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Articles 2611 - 2640 of 2749

Full-Text Articles in Biology

Synthesis Of Nitrosyl Metallpoprphyrins, Thomas M. Braxton Jr. May 1995

Synthesis Of Nitrosyl Metallpoprphyrins, Thomas M. Braxton Jr.

McCabe Thesis Collection

Nitric oxide, NO, is a molecule with great versatility and importance. Made up of only a single atom of nitrogen and a single atom of oxygen, nitric oxide is perhaps one of the smallest paramagnetic molecules found in nature. The functions of NO in the body are not all known, but this molecule definitely plays a variety of roles. It is involved in the regulation of blood pressure, and it sometimes acts as a messenger for cells as well as a killer of them. It also is important in the defense of the body against foreign invaders. The significance of …


Bones Of Puffinus Lherminieri Lesson (Aves: Procellaridae) And Two Other Vertebrates From Cueva Del Agua, Mona Isalnd, Puerto Rico (West Indies), Angel M. Nieves-Rivera, John M. Mylroie, Donald A. Mcfarlane Jan 1995

Bones Of Puffinus Lherminieri Lesson (Aves: Procellaridae) And Two Other Vertebrates From Cueva Del Agua, Mona Isalnd, Puerto Rico (West Indies), Angel M. Nieves-Rivera, John M. Mylroie, Donald A. Mcfarlane

WM Keck Science Faculty Papers

From a dive in Cueva del Agua, Mona Island, Puerto Rico, twelve un-mineralized bones of Puffinus Lherminieri Lesson, one of Cyclura stejnegeri Stejneger, and one of Moormops blainvilii Leach were collected. The subfossil evidence confirms that P. Lherminieri was a common species on Mona Island. Cyclura stejnegeri and M. blainvilii probably became trapped and died in the pool chamber.


The Effects Of Nutrient Loading On Plant And Algae Population: A Comparison Study Of East Gemini Lake And Lower Stumpf Lake, Nick Leonard Jan 1995

The Effects Of Nutrient Loading On Plant And Algae Population: A Comparison Study Of East Gemini Lake And Lower Stumpf Lake, Nick Leonard

Honors Theses, 1963-2015

Eutrophication of lakes has become an increasing problem for many bodies of water. By analyzing the nutrients available and the phytoplankton and macrophyte populations, evaluation and differentiation of East Gemini Lake and Stumpf Lake were made concerning their trophic state. This determination allowed for the further understanding of the effect the trophic state has on the flora of an aquatic system. It was determined that East Gemini Lake was eutrophic based on its available nutrients and phytoplankton populations. In contrast, Stumpf Lake was determined to be mesotrophic having lower available nutrients and less phytoplankton population density with fewer major phytoplnakton …


How Amaranth Grain Affects Total Body Weight And Major Organ Weight In The Mongolian Gerbil, Rhoshonda Montgomery- Conway May 1994

How Amaranth Grain Affects Total Body Weight And Major Organ Weight In The Mongolian Gerbil, Rhoshonda Montgomery- Conway

McCabe Thesis Collection

Purpose and Objectives

The purpose of this research is to determine effects of amaranth grain of the body weight and organ weight of the Mongolian gerbil. The literature research indicates that amaranth results in physiological changes that appear to be species-specific rather than general. Since the gerbil is a granivorous animal, it is hypothesized that amaranth will be completely digested and that its nutritional quality will maintain normal to increased growth. While the results of this study cannot be applied to other animals, information has been gained with regard to the influence of amaranth grain on the Mongolian gerbil.


Study Of Existing Information Concerning Water Quality Within Lake Mead, Vicki Scharnhorst, Southern Nevada Water Authority Feb 1994

Study Of Existing Information Concerning Water Quality Within Lake Mead, Vicki Scharnhorst, Southern Nevada Water Authority

Publications (WR)

The purpose of Task 010A15M of the Southern Nevada Water Authority (SNWA) Treatment and Transmission Facility (TTF) contract is to conduct a study of existing information concerning water quality within Lake Mead and identify additional water quality studies that are needed to supplement existing data. The objective of this task is not to discuss treatability of the raw water source; this is addressed by Task 010A18M, "Define Water Treatment Requirements." In addition, a narrative on the effect of pending Safe Drinking Water Act amendments and a determination of treated water quality goals is included in Task 010A16M, "Review Safe Drinking …


