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Macroevolution: Evolution above the Species Level

Co-sponsored by the Biological Sciences Curriculum Studies and the National Evolutionary Synthesis Center
October 14 2006

National Association of Biology Teachers Conference, Albuquerque, NM

Description

On October 14th, AIBS continued its tradition of hosting a symposium on evolution at the NABT annual conference with its co-sponsors: the Biological Sciences Curriculum Studies (BSCS) and National Evolutionary Synthesis Center. The theme of the 2006 symposium was Macroevolution: Evolution above the Species Level. Presentations in the symposium provided current information about macroevolutionary processes, the distinctions between and the interactions of micro- and macroevolution, the development and evolution of "key innovations" and major lineages of organisms, and the evidence for these processes.

In addition to six presentations from evolutionary biologists, the BSCS presented classroom activities which used the 5E model: Engage, Explore, Explain, Elaborate, and Evaluate. The 5E model is based a constructivist approach to teaching which encourages students to take an active role in learning.

Symposium Schedule and Program

14 October, 2006


8:30

Introduction to Symposium
 

8:45 - 9:15

From Protozoa to Metazoa: the Origin of Animal Multicellularity

Nicole King, Departments of Integrative Biology and Molecular and Cell Biology, University of California, Berkeley, CA; website

All multicellular animals trace their heritage back to a single-celled common ancestor. The origin of animals and the transition from unicellularity to multicellularity represent pivotal events in the history of life on earth. King will describe how the study of unique protozoa called choanoflagellates provides unexpected insights into the genetics and biology of the first multicellular animals.
 

9:15 - 9:45

The Developmental Basis of Animal Diversity

Nipam Patel, Departments of Integrative Biology and Molecular and Cell Biology, University of California, Berkeley, CA; website

Biologists understand many of the molecular mechanisms that control animal development. Combining this with comparative approaches, we can now begin to understand the evolutionary mechanisms that generated the diversity of extant animals.
 

9:45 - 10:00

Question and Answer

10:00 - 10:45

BSCS Activity 1: Species: An Evolving Concept

Participants explore the concept of species. They start with a text book definition and assess its strengths and limitations. The concept of species is viewed from a variety of biological perspectives. Biological examples are presented that illustrate the difficulty in using a simple definition for species.
 

10:45 - 11:00

Break

11:00 - 11:30

The Cambrian Explosion and the Nature of Evidence

Jeffrey S. Levinton, Marine Ecology Laboratory, Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook, NY; website

Was there a Cambrian explosion of animal life? The fossils generally point to a sudden occurrence near the beginning of the Cambrian whereas the molecular clock evidence points to an earlier divergence.
 

11:30 - 12:00

Evolutionary Role of Extinctions and Recoveries in the History of Life

David Jablonski, Department of Geophysical Sciences, University of Chicago, Chicago, IL; website

The fossil record is punctuated by extinction events at all scales, and at least 95% of the species that have ever lived are extinct. A relatively small proportion of this extinction is concentrated in the "Big Five" mass extinctions, geologically brief events (probably <1 million years) that are global in scale, are estimated to remove >50% of living species, and affect a broad spectrum of organisms. Mass extinctions are important in macroevolution for two reasons. First, they remove dominant groups, apparently because the rules of survival can change during the mass extinctions (e.g., the end-Cretaceous demise of the dinosaurs, which dominated the earth for the first 2/3 of mammalian history). Second they promote post-extinction evolutionary bursts (as with the post-dinosaur mammals); however, not all survivors are winners, so the dynamics of recoveries (still poorly understood) are important in shaping the post-extinction world.
 

12:00 - 12:15

Question and Answer

12:15

Break for Lunch

1:30 - 2:15

BSCS Activity 2: A Step in Speciation

Participants act as scientists trying to decide whether different populations of salamanders living in California constitute different species or subspecies. They analyze morphological and geographical data to make their determinations.
 

2:15

Break

2:30 - 3:00

Fossils and the Origin of Whales

Philip Gingerich, Museum of Paleontology and Departments of Geological Sciences, Biology, and Anthropology, The University of Michigan, Ann Arbor, MI; website

Fossils document biological change through geological time. New fossil whales document a transition from land to sea once thought inexplicable in terms of evolution.
 

3:00 - 3:30

The Generation of Plant Biodiversity: Linking Historical Patterns with Evolutionary Processes

Scott Hodges, Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA; website

An obvious macroevolutionary pattern is that some groups of organisms contain huge numbers of species while others are represented by only a single species. Understanding if there are biological processes or features responsible for these differences is thus an important goal. Differences in diversity arise through variation in the rates of speciation and/or extinction, though random processes can also cause large differences in species diversity. One way to test whether a trait has affected species diversity is by making multiple sister-group comparisons. The evolution of floral nectar spurs is one such trait that is significantly correlated with increased species diversity in groups that possess them compared to their non-spurred sister groups. Finding this association suggests that nectar spurs affect the process of speciation or extinction. Nectar spurs may affect speciation by allowing plants to specialize on different pollinators and become reproductively isolated. This hypothesis can be tested with extant species and thus we can link the historical pattern of species diversity with current evolutionary processes.
 

3:30

Question/Answer

3:45

Closing Remarks

Kathleen Smith, Director, National Evolutionary Synthesis Center (NESCent), Durham, NC; website

Contact

For more information, contact Susan Musante at or 202-628-1500 x 206.

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