HHMI Data Point: Effects of Natural Selection on Finch Beak Size

Contributor
HHMI Biointeractive Bob Kuhn
Type Category
Instructional Materials Assessment Materials
Types
Instructor Guide/Manual , Assessment Item , Article , Data
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

Reviews

Description

Effects of Natural Selection on Finch Beak Size is one of a series of Data Point resources from HHMI Biointeractive.  Data Points engage students in analyzing and interpreting data from primary literature in the biological sciences.  The resources are intended to provide authentic phenomena to spark student discussion and exploration, but they can also serve as three-dimensional assessment items.  In this example, students analyze the effects of a drought on the distribution of beak sizes in a population of ground finches in the Galapagos Islands.

Intended Audience

Educator
Educational Level
  • Grade 12
  • Grade 11
  • Grade 10
  • Grade 9
  • High School
Language
English
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-LS4-4 Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment.

Clarification Statement: Emphasis is on using simple probability statements and proportional reasoning to construct explanations.

Assessment Boundary: none

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
By presenting data before and after an environmental change (i.e., drought), this Data Point does a good job of focusing students’ attention on the process of natural selection leading to adaptation of a population (i.e., change in beak depth in a finch population in response to a change in seed availability after the drought). The discussion questions reinforce this connection by asking students to explain why the population surviving the drought exhibited a larger mean beak size and to predict how this would be reflected in their offspring. The teacher can then help students link this shift to the population’s ability to survive in future years. The Educator Guide and the linked research article both provide important background information to support the teacher in making this link.

HS-LS4-3 Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.

Clarification Statement: Emphasis is on analyzing shifts in numerical distribution of traits and using these shifts as evidence to support explanations.

Assessment Boundary: Assessment is limited to basic statistical and graphical analysis. Assessment does not include allele frequency calculations.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
The bar graph and supporting information provided in the Data Point highlight a key concept from a rich research article based on a long-term study of evolution in Galapagos finches. By overlaying data from two years, the bar graph helps students focus in on the effect that an environmental change can have on a population of organisms. In addition to representing the numerical distribution of beak sizes, the graph also represents the mean for this trait in each year. These features will facilitate students’ ability to identify patterns in the data. This resource provides an excellent opportunity to engage students in basic statistical reasoning as it relates to evolution within a population.

HS-LS4-2 Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.

Clarification Statement: Emphasis is on using evidence to explain the influence each of the four factors has on number of organisms, behaviors, morphology, or physiology in terms of ability to compete for limited resources and subsequent survival of individuals and adaptation of species. Examples of evidence could include mathematical models such as simple distribution graphs and proportional reasoning.

Assessment Boundary: Assessment does not include other mechanisms of evolution, such as genetic drift, gene flow through migration, and co-evolution.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
This Data Point could serve as an opening phenomenon to spark student learning leading up to this Performance Expectation or as an assessment of the Performance Expectation. The resource is framed as a discussion starter in which students are asked to analyze graphical data and develop an explanation of that data. The Educator Guide provides extensive background for teachers and a set of discussion questions to guide students toward developing an explanation of the role that natural selection has played in the short-term evolution of Galapagos ground finches. The authentic scenario and data presented in the resource provide strong links to the four factors listed in the Performance Expectation.

Science and Engineering Practices

This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.

Comments about Including the Science and Engineering Practice
This Data Point is framed as a discussion starter, and the Educator Guide provides discussion questions that guide students toward developing an explanation. However, the resource offers good potential to meet this practice directly. Whether used as an opening phenomenon or as an assessment, the teacher could use the provided discussion questions as the basis for students to develop formal explanations that draw on the data provided, as well as other student learning experiences. In particular, this resource offers an excellent opportunity to begin a lesson or unit in which students work toward constructing an explanation of how factors of natural selection lead to adaptive changes in populations (i.e., Performance Expectations HS-LS4-2 and HS-LS4-4).

This resource appears to be designed to build towards this science and engineering practice, though the resource developer has not explicitly stated so.

Comments about Including the Science and Engineering Practice
The goal of the Data Points series is to engage students in analyzing and interpreting data from primary sources. To provide full context for teachers and potentially for students, this data point is accompanied by a link to the original research article (http://bioscience.oxfordjournals.org/content/53/10/965.full.pdf+html). This Data Point calls for students to apply statistical reasoning to examine the effect of a drought on the beak sizes of ground finches in the Galapagos Islands. As the Educator Guide suggests, the graph provides an opportunity for students to develop or apply their understanding of data distributions and means. For advanced classes, teachers might want to pull additional graphs from the original research article to supplement content and statistical understanding. For example, Figure 6 in the article presents graphs of changes in beak sizes over 30+ years and includes 95% confidence interval bars for each data point. For teachers who would like more background information on teaching mathematics and statistics in biology, HHMI offers the Teacher Guide: Math and Statistics (http://www.hhmi.org/biointeractive/teacher-guide-math-and-statistics).

