1. Traditional levels of biological organization

Biologists usually limit their study to one of these levels of organization:

macromolecule, organelle, cell, tissue, organ, organ system, individual, population, species, community, ecosystem, landscape, biome, biosphere

Do these levels exist outside of our perception? If so, how do they come about?

2. Some concrete examples of scale-dependence in ecology

• Ecological variables show different variability at different resolutions.
•  carbon figure
•  soil organic matter figure
•  zooplankton figure
• classic measure-the-coastline problem
•  fractal landscape figure
• metapopulations and patch dynamics
•  spotted owl figure
•  Jasper Ridge model figure
• dispersal and dormancy: scale-driven selection for life-history traits
•  dispersal figure

3. Terminology

• scale (spatial or temporal)
• level of organization
• ScaleRelatedTerminology

4. Putting it all together

4.1. How ecosystem science (informed by hierarchy theory) puts everything together

• Nature is a bunch of processes which do or don't interact directly.
• Every process has a characteristic rate.
• Some processes are faster than others.
• Slower processes "see" faster ones as the faster processes'  averages.
• Example: we don't perceive molecules' motion, just temperature.
• Example: plant growth doesn't respond to millisecond-level fluctuations in photosynthetic rate, just to hour-level carbon captured.
• Faster processes "see" slower ones as constants.
• Example: we don't see continents moving and treat them as stationary.
• Example: Photosynthetic rate depends on leaf-display architecture, but no photosynthetic enzyme senses leaf display.
• Because processes with very different rates can't pass full information, their effects on each other are asymmetrical.
• Levels of organization are defined by the different rates.
• Phenomena at one level have mechanisms in lower-level (faster) processes and constraints in higher-level (slower) processes.

4.2. How most ecologists these days might differ from that, if they thought about it

• Ecological phenomena have variation which itself varies with scale. There is no one characteristic scale for any process.
•  disturbance regime figure
• Organisms (or populations or cells or whatever entities at whatever level) perceive relevant processes at a particular scale.
• So even though there's no one scale, there is one relevant scale. The appropriate scale depends on what problem you're studying.
• Start with the relevant entity: organisms (or whatever) are  donuts, and nature is a bunch of interconnected donuts.

5. What it means for the Emergenauts

• Level of organization is all about scale. Natural phenomena can be broken down into processes that are separated from each other by the barriers between levels.
• Scale may be in the eye of the beholder, but butterflies, trees, and chemical reactions are themselves beholders -- so scale has biological relevance independent of us.

6. Websites people mentioned during the discussion

•  Powers of Ten (suggested by Karen)
•  "In the Vastness of Space" by Walter Alvarez (suggested by Paul)
•  Java-zoomable Powers of Ten (suggested by Don)
• It's a Wiki -- add your own!

7. Readings

• Levin, S. 1992. The problem of pattern and scale in ecology. Ecology 73(6):1943-1967.
• O'Neill, R.V. et al. 1986. A Hierarchical Concept of Ecosystems. Princeton Univ. Press, Princeton, N.J.
• Turner, M.G. 2001. Landscape Ecology in Theory and Practice. Springer-Verlag, New York.
• Allen, T.F.H. and T.W. Hoekstra. 1992. Toward a Unified Ecology. Columbia Univ. Press, New York.

8. Figure sources

• "Jasper Ridge figure," "dispersal figure" and "zooplankton figure" from Levin.
• "averages" from O'Neill et al.
• "donut" from Allen and Hoekstra.
• "spotted owl figure" from www.fw.umn.edu/Research/Owls/Cal_owl_SanBern.htm
• "carbon figure" from all over the web
• All other figures, as well as terminology table, from Turner et al.