge topics in molecular biology that are the subjects of current research.
In a much-quoted 1973 essay the evolutionary biologist (and Russian Orthodox Christian) Theodosius Dobzhansky wrote, "Nothing in biology makes sense except in the light of evolution. "1 Dobzhansky was reacting to anti-evolution theories such as creationism, but his statement has important implications for pedagogy as well. Arguably, it makes little sense to teach biology from anything but an evolutionary point of view. The results reported here are grounds for hope that such a goal is within reach and that, given powerful modeling tools and a teaching strategy that embraces a carefully orchestrated learning progression, students can be taught to understand and appreciate the extraordinary power of evolutionary theory as a unifying concept throughout the biology curriculum.
1 American Biology Teacher, volume 35, pages 125-129.
Camelia Rosca (firstname.lastname@example.org) is a Senior Research Associate at the Center for the Study of Testing, Evaluation, and Educational Policy, Boston College.
Laura O'Dwyer (email@example.com) is an Associate Professor in the Educational Research, Measurement, and Evaluation Department, Boston College.
Trudi Lord (firstname.lastname@example.org) manages the Evolution Readiness project at the Concord Consortium.
Paul Horwitz (email@example.com) directs the Evolution Readiness project at the Concord Consortium.