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Estimating The Genetic Parameters Of Yield-Related 1 Traits Under Different Nitrogen Conditions In Maize, Semra Palali Delen, Gen Xu, Jenifer Velazquez-Perfecto, Jinliang Yang

Department of Agronomy and Horticulture: Faculty Publications

Understanding the genetic basis responding to nitrogen (N) fertilization in crop production is a long-standing research topic in plant breeding and genetics. Albeit years of continuous efforts, the genetic architecture parameters, such as heritability, polygenicity, and mode of selection, underlying the N responses in maize remain largely unclear. In this study, about n = 230 maize inbred lines were phenotyped under high N (HN) and low N (LN) conditions for two consecutive years to obtain six yield-related traits. Heritability analyses suggested that traits highly responsive to N treatments were less heritable. Using publicly available SNP genotypes, the genome-wide association study …

Interaction Of Quizalofop-P-Ethyl With 2,4-D Choline And/Or Glufosinate For Control Of Volunteer Corn In Corn Resistant To Aryloxyphenoxypropionates, Mandeep Singh, Vipan Kumar, Stevan Z. Knezevic, Suat Irmak, John L. Lindquist, Santosh Pitla, Amit J. Jhala

Department of Agronomy and Horticulture: Faculty Publications

Corn resistant to aryloxyphenoxypropionates (FOPs) (Enlist™ corn) enables the use of quizalofop-p-ethyl (QPE) as a selective postemergence (POST) herbicide for control of glufosinate/glyphosate-resistant corn volunteers. Growers usually mix QPE with 2,4-D choline and/or glufosinate to achieve broad-spectrum weed control in Enlist™ corn. The objectives of this study were to (1) evaluate the efficacy of QPE applied alone or mixed with 2,4-D choline and/or glufosinate for control of glufosinate/glyphosate-resistant corn volunteers in Enlist™ corn and (2) determine the impact of application time (V3 or V6 growth stage of volunteer corn) of QPE-based treatments on volunteer corn control as well as Enlist™ …

The Biggest Grower: A Youth Gardening Competition For Growing Specialty Crops And Urban Farmers, Stacy A. Adams, Terri James

Department of Agronomy and Horticulture: Faculty Publications

Youth today have tendencies for unhealthy lifestyles, being sedentary, consuming high fat diets low in fruits and vegetables, all contributing to child obesity, Type 2 diabetes, hypertension, and precedence for life-long health concerns. For rural and economically disadvantaged urban households, poor diet is directly attributed to the inaccessibility of fresh produce, affordability and understanding of preparation of various specialty crops. Through a grant from the NE Specialty Crop Block Funding Program, The Biggest Grower Competition (BGC) was developed as a summer extension education program for youth in 8^th through 12^th grade. Project goals included; provide educational materials on …

Genome-Wide Investigation Of Snrk2 Gene Family In Two Jute Species: Corchorus Olitorius And Corchorus Capsularis, Borhan Ahmed, Fakhrul Hasan, Anika Tabassum, Rasel Ahmed, Rajnee Hassan, Ruhul Amin, Mobashwer Alam

Department of Biochemistry: Faculty Publications

Background Sucrose non-fermenting-1 (SNF1)-related protein kinase 2 (SnRK2), a plant-specifc serine/threonine kinase family, is associated with metabolic responses, including abscisic acid signaling under biotic and abiotic stresses. So far, no information on a genome-wide investigation and stress-mediated expression profling of jute SnRK2 is available. Recent whole-genome sequencing of two Corchorus species prompted to identify and characterize this SnRK2 gene family.

Result We identifed seven SnRK2 genes of each of Corchorus olitorius (Co) and C. capsularis (Cc) genomes, with similar physico-molecular properties and sub-group patterns of other models and related crops. In both species, the SnRK2 gene …

Oligogalactolipid Production During Cold Challenge Is Conserved In Early Diverging Lineages, Allison C. Barnes, Jennifer L. Myers, Samantha M. Surber, Zhikai Liang, Jeffrey P. Mower, James Schnable, Rebecca Roston

Department of Biochemistry: Faculty Publications

Oligogalactolipid production is a response to severe cold in many land plant lineages. It occurs during times of membrane damage and can be reproduced in multiple species by cytosolic acidification.

