Grasslands and related ecosystems are home to various populations of organisms that play important roles in the biosphere. These include plants, animals, fungi, and microorganisms all of which interact with one another to create a complex web of life. Plant species such as grasses, forbs, shrubs, and trees form the foundation for these communities by providing food sources for many animal species. In turn, animals provide valuable nutrient inputs through their feces or carcasses that help promote plant growth and soil health. Additionally, fungi and microorganisms serve essential functions within these systems including decomposition of organic matter and cycling nutrients back into the ecosystem for other species to use.

The most dominant population in grassland ecosystems is typically composed of herbivorous mammals such as bison, deer, elk, pronghorn antelope , prairie dogs , rabbits , mice , voles , ground squirrels , pocket gophers , skunks , coyotes , foxes etc.. Herbivores play a major role in creating habitat structure by grazing on vegetation–thus preventing it from becoming too dense–and creating pathways via their movement patterns that allow access to resources otherwise inaccessible under entrenched tree canopies or low-lying brush forms. Furthermore they act as prey items supporting populations of larger predators such as cougars wolves bobcats lynx eagles hawks owls etc.. These animals occupy higher trophic levels where they primarily feed on smaller herbivores but also scavenge carrion when available . This helps recycle nutrients quickly allowing them to be reused repeatedly throughout the system rather than left behind from plant decay processes which take much longer .