Back to Unit Page Unit Textbook Chapter Animations & Images Expert Interview Transcripts Unit Glossary Related Resources View Text Only List 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 Images Asteroid A re-creation by NASA scientists of the impact made by an asteroid 500 miles in diameter at Chicxulub, on the Yucatan Peninsula. This impact is thought to be the cause of the K/T mass extinction 65 million years ago. Biomass vs. species number Tilman's experimental data showing that productivity rose with the number of species grown in a plot Black Mamo Another animal that has gone extinct in the ¸sixth mass extinction” Cedar Creek aerial photo Aerial photo of Cedar Creek research fields at the University of Minnesota Cedar creek aerial photo Aerial photo of Cedar Creek research fields at the University of Minnesota Deer tick The tick that causes Lyme disease Greater Koa finch Mass extinctions The graph shows an approximate time line of loss of families of species from the earth during the five so-called ¸mass extinctions.” The trilobite, top left, was a victim of the extinction at the end of the Permian period, and the familiar T. rex died out with the K/T extinction 65 million years ago. Mouse Mouse with ticks on ear Mouse ear with engorged ticks Mouse ear with engorged ticks attached to it Passenger pigeon Once a common bird of eastern North America, the last passenger pigeon died in a zoo in 1914. Pie chart of species A pie chart of the hypothesized distribution of species living on earth today Spiro Spriochetes of Borelia burgdorferei, the bacterium that causes Lyme disease T. rex Illustration of Tyrannosaurus rex, a casualty of the mass extinction at the end of the Cretaceous period Tick Close-up of tick body Tick Tick on the end of a piece of grass, waving pincers, waiting to attach for a bloodmeal Tick photo The tick that causes Lyme disease Ticks Adult, nymph, and larval stages of the tick Ticks Adult, nymph, and larval stages of the tick Tree phylogeny Simple phylogeny of plants Trilobite Trilobite, a casualty of the mass extinction at the end of the Permian period

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