Comparison Of Dietary Overlap Between Allopatric And Sympatric Geckos, Paul D. Klawinski, R. Kathryn Vaughan, Daniel Saenz, William Godwin Jan 1994

Comparison Of Dietary Overlap Between Allopatric And Sympatric Geckos, Paul D. Klawinski, R. Kathryn Vaughan, Daniel Saenz, William Godwin

Faculty Publications

Two gecko species, Hemidactylus turcicus and Cyrtopodion scabrum, have been introduced into the Port of Galveston, Texas. While H. turcicus has been established for a longer period of time, the relatively recent introduction of C. scabrum near the entrance of the Port has apparently led to the displacement of H. turcicus in that area. This has resulted in a distribution in which the two populations’ are largely allopatric except for a narrow band of sympatry at the periphery of each of their ranges. We examined stomach contents of both species in allopatry and sympatry in order to determine if …


Ua3/8/1 L.Y. Lancaster Professorship Report, Wku Ogden College Of Science & Technology Jan 1994

Ua3/8/1 L.Y. Lancaster Professorship Report, Wku Ogden College Of Science & Technology

WKU Administration Documents

Report of activities by Dr. Blaine Ferrell, L.Y. Lancaster Professor for the year 1993-94, funded by Ogden Foundation.


Identification Of Tire Leachate Toxicants And A Risk Assessment Of Water Quality Effects Using Tire Reefs In Canals, S. M. Nelson, G. Mueller, D. C. Hemphill, U.S. Bureau Of Reclamation Jan 1994

Identification Of Tire Leachate Toxicants And A Risk Assessment Of Water Quality Effects Using Tire Reefs In Canals, S. M. Nelson, G. Mueller, D. C. Hemphill, U.S. Bureau Of Reclamation

Publications (WR)

Cover is an important component of aquatic habitat and fisheries management. Fisheries biologists often try to improve habitats through the addition of natural and artificial material to improve cover diversity and complexity. Habitat-improvement programs range from submerging used Christmas trees to more complex programs using sophisticated artificial habitat modules. Used automobile tires have been employed in the large scale construction of reefs and fish attractors in marine environments and to a lesser extent in freshwater and have been recognized as a durable, inexpensive and long-lasting material which benefits fishery communities.

Recent studies by the U.S. Bureau of Reclamation have quantified …


Considerations For Evaluating Ultraviolet Radiation-Induced Genetic Damage Relative To Antarctic Ozone Depletion, Deneb Karentz Jan 1994

Considerations For Evaluating Ultraviolet Radiation-Induced Genetic Damage Relative To Antarctic Ozone Depletion, Deneb Karentz

Biology Faculty Publications

Springtime ozone depletion over the Antarctic results in increased UVB in local marine environments. It has been established that decreases in primary productivity occur with decreases in ozone concentrations, but the impact of increased UVB on the functioning and stability of the ecosystem has not yet been determined. Very little has been done to evaluate the potential for genetic damage caused by the increase in UVB, and this type of damage is most significant relative to the fitness and maintenance of populations. An essential problem in evaluating genotoxic effects is the lack of appropriate techniques to sample and quantify genetic …


Modeling Daily Production Of Aquatic Macrophytes From Irradiance Measurements: A Comparative Analysis, Richard C. Zimmerman, Alejandro C. Pasini, Randall S. Alberte Jan 1994

Modeling Daily Production Of Aquatic Macrophytes From Irradiance Measurements: A Comparative Analysis, Richard C. Zimmerman, Alejandro C. Pasini, Randall S. Alberte

OES Faculty Publications

The importance of submerged aquatic macrophytes to coastal ecosystems has generated a need for knowledge of minimum light levels that will support the maintenance and restoration of healthy populations. Our goals were (1) to evaluate the sensitivity to natural, non-sinusoidal fluctuations in irradiance I of analytical integration techniques for calculating daily carbon gain, (2) to evaluate the Hsat (the daily period of I-saturated photosynthesis) model of daily production relative to models based on instantaneous photosynthesis vs irradiance (P vs I) and (3) to provide some guidance for the temporal density of irradiance data required for accurate estimation of …


