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Biological Sciences

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Articles 541 - 570 of 617

Full-Text Articles in Biology

Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield Jan 1997

Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield

Biological Sciences

No abstract provided.


Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil Jan 1997

Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil

Biological Sciences

No abstract provided.


Long-Term Monitoring And Analyses Of Physical Factors Regulating Variability In Coastal Antarctic Phytoplankton Biomass, In Situ Productivity And Taxonomic Composition Over Subseasonal, Seasonal And Interannual Time Scales, Mark A. Moline, Barbara B. Prezelin Dec 1996

Long-Term Monitoring And Analyses Of Physical Factors Regulating Variability In Coastal Antarctic Phytoplankton Biomass, In Situ Productivity And Taxonomic Composition Over Subseasonal, Seasonal And Interannual Time Scales, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

A 3 yr high-resolution temporal data base related to phytoplankton dynamics was collected during the austral spring/summer periods of 1991 to 1994 in shelf waters adjacent to Palmer Station, Antarctica. Here, the data base is used (1) to quantify the variability in phytoplankton biomass, in situ productivity and taxonomic composition over subseasonal, seasonal and interannual time scales; (2) to elucidate environmental mechanisms controlling these temporal patterns; and (3) to ascertain which phytoplankton markers are most suitable for detecting longer-term (i.e. decadal) trends in phytoplankton dynamics in coastal waters of the Southern Ocean. The Long-Term Ecological Research (LTER) coastal study sites …


Genetic And Social Control Of Male Maturation In Phallichthys Quadripunctatus (Pisces: Poeciliidae), Gita R. Kolluru, David N. Reznick Nov 1996

Genetic And Social Control Of Male Maturation In Phallichthys Quadripunctatus (Pisces: Poeciliidae), Gita R. Kolluru, David N. Reznick

Biological Sciences

Age and size at maturity can have significant fitness consequences. Selection often favors early-maturing individuals because of their higher survival to maturity and greater relative contribution to population growth rate, but it may also favor delayed maturation if fitness increases with age or size at maturity. Males of several poeciliid fishes exhibit variation in age and size at maturity primarily controlled by a sex-linked gene called the P-locus. Wild-caught Phallichthys quadripunctatus males show a bimodal size distribution, which is often associated with a P-locus polymorphism in other poeciliids. We conducted two experiments to evaluate the inheritance of male age and …


High-Resolution Time-Series Data For 1991/1992 Primary Production And Related Parameters At A Palmer Lter Coastal Site: Implications For Modeling Carbon Fixation In The Southern Ocean, Mark A. Moline, Barbara B. Prezelin Nov 1996

High-Resolution Time-Series Data For 1991/1992 Primary Production And Related Parameters At A Palmer Lter Coastal Site: Implications For Modeling Carbon Fixation In The Southern Ocean, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

Our goal was to provide a high-resolution temporal data base for modeling primary production in shelf waters adjacent to Palmer Station, Antarctica. Here, the resulting 1991/1992 data base is used to: (1) determine in situ productivity over a range of seasonal to subseasonal time scales; (2) identify time scales of significant variability in marine productivity during the peak growing season; (3) identify environmental, experimental and analytical factors that can significantly impact the accuracy of daily, weekly and seasonal productivity estimates; and (4) integrate our findings with previous studies of Antarctic coastal primary pro- duction. Data were gathered every 2–3 days …


Azorhizobium Caulinodans Uses Both Cytochrome Bd (Quinol) And Cytochrome Cbb3 (Cytochrome C) Terminal Oxidases For Symbiotic N2 Fixation, Alexandre Kaminski, Christopher L. Kitts, Zachary Zimmerman, Robert A. Ludwig Oct 1996

Azorhizobium Caulinodans Uses Both Cytochrome Bd (Quinol) And Cytochrome Cbb3 (Cytochrome C) Terminal Oxidases For Symbiotic N2 Fixation, Alexandre Kaminski, Christopher L. Kitts, Zachary Zimmerman, Robert A. Ludwig

Biological Sciences

Azorhizobium caulinodans employs both cytochrome bd (cytbd; quinol oxidase) and cytcbb3 (cytc oxidase) as terminal oxidases in environments with very low O2 concentrations. To investigate physiological roles of these two terminal oxidases both in microaerobic culture and in symbiosis, knockout mutants were constructed. As evidenced by visible absorbance spectra taken from mutant bacteria carrying perfect gene replacements, both the cytbd- and cytcbb3- mutations were null alleles. In aerobic culture under 2% O2 atmosphere, Azorhizobium cytbd- and cytcbb3- single mutants both fixed N2 at 70 to 90% of wild-type rates; in root nodule symbiosis, both single mutants fixed N2 at 50% …


Two Erroneous, Commonly Cited Examples Of "Swordfish" Piercing Wooden Ships, Harry L. Fierstine, Oliver Crimmen May 1996

Two Erroneous, Commonly Cited Examples Of "Swordfish" Piercing Wooden Ships, Harry L. Fierstine, Oliver Crimmen

Biological Sciences

No abstract provided.


