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Rediscovering Biology: Molecular to Global Perspectives


With current extinction rates exceeding those of previous mass extinctions, many biodiversity studies focus on efforts to count Earth’s species before they are lost. This unit explores current field experiments studying complex ecosystems, and examines our moral responsibilities as the world’s most influential species.

The online textbook chapters support and extend the content of each video. The Web version can be viewed as a full chapter or as individual sub-sections, and includes links to glossary terms and other related material.

Explore the archive of animations, images and figures from the videos and online textbook. All of the images can be viewed online or downloaded as jpg files.

Read profiles of the expert scientists featured in the video and find the complete transcripts of the interviews conducted for this unit.

James Miller, PhD
Rick Ostfeld, PhD
Peter H. Raven, PhD
Eleanor Sterling, PhD
G. David Tilman, PhD

Chapter Contents

What is Biodiversity and Why Should We Conserve It?
Global Species Diversity
The Erwin Study
Seven Kinds of Rarity
What Factors Determine Extinction Probability?
Keystone Species and the Diversity-Stability Hypothesis
Mass Extinctions
The Sixth Mass Extinction

Unit Glossary

A method of gene transfer that occurs in bacteria, in which DNA copied from a plasmid or chromosome is transferred to a recipient cell. It can contribute to lateral gene transfer when it occurs between distantly related bacteria.

The phenomenon where more distantly related lineages have similar features due to the operation of similar evolutionary forces.
The total diversity of all life in a given locale.
Demographic stochasticity
Variation in numbers or genders of offspring via chance. When population sizes are low, these chance factors can lead to extinction.
Diversity-stability hypothesis
Communities that contain more species will vary less through time in response to various disturbances.
Keystone species
A species whose presence has a dramatic effect on the persistence of other species.

Unit Animations

  • Dilution effect
    As suburbs developed in New England, the forest habitat became more patchy, resulting in the disappearance of some species and the proliferation of mice — which are the reservoir for the Lyme spirochete — and ticks, which carry the disease to humans. This increased the proportion of infected ticks, and led to an increase in human disease.
    View Quicktime Movie
  • Mass Extinctions
    A graph showing the five major recognized mass extinctions over the last 600 million years. Trilobites went extinct at the end of the Permian era, while dinosaurs were casualties of the most recent mass extinction at the Cretaceous/Tertiary period border.
    View Animation Still
  • Species Richness vs. Lyme Disease
    Ostfeld’s study found that as species richness declined, the incidence of Lyme disease increased.
    View Animation Still
  • Test Strip – Cedar Creek
    Each year, David Tilman collects the plant matter from a strip 10 cm by 3 m from each of his experimental plots to examine the effects of species diversity on biomass.
    View Animation Still
  • Tilman’s Experimental Plots
    Tilman compares plots with few species (on left) to those with more species (as on the right). He has found that more diverse plots recover from disturbances like drought more quickly than those with fewer species.
    View Animation Still

Related Resources

Dobson, A. P. 1998. Conservation and biodiversity. New York: Scientific American Library.
An accessible summary about biodiversity from one of the leaders of the field.

Levin, S. A. 1999. Fragile dominion: Complexity and the commons.Cambridge, MA: Perseus Books.
Discussion about ecology, complexity theory and approaches to modeling complex systems.

Reaka-Kudla, M. L., D. E. Wilson, and E. O. Wilson (eds). 1997. Biodiversity II: Understanding and protecting Our biological resources. Washington, D. C.: Joseph Henry Press.
A multiauthored volume on various aspects of quantifying and preserving biodiversity.

Wilson, E. O. 1994. Naturalist. Washington, D. C.: Naturalist Warner Books
The autobiography of a prominent ecologist and one of the founders of the field biodiversity.

Series Directory

Rediscovering Biology: Molecular to Global Perspectives


Produced by Oregon Public Broadcasting. 2003.
  • ISBN: 1-57680-733-9