Body Size In Amblyrhiza Inundata (Rodentia, Caviomorpha), An Extinct Megafaunal Rodent From The Anguilla Bank, West Indies: Estimates And Implications, Audrone R. Biknevicius, Donald A. Mcfarlane, Ross D. E. Macphee Nov 1993

Body Size In Amblyrhiza Inundata (Rodentia, Caviomorpha), An Extinct Megafaunal Rodent From The Anguilla Bank, West Indies: Estimates And Implications, Audrone R. Biknevicius, Donald A. Mcfarlane, Ross D. E. Macphee

WM Keck Science Faculty Papers

Rodent species typically evolve larger mean body sizes when isolated on islands, but the extinct caviomorph Amblyrhiza inundata, known only from Quaternary cave deposits on the islands of Anguilla and St. Martin (northern Lesser Antilles), provides an unusually dramatic example of insular gigantism. Here we report on a series of body mass estimates for Amblyrhiza using predictive equations based on anteroposterior diameters and cortical cross-sectional areas of humeral and femoral diaphyses. Analyses of 14 isolated specimens (5 femoral, 9 humeral), all representing adult or near adult animals, yield body mass estimates ranging from slightly less than 50 kg to more …


A Comparison Of No And N20 Production By The Autophic Nitrifier Nitrosomonas Europaea And The Heterotrophic Nitrifier Alcaligenes Faecalis, Iris C. Anderson, Mark Poth, Julie Homstead, David J. Burdige Nov 1993

A Comparison Of No And N20 Production By The Autophic Nitrifier Nitrosomonas Europaea And The Heterotrophic Nitrifier Alcaligenes Faecalis, Iris C. Anderson, Mark Poth, Julie Homstead, David J. Burdige

OES Faculty Publications

Soil microorganisms are important sources of the nitrogen trace gases NO and N2O for the atmosphere. Present evidence suggests that autotrophic nitrifiers such as Nitrosomonas europaea are the primary producers of NO and N2O in aerobic soils, whereas denitrifiers such as Pseudomonas spp. or Alcaligenes spp. are responsible for most of the NO and N2O emissions from anaerobic soils. It has been shown that Alcaligenes faecalis, a bacterium common in both soil and water, is capable of concomitant heterotrophic nitrification and denitrification. This study was undertaken to determine whether heterotrophic nitrification might be …


Geological Field Guide To The Cedar Point Biological Station, Keith County, Nebraska, Robert F. Diffendal Jr., Roger K. Pabian Feb 1993

Geological Field Guide To The Cedar Point Biological Station, Keith County, Nebraska, Robert F. Diffendal Jr., Roger K. Pabian

School of Natural Resources: Faculty Publications

This field guide was produced by staff members of the Conservation and Survey Division of the University of Nebraska originally in 1979 at the request of Dr. Brent Nickol, former Director of the Cedar Point Biological Station. It is an introduction to the geologic history and paleoecology of the Cedar Point area intended for students, staff, and other persons using the camp. This revision has been made some 15 years after the first version to reflect changes in ideas resulting from new data collected during that time.

Users of this guide should take care when studying the rock exposures described …


Amblyrhiza And The Vertebrate Paleontology Of Anguillean Caves, Donald A. Mcfarlane, Ross D. E. Macphee Jan 1993

Amblyrhiza And The Vertebrate Paleontology Of Anguillean Caves, Donald A. Mcfarlane, Ross D. E. Macphee

WM Keck Science Faculty Papers

Recorded interest in the caves of Anguilla dates back to the second half of the nineteenth century. The earliest explorations were concerned with the locating phosphatic cave earths, and resulted in the mining of several sites. Incidental to this work, the bones of the largest island rodent ever discovered were collected from Aguillan caves. Whereas the phosphate mining operations were short-lived, the remains of the giant rodent Amblyrhiza have catalyzed a continued interest in the caves of Anguilla. The most recent series of explorations have provided the first adequate documentation of Amhlyrhiza fossil sites, and have started to yield radiometric …