Use Of Rostral Characters For Identifying Adult Billfishes (Teleostei: Perciformes: Istiophoridae And Xiphiidae), Harry L. Fierstine, Nicole L. Voigt Feb 1996

Use Of Rostral Characters For Identifying Adult Billfishes (Teleostei: Perciformes: Istiophoridae And Xiphiidae), Harry L. Fierstine, Nicole L. Voigt

Biological Sciences

Seven species of the family Istiophoridae and Xiphias gladiu6 were identified using only features of their rostrum. In the Istiophoridae, two rostral regions were emphasized, one-fourth and one·half the distance between the distal tip and the orbital margin of the lateral ethmoid bone. Characters studied in each region were the depth and width of rostrum and height, width, and position of nutrient canals (as seen in cross-section). Characters studied without reference to region were the distribution of denticles on both dorsal and ventral surfaces of the bilI and position of the prenasal bone. In the Xiphiidae, the only characters studied …


Trade-Offs In Parasitology, Evolution And Behavior, Marlene Zuk, M. J. Bryant, Gita R. Kolluru, V. Mirmovitch Feb 1996

Trade-Offs In Parasitology, Evolution And Behavior, Marlene Zuk, M. J. Bryant, Gita R. Kolluru, V. Mirmovitch

Biological Sciences

No abstract provided.


Light-Saturated Primary Production In Antarctic Coastal Waters, Mark A. Moline, Barbara B. Prezelin, Herve Claustre Jan 1996

Light-Saturated Primary Production In Antarctic Coastal Waters, Mark A. Moline, Barbara B. Prezelin, Herve Claustre

Biological Sciences

No abstract provided.


Temporal Dynamics Of Coastal Antarctic Phytoplankton: Environmental Driving Forces And Impact Of 1991/92 Summer Diatom Bloom On The Nutrient Regimes, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield, Raymond C. Smith Jan 1996

Temporal Dynamics Of Coastal Antarctic Phytoplankton: Environmental Driving Forces And Impact Of 1991/92 Summer Diatom Bloom On The Nutrient Regimes, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield, Raymond C. Smith

Biological Sciences

Within the Palmer Long Term Ecological Research Program (PAL-LTER), a suite of environmental data sets were collected at a nearshore station throughout the 1991/92 austral summer. Seasonal changes are presented in the context of phytoplankton community ecology. Subseasonal fluctuations in sea-ice coverage, freshwater inputs, as well as wind driven and advective processes disrupting stratified surface waters, appeared to be the major driving forces affecting the timing, duration and demise of local phytoplankton blooms. During a large diatom-dominated bloom (~30 mg chl a m-3), macronutrients were depleted to detection limits (NO3--3, PO4-3< 0.03 mmol m-3) …


Effect Of Larval Swimming Duration On Success Of Metamorphosis And Size Of The Ancestrular Lophophore In Bugula Neritina (Bryozoa), Dean E. Wendt Jan 1996

Effect Of Larval Swimming Duration On Success Of Metamorphosis And Size Of The Ancestrular Lophophore In Bugula Neritina (Bryozoa), Dean E. Wendt

Biological Sciences

There is a growing realization that events during one portion of an organism's life cycle can have both subtle and dramatic effects on other stages in the life history. Lethal and sublethal effects associated with the duration of larval swimming in marine invertebrates were examined for the bryozoan Bugula neritina. Larvae were kept swimming up to a maximum of 28 h at 20{deg}C by exposure to continuous bright fluorescent illumination. At 4-h intervals, samples of 20-40 larvae were removed from bright illumination and were exposed to seawater containing 10 mM excess KCI, an inducer of metamorphosis in this species. …