Severe cold, defined as a damaging cold beyond acclimation temperatures, has unique responses, but the signaling and evolution of these responses are not well understood. Production of oligogalactolipids, which is triggered by cytosolic acidification in Arabidopsis (Arabidopsis thaliana), contributes to survival in severe cold. Here, we investigated oligogalactolipid production in species from bryophytes to angiosperms. Production of oligogalactolipids differed within each clade, suggesting multiple evolutionary origins of severe …

A Facile Strategy For The Fabrication Of Cell-Laden Porous Alginate Hydrogels Based On Two-Phase Aqueous Emulsions, Wen Xue, Donghee Lee, Yunfan Kong, Mitchell Kuss, Ying Huang, Taesung Kim, Soonkyu Chung, Andrew T. Dudley, Seung-Hyun Ro, Bin Duan

Department of Biochemistry: Faculty Publications

Porous alginate (Alg) hydrogels possess many advantages as cell carriers. However, current pore generation methods require either complex or harsh fabrication processes, toxic components, or extra purification steps, limiting the feasibility and affecting the cellular survival and function. In this study, a simple and cell-friendly approach to generate highly porous cell-laden Alg hydrogels based on two-phase aqueous emulsions is reported. The pre-gel solutions, which contain two immiscible aqueous phases of Alg and caseinate (Cas), are cross-linked by calcium ions. The porous structure of the hydrogel construct is formed by subsequently removing the Cas phase from the ion-cross-linked Alg hydrogel. Those …

Structural Basis Of Dna Binding By The Whib-Like Transcription Factor Whib3 In Mycobacterium Tuberculosis, Tao Wan, Magdaléna Horová, Vimmy Khetrapal, Shanren Li, Camden Jones, Andrew Schacht, Xinghui Sun, Limei Zhang

Department of Biochemistry: Faculty Publications

Mycobacterium tuberculosis (Mtb) WhiB3 is an iron–sulfur cluster-containing transcription factor belonging to a subclass of the WhiB-Like (Wbl) family that is widely distributed in the phylum Actinobacteria. WhiB3 plays a crucial role in the survival and pathogenesis of Mtb. It binds to the conserved region 4 of the principal sigma factor (σ^A₄) in the RNA polymerase holoenzyme to regulate gene expression like other known Wbl proteins in Mtb. However, the structural basis of how WhiB3 coordinates with σ^A₄ to bind DNA and regulate transcription is unclear. Here we determined crystal structures …

Akkermansia Muciniphila And Its Membrane Protein Ameliorates Intestinal Inflammatory Stress And Promotes Epithelial Wound Healing Via Crebh And Mir‑143/145, Henry Wade, Kaichao Pan, Qihua Duan, Szczepan Kaluzny, Ekta Pandey, Linda Fatumoju, Viswanathan Saraswathi, Rongxue Wu, Edward N. Harris, Qiaozhu Su

Department of Biochemistry: Faculty Publications

Background The intestinal epithelial barrier is the interface for interaction between gut microbiota and host metabolic systems. Akkermansia muciniphila (A. muciniphila) is a key player in the colonic microbiota that resides in the mucus layer, whose abundance is selectively decreased in the faecal microbiota of inflammatory bowel disease (IBD) patients. This study aims to investigate the regulatory mechanism among A. muciniphila, a transcription factor cAMPresponsive element-binding protein H (CREBH), and microRNA-143/145 (miR-143/145) in intestinal inflammatory stress, gut barrier integrity and epithelial regeneration.

Methods A novel mouse model with increased colonization of A muciniphila in the intestine of CREBH knockout …

Factors Influencing Instructors’ Adoption And Continued Use Of Computing Science Technologies: A Case Study In The Context Of Cell Collective, Changsoo Song, Resa M. Helikar, Wendy M. Smith, Tomáš Helikar

Department of Biochemistry: Faculty Publications

Acquiring computational modeling and simulation skills has become ever more critical for students in life sciences courses at the secondary and tertiary levels. Many modeling and simulation tools have been created to help instructors nurture those skills in their classrooms. Understanding the factors that may motivate instructors to use such tools is crucial to improve students’ learning, especially for having authentic modeling and simulation learning experiences. This study designed and tested a decomposed technology acceptance model in which the perceived usefulness and perceived ease of use constructs are split between the teaching and learning sides of the technology to examine …