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
This Data Point provides a good opportunity for students to begin an exploration of how genetic, reproductive, and environmental factors can lead to evolution within populations. The graph and brief background information provided to students will provide a foundation for this exploration, but students would benefit most from additional learning experiences, either following or leading up to the Data Point. Options include having students read the original research article or conduct online research about the Galapagos finches.

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
The initial data presented in this resource sets the stage for students to develop understanding of this core idea by demonstrating the effect that a drought has on a population of finches. After asking students to make predictions about the distribution of beak sizes in offspring of the surviving finches, students are presented with actual data. This new data reveals that the distribution of beak size from the parental population is reflected in the offspring. Thus, students are able to observe directly the accumulation of a beneficial trait in a population across generations. The original research article offers additional, long-term data, and the teacher might incorporate that data into additional learning experiences for students.

Crosscutting Concepts

This resource was not designed to build towards this crosscutting concept, but can be used to build towards it using the suggestions provided below.

Comments about Including the Crosscutting Concept
By overlaying data for the finch population before and after the drought, the graph draws students’ attention to patterns in the data that will facilitate their understanding of natural selection and adaptation. The data provided for offspring reinforce these patterns, and the additional data provided in the research article offer further opportunities for students to examine patterns in long-term data. Linking these patterns to causal claims about natural selection and adaptation will require students to develop broader understandings about the finches and their environment. Additional learning experiences can provide support for this understanding and provide opportunities for students to build toward other evolution-related Performance Expectations. For example, the original research article includes a discussion of DNA data analysis that has illuminated the common ancestry and descent of the Galapagos finch species. By examining this data, students can make the connection between patterns observed at various scales (i.e., DNA within individual organisms versus beak size data across a population).

This resource was not designed to build towards this crosscutting concept, but can be used to build towards it using the suggestions provided below.

Comments about Including the Crosscutting Concept
The discussion questions provided in the Educator Guide focus student attention on identifying cause-effect relationships based on the data presented. This could be strengthened by asking students specifically to consider whether the evidence provided is sufficient to support causal claims, rather than simply showing correlation between variables. To do so, students will need to develop and apply contextual knowledge about the finches and their habitats.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This Data Point provides opportunity for analysis of data about an authentic phenomenon that could anchor a series of three-dimensional learning activities. In this case, a preliminary discussion would allow the teacher to expose students’ initial ideas before facilitating student exploration of the phenomenon through additional learning activities. Alternatively, this resource could be used as an assessment item. In either case, the resource may be strengthened by combining it with other learning experiences. For example, this resource could be combined with HHMI’s The Origin of Species: The Beak of the Finch (http://www.hhmi.org/biointeractive/origin-species-beak-finch) to develop a unit that addresses a bundle of evolution-related Performance Expectations. A second example that draws on the same primary research article is the "Darwin's Finches and Natural Selection case study from the National Center for Case Study Teaching in Science (http://sciencecases.lib.buffalo.edu/cs/collection/detail.asp?case_id=550&id=550). The Data Point resource strongly aligns to the indicated Disciplinary Core Ideas and Science and Engineering Practices, but teachers can strengthen these connections through the additional learning experiences. The alignment to the Crosscutting Concepts is less explicit, but the teacher can draw students’ focus to these connections with guiding questions or learning experiences that help students link the process of natural selection to the adaptations observed in finch populations.

  • Instructional Supports: By using data from a primary source, this Data Point provides an excellent, scientifically accurate context in which students can engage in three-dimensional learning. This resource is written as a discussion prompt, and a whole-class discussion would provide one venue for the teacher hear student ideas and give feedback on those. However, the resource is not a full lesson. As a result, it does not provide a full range of instructional supports, such as opportunities for students to build on feedback, guidance for differentiation, and scaffolds to support students in engaging in practices or applying crosscutting concepts. The teacher will need to incorporate these supports while building a full instructional sequence around this resource.

  • Monitoring Student Progress: Whether it is used formatively or summatively, the Data Point,offers an excellent opportunity to gather evidence of students’ three-dimensional learning. Although the data is pulled from a primary research article, the selection of data and the supporting information provide much greater accessibility than the original research article. A rubric is not provided, but the Educator Guide does provide the background information needed to assess and support student responses. The teacher may want to to consider embedding formative assessments and developing associated rubrics when planning a full instructional sequence.

  • Quality of Technological Interactivity: This is not an interactive, technology-based resource, although the link to the original research article does enhance the value of the resource.