Analysing Ancient Dna, Raúl J. Cano Jan 1996

Analysing Ancient Dna, Raúl J. Cano

Biological Sciences

Much of what we know about extinct organisms comes from traits that are not preserved in the fossil record. Until recently, morphological analysis was the only tool available for scientists to determine relationships for extinct fossil organisms. We now know that ‘ancient’ DNA can be preserved in the remains of extinct organisms. By targeting specific gene sequences, it may be possible to deduce biochemical characteristics and through sequence comparisons, to estimate the extent of evolutionary divergence. By comparing the amount and type of these changes, one could estimate how quickly some DNA ‘evolves’ relative to other segments, or which genes …


Pseudomonas Aeruginosa Strain Ma01 Aerobically Metabolizes The Aminodinitrotoluenes Produced By 2,4,6-Trinitrotoluene Nitro Group Reduction, Mark A. Alvarez, Christopher Kitts, James L. Botsford, Pat J. Unkefer Nov 1995

Pseudomonas Aeruginosa Strain Ma01 Aerobically Metabolizes The Aminodinitrotoluenes Produced By 2,4,6-Trinitrotoluene Nitro Group Reduction, Mark A. Alvarez, Christopher Kitts, James L. Botsford, Pat J. Unkefer

Biological Sciences

Many microbes reduce the nitro substituents of 2,4,6-trinitrotoluene (TNT), producing aminodinitrotoluenes (ADNTs). These compounds are recalcitrant to further breakdown and are acutely toxic. In a search for organisms capable of metabolizing ADNTs, a bacterial strain was isolated for the ability to use 2-aminobenzoate (anthranilate) as sole C-source. This isolate, Pseudomonas aeruginosa MAO1, metabolized TNT by first reducing one nitro group to form either 2-amino-4,6-dinitrotoluene (2ADNT) or 4 -amino-2,6-dinitrotoluene(4ADNT). However, strain MA01 was distinct from other TNT-reducing organisms in that it transformed these compounds into highly polar metabolites through an 02-dependent process. Strain MAOl was able to cometabolize TNT, 2ADNT, and …


On The Dangers Of Interpopulational Transfers Of Monarch Butterflies, Lincoln P. Brower, Linda S. Fink, Andrew Van Zandt Brower, Kingston L. H. Leong, Karen Oberhauser, Sonia Altizer, Orley Taylor, Daniel Vickerman, William H. Calvert, Tonya Van Hook, Alfonso Alonso-Mejia, Stephen B. Malcolm, Denis F. Owen, Myron P. Zalucki Sep 1995

On The Dangers Of Interpopulational Transfers Of Monarch Butterflies, Lincoln P. Brower, Linda S. Fink, Andrew Van Zandt Brower, Kingston L. H. Leong, Karen Oberhauser, Sonia Altizer, Orley Taylor, Daniel Vickerman, William H. Calvert, Tonya Van Hook, Alfonso Alonso-Mejia, Stephen B. Malcolm, Denis F. Owen, Myron P. Zalucki

Biological Sciences

No abstract provided.


Reply To Nylin, Wickman & Wiklund Regarding Sex Ratios Of California Overwintering Monarch Butterflies, Dennis F. Frey, Kingston L. H. Leong Feb 1995

Reply To Nylin, Wickman & Wiklund Regarding Sex Ratios Of California Overwintering Monarch Butterflies, Dennis F. Frey, Kingston L. H. Leong

Biological Sciences

No abstract provided.


Statistical Analyses Of Environmental Predictors For Phytoplankton Photosynthetic Parameters And Productivity In An Antarctic Time Series Database, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield Jan 1995

Statistical Analyses Of Environmental Predictors For Phytoplankton Photosynthetic Parameters And Productivity In An Antarctic Time Series Database, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield

Biological Sciences

No abstract provided.


Palmer Lter: Photoacclimation In A Coastal Phytoplankton Bloom, Oscar Schofield, Mark A. Moline, Barbara B. Prezelin Jan 1995

Palmer Lter: Photoacclimation In A Coastal Phytoplankton Bloom, Oscar Schofield, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

No abstract provided.


