An ecologist is a scientist who studies the interactions between organisms and their environments. Ecologists study how organisms interact with each other and with their physical environment, and how these interactions affect the distribution and abundance of organisms. They also study how ecosystems change over time, and how human activities can affect ecosystems. Ecologists work in a variety of settings, including universities, government agencies, and private companies. They use a variety of methods to study ecosystems, including field observations, experiments, and computer modeling.