Conformal Electrodeposition Of Antimicrobial Hydrogels Formed By Self-Assembled Peptide Amphiphiles, Gervasio Zaldivar, Jiachen Feng, Leonardo Lizarraga, Yafan Yu, Luana De Campos, Kelly Mari Pires De Oliveira, Kurt Piepenbrink, Martin Conda-Sheridan, Mario Tagliazucchi

Department of Biochemistry: Faculty Publications

The colonization of biomedical surfaces by bacterial biofilms is concerning because these microorganisms display higher antimicrobial resistance in biofilms than in liquid cultures. Developing antimicrobial coatings that can be easily applied to medically-relevant complex-shaped objects, such as implants and surgical instruments, is an important and challenging research direction. This work reports the preparation of antibacterial surfaces via the electrodeposition of a conformal hydrogel of self-assembling cationic peptide-amphiphiles (PAs). Hydrogels of three PAs are electrodeposited: C₁₆K₂, C₁₆K₃, and C₁₈K₂, where C_n is an alkyl chain of n methylene …

Genetic Control Of Photoprotection And Photosystem Ii Operating Efficiency In Plants, Seema Sahay, Marcin Grzybowski, James Schnable, Katarzyna Głowacka

Department of Biochemistry: Faculty Publications

• Photoprotection against excess light via nonphotochemical quenching (NPQ) is indispensable for plant survival. However, slow NPQ relaxation under low light conditions can decrease yield of field-grown crops up to 40%.

• Using semi-high-throughput assay, we quantified the kinetics of NPQ and photosystem II operating efficiency (ΦPSII) in a replicated field trial of more than 700 maize (Zea mays) genotypes across 2 yr. Parametrized kinetics data were used to conduct genome-wide association studies.

• For six candidate genes involved in NPQ and ΦPSII kinetics in maize the loss of function alleles of orthologous genes in Arabidopsis (Arabidopsis thaliana) …

Advancements In Computational Modelling Of Biological Systems: Seventh Annual Sysmod Meeting, Bhanwar Lal Puniya, Andreas Dräger

Department of Biochemistry: Faculty Publications

The Computational Modelling of Systems Biology (SysMod) Community of Special Interest (COSI) convenes annually at the Intelligent Systems for Molecular Biology (ISMB) conference to facilitate knowledge dissemination and exchange of research findings on systems modelling from interdisciplinary domains. The SysMod meeting 2022 was held in a hybrid mode in Madison, Wisconsin, spanning a 1-day duration centred on modelling techniques, applications, and single-cell technology implementations. The meeting showcased innovative approaches to modelling biological systems using cell-specific and multiscale modelling, multiomics data integration, and novel tools to develop systems models using single-cell and multiomics technology. The meeting also recognized outstanding research by …

Impact Of Eastern Redcedar Encroachment On Water Resources In The Nebraska Sandhills, Yaser Kishawi, Aaron R. Mittelstet, Troy E. Gilmore, Dirac Twidwell, Tirthankar Roy, Nawaraj Shrestha

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Worldwide, tree or shrub dominated woodlands have encroached into herbaceous dominated grasslands. While very few studies have evaluated the impact of Eastern Redcedar (redcedar) encroachment on the water budget, none have analyzed the impact on water quality. In this study, we evaluated the impact of redcedar encroachment on the water budget in the Nebraska Sand Hills and how the decreased streamflow would increase nitrate and atrazine concentrations in the Platte River. We calibrated a Soil and Water Assessment Tool (SWAT model) for streamflow, recharge, and evapotranspiration. Using a moving window with a dilate morphological filter, encroachment scenarios of 11.9%, 16.1%, …

A Graduate-Level Field Course In Irrigation And Agricultural Water Management For An Immersive Learning Experience, Derek M. Heeren, László G. Hayde, Dean Eisenhauer, Peter G. Mccornick, Ali T. Mohammed, Aaron R. Mittelstet, Alan L. Boldt, Xin Qiao, David Mabie, Francisco Muñoz-Arriola