Induction Of Larval Settlement By Kcl In Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott Jan 1995

Induction Of Larval Settlement By Kcl In Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott

Biological Sciences

Elevation of the K+ concentration in seawater (added as KCl) induces larval settlement and metamorphosis in Bugula simplex, B. stolonifera, and B. turrita. All three of these bryozoan species have similar bell-shaped dose-response curves: 5 mM excess K+ is sufficient to increase settlement and metamorphosis significantly over seawater controls in all the species and optimal responses to excess K concentrations occur ations at 10-25 mM, 5-10 mM, and 10-15 mM for B. simplex, B. stolonifera, and B. turrita, respectively. Percent settlement in all three species is decreased at levels greater than 25 mniM excess …


Isolation Of Three Hexahydro-1,3,5-Trinitro-1,3,5-Triazine- Degrading Species Of The Family Enterobacteriaceae From Nitramine Explosive-Contaminated Soil, Christopher Kitts, Daryl P. Cunningham, Pat J. Unkefer Dec 1994

Isolation Of Three Hexahydro-1,3,5-Trinitro-1,3,5-Triazine- Degrading Species Of The Family Enterobacteriaceae From Nitramine Explosive-Contaminated Soil, Christopher Kitts, Daryl P. Cunningham, Pat J. Unkefer

Biological Sciences

Three species of the family Enterobacteriaceae that biochemically reduced hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were isolated from nitramine explosive-contaminated soil. Two isolates, identified as Morganella morganii and Providencia rettgeri, completely transformed both RDX and the nitroso-RDX reduction intermediates. The third isolate, identified as Citrobacter freundii, partially transformed RDX and generated high concentrations of nitroso-RDX intermediates. All three isolates produced 14CO2 from labeled RDX under O2-depleted culture conditions. While all three isolates transformed HMX, only M. morganii transformed HMX in the presence of RDX.


Review Of Survival, Reproduction, And Behavior By J.R. Krebs And N.B. Davies, Marlene Zuk, Torgeir S. Johnsen, Gita R. Kolluru, Kurt A. Mckean, Bradd Schulke Sep 1994

Review Of Survival, Reproduction, And Behavior By J.R. Krebs And N.B. Davies, Marlene Zuk, Torgeir S. Johnsen, Gita R. Kolluru, Kurt A. Mckean, Bradd Schulke

Biological Sciences

No abstract provided.


The Role Of Enzyme Activation State In Limiting Carbon Assimilation Under Variable Light Conditions, Gretchen F. Sassenrath-Cole, Robert W. Pearcy, Scott J. Steinmaus Aug 1994

The Role Of Enzyme Activation State In Limiting Carbon Assimilation Under Variable Light Conditions, Gretchen F. Sassenrath-Cole, Robert W. Pearcy, Scott J. Steinmaus

Biological Sciences

The mechanisms regulating transient photosynthesis by soybean (Glycine max) leaves were examined by comparing photosynthetic rates and carbon reduction cycle enzyme activities under flashing (saturating 1 s lightflecks separated by low photon flux density (PFD) periods of different durations) and continuous PFD. At the same mean PFD, the mean photosynthetic rates were reduced under flashing as compared to continuous light. However, as the duration of the low PFD period lengthened, the CO2 assimilation attributable to a lightfleck increased. This enhanced lightfleck CO2 assimilation was accounted for by a greater postillumination CO2 fixation occurring after the …


Disparate Rates Of Molecular Evolution In Cospeciating Hosts And Parasites, M. S. Hafner, P. D. Sudman, F. X. Villablanca, T. A. Spradling, J. W. Demastes, S. A. Nadler Aug 1994

Disparate Rates Of Molecular Evolution In Cospeciating Hosts And Parasites, M. S. Hafner, P. D. Sudman, F. X. Villablanca, T. A. Spradling, J. W. Demastes, S. A. Nadler

Biological Sciences

DNA sequences for the gene encoding mitochondrial cytochrome oxidase I in a group of rodents (pocket gophers) and their ectoparasites (chewing lice) provide evidence for cospeciation and reveal different rates of molecular evolution in the hosts and their parasites. The overall rate of nucleotide substitution (both silent and replacement changes) is approximately three times higher in lice, and the rate of synonymous substitution (based on analysis of fourfold degenerate sites) is approximately an order of magnitude greater in lice. The difference in synonymous substitution rate between lice and gophers correlates with a difference of similar magnitude in generation times.


