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Dartmouth Scholarship

Series

2003

Articles 1 - 7 of 7

Full-Text Articles in Biology

Antipredator Behavior And Physiology Determine Lestes Species Turnover Along The Pond-Permanence Gradient, Robby Stoks, Mark A. Mcpeek Dec 2003

Antipredator Behavior And Physiology Determine Lestes Species Turnover Along The Pond-Permanence Gradient, Robby Stoks, Mark A. Mcpeek

Dartmouth Scholarship

Identifying key traits that shape trade-offs that restrict species to only a subset of environmental gradients is crucial to understanding and predicting species turnover. Previous field experiments have shown that larvae of Lestes damselfly species segregate along the entire gradient of pond permanence and predator presence and that differential predation risk and life history constraints together shape their distribution. Here, we report laboratory experiments that identify key differences in behavior and physiology among species that structure their distributions along this gradient. The absence of adaptive antipredator behavioral responses against large dragonfly larvae and fish of Lestes dryas, the only species …

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Enhancer Trapping Reveals Widespread Circadian Clock Transcriptional Control In Arabidopsis, Todd P. Michael, C Robertson Mcclung Jun 2003

Enhancer Trapping Reveals Widespread Circadian Clock Transcriptional Control In Arabidopsis, Todd P. Michael, C Robertson Mcclung

Dartmouth Scholarship

The circadian clock synchronizes the internal biology of an organism with the environment and has been shown to be widespread among organisms. Microarray experiments have shown that the circadian clock regulates mRNA abundance of about 10% of the transcriptome in plants, invertebrates, and mammals. In contrast, the circadian clock regulates the transcription of the virtually all cyanobacterial genes. To determine the extent to which the circadian clock controls transcription in Arabidopsis, we used in vivo enhancer trapping. We found that 36% of our enhancer trap lines display circadian-regulated transcription, which is much higher than estimates of circadian regulation based on …

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Predators And Life Histories Shape Lestes Damselfly Assemblages Along A Freshwater Habitat Gradient, Robby Stoks, Mark A. Mcpeek Jun 2003

Predators And Life Histories Shape Lestes Damselfly Assemblages Along A Freshwater Habitat Gradient, Robby Stoks, Mark A. Mcpeek

Dartmouth Scholarship

Survey data from New England showed that assemblages of Lestes damselflies are organized along the entire gradient of pond permanence and predator presence. One assemblage occupies vernal ponds lacking large dragonfly predators and fish; four are largely confined to temporary ponds that typically contain dragonfly predators; one dominates fishless permanent ponds and lakes where dragonflies are the top predators; and one dominates permanent ponds and lakes where fish are the top predators. We determined the role of life history and predation in maintaining this striking pattern by conducting a series of transplant experiments in the field and a laboratory experiment …

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Two Arabidopsis Circadian Oscillators Can Be Distinguished By Differential Temperature Sensitivity, Todd P. Michael, Patrice A. Salome, C. Robertson Mcclung Mar 2003

Two Arabidopsis Circadian Oscillators Can Be Distinguished By Differential Temperature Sensitivity, Todd P. Michael, Patrice A. Salome, C. Robertson Mcclung

Dartmouth Scholarship

Circadian rhythms are widespread in nature and reflect the activity of an endogenous biological clock. In metazoans, the circadian system includes a central circadian clock in the brain as well as distinct clocks in peripheral tissues such as the retina or liver. Similarly, plants have distinct clocks in different cell layers and tissues. Here, we show that two different circadian clocks, distinguishable by their sensitivity to environmental temperature signals, regulate the transcription of genes that are expressed in the Arabidopsis thaliana cotyledon. One oscillator, which regulates CAB2 expression, responds preferentially to light–dark versus temperature cycles and fails to respond to …

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Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith Jan 2003

Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith

Dartmouth Scholarship

Regulation of ciliary and flagellar motility requires spatial control of dynein-driven microtubule sliding. However, the mechanism for regulating the location and symmetry of dynein activity is not understood. One hypothesis is that the asymmetrically organized central apparatus, through interactions with the radial spokes, transmits a signal to regulate dynein-driven microtubule sliding between subsets of doublet microtubules. Based on this model, we hypothesized that the orientation of the central apparatus defines positions of active microtubule sliding required to control bending in the axoneme. To test this, we induced microtubule sliding in axonemes isolated from wild-type and mutant Chlamydomonas cells, and then …

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Richard Goldschmidt: Hopeful Monsters And Other 'Heresies', Michael Dietrich Jan 2003

Richard Goldschmidt: Hopeful Monsters And Other 'Heresies', Michael Dietrich

Dartmouth Scholarship

Richard Goldschmidt is remembered today as one of the most controversial biologists of the twentieth century. Although his work on sex determination and physiological genetics earned him accolades from his peers, his rejection of the classical gene and his unpopular theories about evolution significantly damaged his scientific reputation. This article reviews Goldschmidt's life and work, with an emphasis on his controversial views.

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The Delphic Boat: What Genomes Tell Us, Michael Dietrich Jan 2003

The Delphic Boat: What Genomes Tell Us, Michael Dietrich

Dartmouth Scholarship

A review of The Delphic Boat: What Genomes Tell Us by Antoine Danchin Alison Quayle, trans. Harvard University Press, 2003 380 pp. hardcover. ISBN 0-67400-930-4

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