A Review Of The Biology Of Giant Salvinia, J. Douglas Oliver Jan 1993

A Review Of The Biology Of Giant Salvinia, J. Douglas Oliver

Faculty Publications and Presentations

Giant salvinia (Salviniaceae) is a potentially serious aquatic weed that is native to Brazil. It has been reported in more than 20 countries, but is not established in the U.S. at this time. Mitchell and Tur (1975) reported that three years after the formation of the Kariba Reservoir in Africa, giant salvinia blanketed 21.5% or 1003 km2 of the reservoir surface area. Creagh (199111992) wrote, "A single small plant may grow to form a thick mat covering more than 100 sq. km. in just three months - choking lakes and waterways, reducing populations of aquatic plants and animals and in …


Phytoplankton Relationships To Water Quality In Lake Drummond And Two Drainage Ditches, Christine G. Phillips, Harold G. Marshall Jan 1993

Phytoplankton Relationships To Water Quality In Lake Drummond And Two Drainage Ditches, Christine G. Phillips, Harold G. Marshall

Biological Sciences Faculty Publications

A twelve-month phytoplankton study was conducted in Lake Drummond and Washington and Jericho Ditches from December 1988 to November 1989. Four dominant phytoplankton groups were identified at these sites. These were the Bacillariophyceae, Cyanophyceae, Cryptophyceae and an autotrophic picoplankton component. Over the past 20 years there has been a decrease in the mean pH levels of Lake Drummond and the replacement of one its former major components, the Chlorophyceae, by the Cyanophyceae. Based on water quality analysis results and species diversity indices, Lake Drummond is classified as in an early eutrophic stage of development.


Southern Nevada Effluent Wetlands: A Proposed Cooperative Venture Between The Bureau Of Reclamation & City Of Las Vegas, Bureau Of Reclamation Nov 1992

Southern Nevada Effluent Wetlands: A Proposed Cooperative Venture Between The Bureau Of Reclamation & City Of Las Vegas, Bureau Of Reclamation

Publications (WR)

Throughout North America there is a growing interest in constructed wetlands, both as relatively inexpensive, low-maintenance systems for removing nutrients from wastewater, and as a means of using municipal wastewater to enhance wildlife habitat and create public use opportunities. Because wetlands appear to have good potential as a component in the overall management of scarce water resources, the Bureau of Reclamation (Reclamation) has undertaken several cooperative research and demonstration projects to evaluate their effectiveness in a variety of local environments. While a number of projects have demonstrated that wetlands can be beneficially employed to improve water quality, few such projects …


Evidence For Helical Structures In Poly(1-Olefin Sulfones) By Transmission Electron Microscopy, George C. Ruben, W H. Stockmayer May 1992

Evidence For Helical Structures In Poly(1-Olefin Sulfones) By Transmission Electron Microscopy, George C. Ruben, W H. Stockmayer

Dartmouth Scholarship

Transmission electron microscope images were obtained of fractions of poly(1-tetradecene sulfone) and poly(cyclohexene sulfone) cast from very dilute solutions (0.007%, wt/vol) and rapidly freeze-dried on a mica surface. The samples were then vertically platinum-carbon (Pt-C) replicated with 9 +/- 0.3-A Pt-C and held together with 128 A of electron-transparent evaporated carbon. The Pt-C coating enlarges the molecular chain diameters by approximately 5 A, so that a single polysulfone chain has an apparent diameter of 9-12 A in the transmission electron microscope. Poly(1-tetradecene sulfone) forms short helical regions that show irregular helical turns of pitch 7-18 A, two to eight turns …


Thermal Properties Of Some Lipid Components Of Cell Membranes, Lihua Wei Apr 1992

Thermal Properties Of Some Lipid Components Of Cell Membranes, Lihua Wei

Masters Theses & Specialist Projects

Phospholipids are the major structural components of the lipid portion of biological membranes. The study of the thermal properties of these phospholipid provides a systematic understanding of the relationships between the chemical structures and functional properties of phospholipid molecules in artificial and biological membranes. This study examined the thermal behavior of phospholipids in the solid state using DSC and TG coupled with FITR. The phospholipids were found to have phase transitions below the melting point. Egg-yolk lecithin had four transitions below its melting point; sphingomyelin had two phase transitions below its melting point. Phosphatidylethanolamine and phosphatidylserine had complex phase transitions. …


Nitrogen And Carbon Isotope Studies Of A Bat Guano Core From Eagle Creek Cave, Arizona, Usa, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya Feb 1992

