This Research Infrastructure Improvement (RII) EPSCoR Research Fellows project provides a fellowship to an Assistant Professor and training for a graduate student at the University of Kentucky. This work is conducted in collaboration with Dr. Shripad Tuljapurkar at Stanford University. Through the fellowship, the PI will investigate how organisms allocate energy to growth, survival, and reproduction across their life cycles. The research will examine why species that differ greatly in body size, lifespan, and metabolic rate can nevertheless achieve similar long-term reproductive success. To address this question, the project will advance a new scientific framework called the Equal Fitness Paradigm, which links metabolism of organisms to life history, population dynamics, and energy flows in ecosystems. By combining approaches from ecology, physiology, and population biology, the project will improve understanding of the fundamental processes that shape the diversity of life on Earth. The work will strengthen collaboration between Kentucky and Stanford researchers, train students in quantitative ecological methods, and develop open-source data tools that support research, education, and applied natural resource management. This project will integrate numerical and metabolic theories of life history to advance the Equal Fitness Paradigm (EFP), a framework that links energetic constraints to life history evolution and population dynamics. The research will develop mathematica