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Effective irrigation and agricultural water management (IAWM) is critical for food security and water security. A key requirement in designing, implementing and operation of IWM is the necessary knowledge and capacity on the farm, in the service industry and within the supply chain. Educational opportunities that not only teach the relevant principles of irrigated agriculture, but also the necessary applied skills are essential. An Irrigation Field Course was initiated by the IHE Delft Institute for Water Education (IHE Delft) and was later developed as a joint field course with IHE Delft, the University of Nebraska-Lincoln (UNL), and the Daugherty Water …

Complab V1.0: A Scalable Pore-Scale Model For Flow, Biogeochemistry, Microbial Metabolism, And Biofilm Dynamics, Heewon Jung, Hyun-Seob Song, Christof Meile

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Microbial activity and chemical reactions in porous media depend on the local conditions at the pore scale and can involve complex feedback with fluid flow and mass transport. We present a modeling framework that quantitatively accounts for the interactions between the bio(geo)chemical and physical processes and that can integrate genome-scale microbial metabolic information into a dynamically changing, spatially explicit representation of environmental conditions. The model couples a lattice Boltzmann implementation of Navier–Stokes (flow) and advection–diffusion-reaction (mass conservation) equations. Reaction formulations can include both kinetic rate expressions and flux balance analysis, thereby integrating reactive transport modeling and systems biology. We also …

Evaluating Management Zones And Crop-Sensing Relationships For Improved Irrigated Maize Nitrogen Management, Joel D. Crowther, John Parrish, Joe Luck, Richard Ferguson

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Active crop canopy sensors and management zones (MZ) are two methods of directing variable-rate, in-season nitrogen (N) fertilizer applications in maize (Zea mays L.). Researchers have suggested that integrating these two approaches may result in improved performance of sensor-based N application algorithms through increased N use efficiency and profitability. The objectives of this research study were to (1) identify soil and topographic variables that are related to in-season canopy reflectance and yield for soil-based MZ delineation and (2) determine if delineated MZ can identify areas with differential crop response to N fertilizer. N ramp blocks were placed end-to-end in field-length …

Agricultural Machinery Operator Monitoring System (Ag-Oms): A Machine Learning Approach For Real-Time Operator Safety Assessment, Terence Irumva, Herve Mwunguzi, Santosh Pitla, Bethany Lowndes, Aaron Yoder, Ka-Chun Siu

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The 2015 CS-CASH (Central States Center for Agricultural Safety and Health, 2015) Injury Surveillance Surveys showed that around 19% of injuries to agricultural producers are related to tractors or large agricultural machinery, yet only a limited number of studies are found that address tools and methods for monitoring safety behaviors of agricultural machinery operators in real-time. The current safety behavior monitoring approaches require an in-person presence, which can be both time- and cost-inefficient, and the other available methods lack a feedback element to alert operators in realtime. As a result, the research presented in this study aimed to develop an …

Crop Stress Sensing And Plant Phenotyping Systems: A Review, Geng Bai, Yufeng Ge

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Enhancing resource use efficiency in agricultural field management and breeding high-performance crop varieties are crucial approaches for securing crop yield and mitigating negative environmental impact of crop production. Crop stress sensing and plant phenotyping systems are integral to variable-rate (VR) field management and high-throughput plant phenotyping (HTPP), with both sharing similarities in hardware and data processing techniques. Crop stress sensing systems for VR field management have been studied for decades, aiming to establish more sustainable management practices. Concurrently, significant advancements in HTPP system development have provided a technological foundation for reducing conventional phenotyping costs. In this paper, we present a …

Goniometer In The Air: Enabling Brdf Measurement Of Crop Canopies Using A Cable-Suspended Plant Phenotyping Platform, Geng Bai, Yufeng Ge, Bryan Leavitt, John Gamon, David Scoby

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The Bidirectional Reflectance Distribution Function (BRDF) quantifies the distribution of the spectral reflectance of a target surface at various viewing and illumination angles. In-field measurement of the BRDF of vegetation canopies improves the characterization of offnadir measurements and informs radiative transfer models of canopy reflectance, where the Lambertian assumption does not hold. However, current field goniometers are unable to measure BRDF efficiently, especially for tall vegetation across the growing season because of the limitations of clearance, field accessibility, and flexibility of the sensor field of view. In this study, we explored the potential of using a large-scale cable-suspended field phenotyping …