Nitrogen And Carbon Isotope Studies Of A Bat Guano Core From Eagle Creek Cave, Arizona, Usa, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya

WM Keck Science Faculty Papers

Nitrogen and carbon isotope ratios were studied in a stratified deposit of guano of Mexican Free-tailed bats in Eagle Creek Cave, Arizona, U.S.A. Little diagenetic change was observed over the 25-year time span of the guano deposit. High aridity and reduced circulation of air in the cave are hypothesized to have slowed the normally rapid decomposition of the excreta and the subsequent escape of resultant ammonia. The results suggest the high dependency of the speed of diagenetic change on specific physical and other conditions of the caves and indicate that great care need be exercised in the interpretation of the …


Carbon And Nitrogen Isotopic Signatures Of Bat Guanos As A Record Of Past Environments, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya Feb 1992

Carbon And Nitrogen Isotopic Signatures Of Bat Guanos As A Record Of Past Environments, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya

WM Keck Science Faculty Papers

Carbon and nitrogen isotope ratios were measured for various ecogeochemical samples relevant to bat guano ecosystems. In particular, ca. 800-year-old subfossil guano from Jackson's Bay Cave Compex, Jamaica, yielded ratios similar to the modern guano from other Jamaican bat caves but quite different from modern guano of the same area. Diagenetic change and differences in bat food habits were unlikely explanations for the observation. Instead, insects that feed on C4 and CAM plants were the main prey for the bats in present Jackson's Bay area, while the ultimate source of organic matter for bats in other Jamaican caves and for …


Partial Characterization Of The Major Lipooligosaccharide From A Strain Of Haemophilus Ducreyi, The Causative Agent Of Chancroid, A Genital Ulcer Disease, William Melaugh, Nancy J. Phillips, A A. Campagnari, R Karalus, B W. Gibson Jan 1992

Partial Characterization Of The Major Lipooligosaccharide From A Strain Of Haemophilus Ducreyi, The Causative Agent Of Chancroid, A Genital Ulcer Disease, William Melaugh, Nancy J. Phillips, A A. Campagnari, R Karalus, B W. Gibson

Chemistry Faculty Publications

The first preliminary structure of a surface lipooligosaccharide from Haemophilus ducreyi has been determined. The major oligosaccharide was released by mild acid hydrolysis and analyzed by liquid secondary ion and tandem mass spectrometry. The mass spectral data combined with composition and methylation analysis yielded the most probable structure; Gal1----4GlcNAc1----3Gal1----4Hep1----6Glc1----( Hep1----2Hep1----)3,4Hep1---- KDO, where the reducing terminal 3-deoxy-D-manno-octulosonic acid (or KDO) exists in an anhydro form. This anhydro species results from the elimination of a phosphate from C-4 of KDO during mild acid hydrolysis. The core heptose trisaccharide consists of L-glycero-D-manno-heptose, but analysis of the peracetylated sugars indicated that the 1,4-linked heptose …


Ua3/8/1 L.Y. Lancaster Professorship Report, Wku Ogden College Of Science & Technology Jan 1992

Ua3/8/1 L.Y. Lancaster Professorship Report, Wku Ogden College Of Science & Technology

WKU Administration Documents

Report by Dr. Blaine Ferrell, L.Y. Lancaster Professor about activities for 1991-1992 funded by the Ogden Foundation.


Consumption Rates, Evacuation Rates And Diets Of Pygmy Killifish, Leptolucania Ommata, And Mosquitofish, Gambusia Affinis In The Okefenokee Swamp, J. Douglas Oliver Dec 1991

Consumption Rates, Evacuation Rates And Diets Of Pygmy Killifish, Leptolucania Ommata, And Mosquitofish, Gambusia Affinis In The Okefenokee Swamp, J. Douglas Oliver

Faculty Publications and Presentations

I studied feeding dynamics of Leptolucania ommata and Gambusia affinis in the Okefenokee Swamp. Both fishes mainly ate insect larvae (such as Chironomidae) and Cladocera. Evacuation rates ranged from 0.143 (L. ommala in winter) to 0.279/hour (L. ommala in summer). Daily food consumption (dry weight) ranged from 24.2 (L. ommata in winter) to 148.3 mg/g/day (G. affinis in summer). Maximum consumption by both species was estimated at 26.31 mg/t m2 / day, in summer. These values are consistent with other observations supporting a hypothesis that invertebrate prey production is substantial in these blackwater wetlands.


