Evolution is often a difficult subject for students to grasp, even putting aside politics and religion. It’s also a very important concept to understand biology. Unfortunately, less than 50% of undergraduate students understand the basics of natural selection. “Nothing in biology makes sense except in the light of evolution,” wrote evolutionary biologist Theodosius Dobzhansky – but for many students, nothing in biology makes sense except in piecemeal, anticipating the next quiz. This might be because evolution tends to be taught in discreet pieces with “classic” examples: natural selection in dark- versus light-colored moths, or speciation in Darwin’s finches.
A recent study found that students who were taught using integrative case studies of evolution had a better understanding of evolutionary principals than students who were taught piecemeal examples. Fragmented examples of evolution apparently make it harder for students to understand the process of evolution as a whole.
Evolution is incredibly complex. A full understanding of evolution requires students to span topics from cellular and molecular biology to ecology. At the undergraduate level (or, if you’re lucky, in high school), teachers often focus on variation and natural selection. A classic example of natural selection is the peppered moth – light colored moths are easier for birds to see (and then eat) on dark colored trees and vice versa, so eventually light colored peppered moths are more commonly found living on light colored trees and dark colored peppered moths on dark colored trees (or soot-covered urban environments). But the genetic causes of this color variation in the moth aren’t discussed, so that piece of the story becomes a “black box” to students.
Researchers at Michigan State University tested the idea that students who used a curriculum that tracks the evolution of traits from molecular genetics to variation in a population’s phenotypes (the end result of an individual’s genes) would end up with a better overall understanding of evolution. The researchers developed a set of case studies (designed for undergraduate students) that decompartmentalize the teaching of evolution and introduce molecular and cellular mechanisms. Each case illustrates evolutionary processes by beginning with a DNA mutation (such as a change in an animal’s color) and ending with “the fixation of alternate phenotypes in separated populations” (such as the establishment of light-colored animals in light-colored environments).
Pre- and post-tests of students’ understanding of evolutionary principals showed overall improvement, and that the curriculum accounted for 40% of the difference between tests. While encouraging, over half of students’ performance is unaccounted for and – most daunting for K-12 teachers wanting to apply this curriculum – the content of their courses is much more rigorous than your average “Biology 101” class. Take a look at this pre-test question from the study:
1. Jaguars (large predatory cats) can have an orange coat or a black coat. Orange jaguars have either two G alleles (genotype GG) or one G allele and one g allele (genotype Gg), whereas black jaguars have two g alleles (genotype gg). When a jaguar has the genotype gg, what happens so that a black coat is produced?
Here’s hoping some professional development materials are in the pipeline from the authors!
Power Point slides and simulation games to help teach their case studies can be found at www.evo-ed.com.