De-Evolution
An Extended Case Study for SCI 105
Prepared by Brian E. Rood
For SCI Summer Workshop 2004
Background:
Niche theory suggests that there will always be some life form that will fill the “n-dimensional hypervolume” (i.e. the complex set of environmental conditions) that develops in any macro- or micro-habitat among the vast array of assemblages that occur in the Earth’s biosphere. Examining the unique forms of life that proliferate in the most extreme environments on the planet’s surface provides insight to the extent of adaptability of life on this planet. Further, because these extreme environments represent those parts of the Earth’s biosphere that scientists currently recognize as the “fringes” of inhabitable space, researchers make inferences that the life processes that occur in these zones may represent the most primitive strategies of “life” on this planet.
Vestiges of bioenergetic evolution are revealed perennially in aquatic systems. Limnologists and ecosystem evolution scientists recognize that the unique annual cycling phenomenon that occurs in lakes permits investigators to observe a circumstance where physical processes combine with the activities of “life” itself to alter the conditions of aquatic environments. Ambient conditions are altered such that “higher” organisms must yield domain to “lower” organisms in a process that has been described as “de-evolution”. The process of de-evolution is on the scale of ecosystems. De-evolution is not a term that applies to adaptive changes in organisms through successive generations. Indeed, examples are provided that help to make this distinction (e.g. “The ascent of man” and vestigiality)
This case study is actually a sequence of four separate parts that hopefully have been made to be sufficiently distinct to permit the instructor either to follow the complete sequence or to use the activities and material content of a single part to suit the needs of the classroom toward addressing various learning objectives. The four parts of this case study include:
1) “Why my grandpa wasn’t a fish and why my grandma wasn’t a frog!”---
Understanding what evolution is and is not. This part will use the previously
prepared case study on evolution.
2) Physical limnology and the biological processes that we know
3) Extreme environments and responses to extreme conditions
4) The case for de-evolution
Required video:
“Deep Sea, Deep Secrets”, ISBN 371-689-5, is a Discovery Channel Video produced by Gabriel Films in association with the Woods Hole Oceanographic Institute, Distributed by Bridgestone Multimedia Group. Notes are available for this video.
Suggested or supplemental readings:
Suggested:
Knoll, Andrew H. 2003. Life on a Young
Planet.
Cairns-Smith, A.G. 1985 (Canto edition, 1998). Seven clues to the origin of life.
Supplemental:
Margulis, L., M.F. Dolan. 2002. Early Life: Evolution on the Pre-Cambrian Earth, 2nd ed.
Jones
and
Dyson, Freeman. 1999. Origins of
life, 2nd ed. Cambridge University Press.
Learning Objectives:
1) introduce the concept of modeling to understand complex systems.
2) increase sense of wonder and interest in understanding complex systems.
3) make inferences and deductive reasoning about complex systems or poorly understood systems.
4) understand natural physical, chemical, and biological phenomena in aquatic systems.
5) Examine the mathematical models and models of analogy that describe complex natural processes.
6) demonstrate critical thought and decision making at a level commensurate with accepted norms for freshman/sophomore abilities.
Activities:
“Population growth rates, mutations, evolution, and relative risk”
A hands-on group activity that uses physical media to examine
growth rates and mutations that may lead to evolutionary changes
over time.
“Aquarium model of thermal stratification…calculating RTRMs”
An aquarium-based approach to understanding the annual cycles that occur in lakes, and the implications of thermal cycles in lakes on life.
“I live on 1.5 volts, how about you?”…”Organisms as batteries”
An activity that uses batteries to elucidate our metabolic similarity to simple batteries recognizing living organisms at the cathode and the environment as the anode.
“De-evolution, the ascent (and descent) of man, and ecosystems”
An interpretive activity that examines niche theory and the assertion that lake systems and other micro- and macro-environments routinely exhibit the phenomenon of de-evolution … the vestiges of bioenergetic evolution.