Osc-Co2: Coattention And Cosegmentation Framework For Plant State Change With Multiple Features, Rubi Quiñones, Ashok Samal, Sruti Das Choudhury, Francisco Muñoz-Arriola

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Cosegmentation and coattention are extensions of traditional segmentation methods aimed at detecting a common object (or objects) in a group of images. Current cosegmentation and coattention methods are ineffective for objects, such as plants, that change their morphological state while being captured in different modalities and views. The Object State Change using Coattention-Cosegmentation (OSC-CO²) is an end-to-end unsupervised deep-learning framework that enhances traditional segmentation techniques, processing, analyzing, selecting, and combining suitable segmentation results that may contain most of our target object’s pixels, and then displaying a final segmented image. The framework leverages coattention-based convolutional neural networks (CNNs) and …

Clim4omics: A Geospatially Comprehensive Climate And Multi-Omics Database For Maize Phenotype Predictability In The United States And Canada, Parisa Sarzaeim, Francisco Muñoz-Arriola, Diego Jarquin, Hasnat Aslam, Natalia De Leon Gatti

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The performance of numerical, statistical, and data-driven diagnostic and predictive crop production modeling relies heavily on data quality for input and calibration or validation processes. This study presents a comprehensive database and the analytics used to consolidate it as a homogeneous, consistent, multidimensional genotype, phenotypic, and environmental database for maize phenotype modeling, diagnostics, and prediction. The data used are obtained from the Genomes to Fields (G2F) initiative, which provides multiyear genomic (G), environmental (E), and phenotypic (P) datasets that can be used to train and test crop growth models to understand the genotype by environment (GxE) interaction phenomenon. A particular …

Estimating Battery Size Requirements For Tractor Electrification Of Row-Crop Planting Operations, Cheetown Liew, Andrew Donesky, Mark Freyhof, Ian Tempelmeyer, Santosh Kumar Pitla

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Power sources such as batteries, used for both on-road and off-road vehicles, are advancing at a rapid pace. Electric batteries are becoming more power dense, thus allowing them to be used as a power source to replace previous diesel or gasoline-powered systems. Efforts are underway to transition off-road agricultural vehicles from Internal Combustion Engine (ICE) vehicles to electric vehicles (EVs); however, the energy requirements of typical agricultural field operations need to be fully understood before such a transition can occur. Theoretical prediction equations available in the American Society of Agricultural and Biological Engineers (ASABE) standards or the use of engine …

Viral Chemotaxis Of Paramecium Bursaria Altered By Algal Endosymbionts, Huy V.N. Ho, David Dunigan, Miranda E. Salsbery, Irina Agarkova, Zeina Al-Ameeli, James L. Van Etten, John Delong

School of Biological Sciences: Faculty Publications

Chemotaxis is widespread across many taxa and often aids resource acquisition or predator avoidance. Species interactions can modify the degree of movement facilitated by chemotaxis. In this study, we investigated the influence of symbionts on Paramecium bursaria’s chemotactic behavior toward chloroviruses. To achieve this, we performed choice experiments using chlorovirus and control candidate attractors (virus stabilization buffer and pond water). We quantified the movement of Paramecia grown with or without algal and viral symbionts toward each attractor. All Paramecia showed some chemotaxis toward viruses, but cells without algae and viruses showed the most movement toward viruses. Thus, the endosymbiotic …

Metamorphosis Imposes Variable Constraints On Genome Expansion Through Effects On Development, R. Lockridge Mueller, Clayton E. Cressler, R. S. Schwartz, R. A. Chong, M. A. Butler

School of Biological Sciences: Faculty Publications

Genome size varies ∼100,000-fold across eukaryotes and has long been hypothesized to be influenced by meta- morphosis in animals. Transposable element accumulation has been identified as a major driver of increase, but the nature of constraints limiting the size of genomes has remained unclear, even as traits such as cell size and rate of development co-vary strongly with genome size. Salamanders, which possess diverse metamorphic and non-metamorphic life histories, join the lung- fish in having the largest vertebrate genomes—3 to 40 times that of humans—as well as the largest range of variation in genome size. We tested 13 biologically-inspired hypotheses …

To What Extent Do Physiological Tolerances Determine Elevational Range Limits Of Mammals?, Jay F. Storz, Graham R. Scott