Azorhizobium Caulinodans Respires With At Least Four Terminal Oxidases, Christopher Kitts, Robert A. Ludwig Feb 1994

Azorhizobium Caulinodans Respires With At Least Four Terminal Oxidases, Christopher Kitts, Robert A. Ludwig

Biological Sciences

In culture, Azorhizobium caulinodans used at least four terminal oxidases, cytochrome aa3 (cytaa3), cytd, cyto, and a second a-type cytochrome, which together mediated general, respiratory electron (e-) transport to O2. To genetically dissect physiological roles for these various terminal oxidases, corresponding Azorhizobium apocytochrome genes were cloned, and three cytaa3 mutants, a cytd mutant, and a cytaa3, cytd double mutant were constructed by reverse genetics. These cytochrome oxidase mutants were tested for growth, oxidase activities, and N2 fixation properties both …


Impalement Of Marine Turtles (Reptilia, Chelonia: Cheloniidae And Dermochelyidae) By Billfishes (Osteichthyes, Perciformes: Istiophoridae And Xiphiidae), John G. Frazier, Harry L. Fierstine, Sallie C. Beavers, Federico Achaval, Hiroyuki Suganuma, Robert L. Pitman, Yuichiro Yamaguchi, Carlos Ma. Prigioni Jan 1994

Impalement Of Marine Turtles (Reptilia, Chelonia: Cheloniidae And Dermochelyidae) By Billfishes (Osteichthyes, Perciformes: Istiophoridae And Xiphiidae), John G. Frazier, Harry L. Fierstine, Sallie C. Beavers, Federico Achaval, Hiroyuki Suganuma, Robert L. Pitman, Yuichiro Yamaguchi, Carlos Ma. Prigioni

Biological Sciences

Billfishes have long been known to impale a great variety of objects, but there are only two brief, obscure records of marine turtles being speared. Details are presented on these two, as well as on two other confirmed records; data from two additional unconfirmed records are also presented. In total, three species of marine turtles are known to have been impaled by three species of billfishes; a fourth species of fish and a fourth species turtle are listed in an unconfirmed case. Records come from the eastern and western Pacific as well as the eastern Atlantic. Of the four confirmed …


Icecolors '93: Biological Weighting Function For The Ultraviolet Inhibition Of Carbon Fixation In A Natural Antarctic Phytoplankton Community, Nicholas Boucher, Barbara B. Prezelin, T. Evens, R. Jovine, B. Kroon, Mark A. Moline, Oscar Schofield Jan 1994

Icecolors '93: Biological Weighting Function For The Ultraviolet Inhibition Of Carbon Fixation In A Natural Antarctic Phytoplankton Community, Nicholas Boucher, Barbara B. Prezelin, T. Evens, R. Jovine, B. Kroon, Mark A. Moline, Oscar Schofield

Biological Sciences

No abstract provided.


Palmer Lter: Impact Of A Large Diatom Bloom On Macronutrient Distribution In Arthur Harbor During Austral Summer 1991-1992, Mark A. Moline, Barbara B. Prezelin Jan 1994

Palmer Lter: Impact Of A Large Diatom Bloom On Macronutrient Distribution In Arthur Harbor During Austral Summer 1991-1992, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

No abstract provided.


Palmer Lter: Photoadaptation In A Coastal Phytoplankton Bloom And Impact On The Radiation Utilization Efficiency For Carbon Fixation, Oscar Schofield, Barbara B. Prezelin, Mark A. Moline Jan 1994

Palmer Lter: Photoadaptation In A Coastal Phytoplankton Bloom And Impact On The Radiation Utilization Efficiency For Carbon Fixation, Oscar Schofield, Barbara B. Prezelin, Mark A. Moline

Biological Sciences

No abstract provided.


Spatial And Temporal Aspects Of Populations Revealed By Mitochondrial Dna, Francis X. Villablanca Jan 1994

Spatial And Temporal Aspects Of Populations Revealed By Mitochondrial Dna, Francis X. Villablanca

Biological Sciences

The evolutionary analysis of DNA sequences bridges phylogenetics and population genetics. Ancient DNA (aDNA) alJows the study of extinct genotypes, populations, and species, as well as dichronic comparisons of extant populations and species. Thus a DNA forges an empirical link between history and two inherently historical fields of research. Fortunately, the conceptual frameworks of phylogenetics and population genetics can easily be extended to encompass advances being made in the study of aDNA.


Can Microhabitat Selection Or Differences In 'Catchability' Explain Male-Biased Sex Ratios In Overwintering Populations Of Monarch Butterflies?, Dennis F. Frey, Kingston L.H. Leong May 1993

Can Microhabitat Selection Or Differences In 'Catchability' Explain Male-Biased Sex Ratios In Overwintering Populations Of Monarch Butterflies?, Dennis F. Frey, Kingston L.H. Leong

Biological Sciences

No abstract provided.