Going to the Dogs: Exploring Allometry and Heterochrony

Rowan Lockwood
,
The College of William and Mary
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Summary

This activity explores the relationship between developmental biology and macroevolution by focusing on how evolutionary changes in ontogeny can produce small-scale (within species) and large-scale (between species or major lineages) evolution of morphology.

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Context

Audience

Undergraduate elective upper-level course in paleontology

Skills and concepts that students must have mastered

- Understanding of basic processes and terminology associated with isometry and allometry
- Understanding of basic processes and terminology associated with heterochrony
- Basic graphing skills

How the activity is situated in the course

In class lecture or lab activity (25-50 minutes depending on depth of discussion)

Goals

Content/concepts goals for this activity

- heterochrony (paedomorphosis vs peramorphosis)
- isometry and allometry (positive vs negative)
- macroevolutionary processes

Higher order thinking skills goals for this activity

- data collection and interpretation

Other skills goals for this activity

- graphing skills

Description of the activity/assignment

In this activity, students explore the relationship between developmental biology and macroevolution by focusing on how evolutionary changes in ontogeny can produce small-scale (within species) and large-scale (between species or major lineages) evolution of morphology.

In Part A, students begin the activity by measuring skull length vs. braincase width in an ontogenetic sequence of an "ancestral" wolf species. They graph the resulting data then determine whether the relationship between the two is isometric or allometric.

In part B, they choose three skulls of adult domestic dog breeds (available via online sources such as Skulls Unlimited). Measure the same two variables and compare these "descendent" data to the wolf "ancestral" data. In this way, they determine which dog breeds (e.g., pugs, bulldogs) appear to be paedomorphic and which (e.g., greyhounds) appear to be peramorphic.

Determining whether students have met the goals

I grade this assignment using a simple 10pt scale, based on how well the students collected their data, graphed it, interpreted it, and answered the discussion questions.

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