School of Biological Sciences: Faculty Publications

A key question in biology concerns the extent to which distributional range limits of species are determined by intrinsic limits of physiological tolerance. Here, we use common-garden data for wild rodents to assess whether species with higher elevational range limits typically have higher thermogenic capacities in comparison to closely related lowland species. Among South American leaf-eared mice (genus Phyllotis), mean thermogenic performance is higher in species with higher elevational range limits, but there is little among-species variation in the magnitude of plasticity in this trait. In the North American rodent genus Peromyscus, highland deermice (Peromyscus maniculatus) …

Stochasticity Directs Adaptive Evolution Toward Nonequilibrium Evolutionary Attractors, John Delong, Clayton E. Cressler

School of Biological Sciences: Faculty Publications

Stochastic processes such as genetic drift may hinder adaptation, but the effect of such stochasticity on evolution via its effect on ecological dynamics is poorly understood. Here we evaluate patterns of adaptation in a population subject to variation in demographic stochasticity. We show that stochasticity can alter population dynamics and lead to evolutionary outcomes that are not predicted by classic eco-evolutionary modeling approaches. We also show, however, that these outcomes are governed by nonequilibrium evolutionary attractors— these are maxima in lifetime reproductive success when stochasticity keeps the ecological system away from the deterministic equilibrium. These NEEAs alter the path of …

The Consumption Of Viruses Returns Energy To Food Chains, John Delong, James L. Van Etten, Zeina Al-Ameeli, Irina Agarkova, David Dunigan

School of Biological Sciences: Faculty Publications

Viruses impact host cells and have indirect effects on ecosystem processes. Plankton such as ciliates can reduce the abundance of virions in water, but whether virus consumption translates into demographic consequences for the grazers is unknown. Here, we show that small protists not only can consume viruses they also can grow and divide given only viruses to eat. Moreover, the ciliate Halteria sp. foraging on chloroviruses displays dynamics and interaction parameters that are similar to other microbial trophic interactions. These results suggest that the effect of viruses on ecosystems extends beyond (and in contrast to) the viral shunt by redirecting …

Ecological Boundaries And Constraints On Viable Eco-Evolutionary Pathways [Pre-Print], Kyle E. Coblentz, John Delong

School of Biological Sciences: Faculty Publications

Evolutionary dynamics are subject to constraints ranging from limitations on what is physically possible to limitations on the pathways that evolution can take. One set of evolutionary constraints, known as ‘demographic constraints’, constrain what can occur evolutionarily due to the population demographic or population dynamical consequences of evolution leading to conditions that make populations susceptible to extinction. These demographic constraints can limit the strength of selection or rates of environmental change populations can experience while remaining extant and the trait values a population can express. Here we further hypothesize that the population demographic and population dynamical consequences of evolution also …

Intraguild Predation Is Increased In Areas Of Low Prey Diversity In A Generalist Predator Community, Stella F Uiterwaal, Amber Squires, Bennett Grappone, Brian Dillard, Ariadne Castaneda, Sora L. Kim, John Delong

School of Biological Sciences: Faculty Publications

1. Niche differentiation and intraguild predation (IGP) can allow ecologically similar species to coexist, although it is unclear which coexistence mechanism predominates in consumer communities. Until now, a limited ability to quantify diets from metabarcoding data has precluded the use of sequencing data to determine the relative importance of these mechanisms.

2. Here, we pair a recent metabarcoding quantification approach with stable isotope analysis to examine diet composition in a wolf spider community.

3. We compare the prevalence of resource partitioning and IGP in these spiders and test whether factors that influence foraging performance, including individual identity, morphology, prey community …

Pathways Of Density Dependence And Natural Selection In Modern Humans, John Delong

School of Biological Sciences: Faculty Publications

Living things depend on a flow of energy and materials to grow, reproduce, and maintain their bodies. Populations are aggregations of individuals, so they too depend on resources. Humans use many fuels derived from the Earth’s photosynthetic energy, which in turn support a population that often occurs at unusually high densities for a mammal. Like most populations, growing human populations may experience negative feedbacks from population size unless the socio-economic system in which the population lives grows fast enough to maintain resource flows to individuals and to limit the downsides of high density. I map out a simple view of …