Ua3/8/1 John Robinson Professorship Report, Wku Ogden College Of Science & Technology Jun 1991

Ua3/8/1 John Robinson Professorship Report, Wku Ogden College Of Science & Technology

WKU Administration Documents

Report by Dr. John Riley, John Robinson Professor of activities for 1990-1991 funded by Ogden Foundation.


Cystic Fibrosis: Cluster Analysis Of Microbiology And Pulmonary Function, Lori Lee M. Larson '91 May 1991

Cystic Fibrosis: Cluster Analysis Of Microbiology And Pulmonary Function, Lori Lee M. Larson '91

Honors Projects

In an attempt to find a relationship between pulmonary infection and pulmonary function in cystic fibrosis (CF) patients, microbiology data and pulmonary function test (PFT) data for clinic patients' visits were obtained from the University of Minnesota Relational Database. The two files were merged, totaling 12,193 cases, and then analyzed using a quick cluster subroutine of SPSSX on the University of Illinois IBM Mainframe System. QUICK CLUSTER analysis showed a relationship between the virulence of the microorganisms, the amount of growth of the microorganisms, and the pulmonary function test scores of CF patients


Potential Impacts Of Biomass Production In The United States On Biological Diversity, James H. Cook, Jan Beyea, Kathleen H. Keeler Jan 1991

Potential Impacts Of Biomass Production In The United States On Biological Diversity, James H. Cook, Jan Beyea, Kathleen H. Keeler

School of Biological Sciences: Faculty Publications

Biomass could be a renewable source of energy and chemicals that would not add CO2 to the atmosphere. It will become economically competitive as its cost decreases relative to energy costs, and biotechnology is expected to accelerate this trend by increasing biomass productivity. Pressure to slow global warming may also make biomass more attractive. Substantial dependence on biomass would entail massive changes in land use, risking serious reductions in biodiversity through destruction of habitat for native species. Forests could be managed and harvested more intensively, and virtually all arable land unsuitable for high-value agriculture or silviculture might be used …


Littoral And Limnetic Zooplankton Communities In Lake Mead, Nevada-Arizona, Usa, Patrick J. Sollberger, Larry J. Paulson Jan 1991

Littoral And Limnetic Zooplankton Communities In Lake Mead, Nevada-Arizona, Usa, Patrick J. Sollberger, Larry J. Paulson

Publications (WR)

Zooplankton were collected from adjacent littoral and limnetic sites in Lake Mead, Nevada-Arizona, USA. Limnetic species dominated both littoral and limnetic zooplankton communities; littoral species rarely exceeded 2% of monthly total zooplankton densities. Low species richness of littoral taxa and high similarity in species composition between littoral and limnetic habitats appeared to result from uniform horizontal physical and chemical environments, due to horizontal mixing, and from the absence aquatic macrophytes. Significant differences in spatial distribution occurred in phytoplankton biomass, total zooplankton density, and fish "abundances; highest concentrations of these factors occurred nearest an inflow high in nutrients and progressively declined …


Drop-Box Technique For Quantitative Sampling Of Macrofauna And Aquatic Plants At Restored And Natural Wetlands, J. Douglas Oliver, Andrew J. Leslie, William M. Bartodziej Jan 1991

Drop-Box Technique For Quantitative Sampling Of Macrofauna And Aquatic Plants At Restored And Natural Wetlands, J. Douglas Oliver, Andrew J. Leslie, William M. Bartodziej

Faculty Publications and Presentations

No abstract provided.


Activator-Inhibitor Control Of Tissue Growth, John A. Adam Jan 1991

Activator-Inhibitor Control Of Tissue Growth, John A. Adam

Mathematics & Statistics Faculty Publications

This note develops a simple model for the competition between activator and inhibitor control mechanisms in one-dimensional tissue growth. The pedagogic usefulness of such a model is that it is easily accessible to undergraduate applied mathematicians and is suggestive of behavior known to occur in more realistic biological systems (e.g., some types of cancer). The limitations of the model are obvious and can provide a basis for discussion of the applicability of complementary levels of description in mathematical modeling.