Land biomes are similar ecosystems that occur under similar environmental conditions, even if they are widely separated geographically. This makes them predictable and helps scientists categorize plant and animal life. Studying land biomes is a way to study the relationship between plants and animals, and how that relationship can change depending on the climate and availability of certain nutrients.
Land biomes are often categorized by the dominant vegetation that naturally occurs in them. Grasslands, as their name indicates, feature largely grass. The wildlife that inhabit the grasslands are adapted for living in or around grass. Grasslands exist in North America, and in Europe and Asia where they are called steppes. Forest biomes, of which there are several distinct types, are so called because of the trees that make up a large part of their area.
Sometimes land biomes are categorized by the lack of vegetation that occurs. For example, tundra biomes do not support trees at all and feature mostly shrubs and dwarf plants. This is generally because of the cold climate and permafrost which inhibit root growth. Desert biomes are areas with low rainfall; their animal life is specially adapted to low rainfall environments and vegetation is rare.
Non-terrestrial biomes include freshwater and marine biomes. Freshwater biomes occur in any source of fresh water -- lakes, rivers, streams and wetlands. Marine biomes include the oceans and seas. Due to the massive amount of space that salt water takes up on Earth, many marine biome subcategories exist. Anthropogenic biomes are the biomes that include human cause and effect.