The Bryopsida class has a worldwide distribution, from the poles to tropical deserts and continental waters, being only absent in oceanic waters. They are common organisms, dominant in some ecosystems such as tundra or cloud forests.

Within this group are the typical mosses, with 95% of all moss species found here. Many of their species are capable of living on bare rock, making them one of the first organisms to colonize new lands and begin soil formation, promoting the establishment of higher plants. Other species can only live on specific substrates or in mature, uncontaminated forests. Species living in aquatic environments are always found in highly oxygenated areas, such as on waterfall walls or in clean, flowing streams, dying if the water becomes stagnant or oxygen levels drop.

Many of these species have the ability to dehydrate, entering a state of dormancy. Many of these species have specialized structures to retain water for as long as possible. For example, they often have lamellar or irregular expansions on the upper surface of their leaves, causing water to be retained by capillarity and delaying evaporation, thus extending the photosynthesis period. Other species have papillose extensions on the epidermal cells, creating a very irregular surface through which water rises by capillarity, promoting water from the soil to rise along the moss surface and cover the surface of the plant. Another common adaptation is to have a cushion-shaped form and a leaf ending in a long hair, creating a layer of still air between the moss and the atmosphere and delaying the evaporation of water retained by capillarity.

The following cladogram shows the evolutionary relationships of the different orders: