Life history traits, e.g., growth rates, maturation schedules, and offspring size and number, are influenced by environmental and anthropogenic factors and in turn determine individual fitness and influence population growth rates. Because life history traits are heritable, variation in these traits tends to involve both evolutionary (genetic) and ecological (plastic) processes. Exploring life history variation provides an opportunity not only to understand the eco-evolutionary interactions that shape the observed patterns, but also to forecast population dynamics in changing environments. In this course, we design lectures to guide students to understand the concepts and theories of adaptive life history variation. In addition, we design a course project that involves field sampling and laboratory experiments with mosquitofish Gambusia affinis, allowing students to gain hands-on experience on life history research. The objectives of this course are to 1) understand the theoretical background of life history variation, and 2) explore empirical variation in growth rates, maturation schedules, and offspring size and number based on the model species, mosquitofish.