Biomes as Units of the Biosphere

Merriam-Webster dictionary defines biosphere as "the part of the world in which life can exist." There are 2.1 million catalogued species known to exist and some scientist estimate as much as 100 million might exist. Each of these species has adapted to life in a particular part of the biosphere. These particular parts are called ecosystems. Since there is a large jump between the biosphere and ecosystems scientists have divided the biosphere into biomes.

In doing research about biomes, it seems that different scientists have different ideas about biomes. They vary in their number just as they vary in their names. Biomes could be called units of the biosphere and each biome is made up of many ecosystems. There are obviously many types of biomes in this world because of the diversity of climates around the world. The fewer number of biomes you choose to say make up our ecosystem, the more general they become. Some scientists obviously believed that more types of biomes are needed to describe the variety of climates in our world.

Some name as few as six biomes to describe the different areas of our biosphere but others name as many as twelve or more. I believe that six is sufficient but there are what you might call sub-biomes of each biome that some would like to differentiate from the others like them.

The taiga biome is the largest of the biomes. It is located in Canada, Europe and Asia. The average temperature of the taiga is below freezing about 6 months out of the year with about 12 to 33 inches of precipitation per year. There is little diversity in plant life. A few broad leaf tree species live in the taiga but mostly evergreen trees are the only ones that have adapted to really thrive in this environment. There are some animals that have adapted to live in the cold and snowy environment. A predator called the ermine has a thick coat of dark fur that turns white in the winter. The snowshoe rabbit also has a fur that turns white in the winter. The wolverine is able to mate during ideal conditions by delayed implantation in which they suspend dormant fertilized eggs until the conditions are ideal for bearing their young.

Rainforests are the most diverse having more than 15 million species living in the biome. The rainforest biome is sometimes separated into two different biomes. They are referred to as tropical and temperate. The tropical rainforests are located between the Tropic of Cancer and the Tropic of Capricorn. More than half are in Latin America and about a third are in Brazil. The rest are in Southeast Asia and West Africa. Temperate rainforests are located along the Pacific Coast of North America stretching from Oregon to Alaska and in South America along the coast of Chile. They are other small areas found along the coasts of Australia, United Kingdom, Norway, Japan and New Zealand.

The tropical rainforest is composed of layers. The tallest trees form the emergent layer that reach above the rest of the trees around them. The canopy is the layer of trees that catch most of the sunlight and many animals and some small plants live in this layer. The next layer is the understory that is made up of the smaller trees and bushes that have adapted to require little light to survive. The rainforest is so dense that virtually no sunlight reaches the forest floor. Plants that live here have adapted to either grow very tall or grow without sunlight. Fungi thrive in the warm, moist and dark forest floor. The animals that live here must be tough because of the dangerous environment full of predators, poisonous snakes, and other dangers. The tropical rainforest is home to many exotic animals such as the flying dragon. This lizard has built in flaps of skin that it uses to glide to safety from a predator or just to move from tree to tree. The Indian cobra is a venomous snake that has developed markings on its hood resembling eyes and can spit its venom into the eyes of an opponent. The chimpanzee, orangutan, and gorilla also live in the tropical rainforest.

The temperate rainforest is less diverse being dominated by only four coniferous trees; the Douglas fir, the Sitka spruce, the western red cedar, and the western hemlock. The Douglas fir stands up to 300 feet tall. The Sitka spruce and the western red cedar can both live to be over 1000 years old. The forest floor is thick with vegetation unlike the tropical rainforest. Raccoons, bears, cougars and deer are some of the animals living in this biome. The elk were once endangered but are now repopulating the forests. Areas that receive less rain than forests are grasslands.

The grasslands biome covers about one quarter of the land on earth. Grasslands are found on every continent. This biome can also be divided into separate biomes. Tropical grasslands are those found closest to the equator and are hot all year round. Temperate grasslands are those grasslands that are farther from the equator and have cold harsh winters along with hot summers. There are about 11,000 different species of grass that grow throughout the grasslands. Grasslands are caused by the amount of precipitation that falls. Average precipitation is ten to thirty inches per year. That is little more than in the desert. This is enough to support grass but not enough to support trees. Therefore, they usually exist between forests and deserts. Grasslands can also be divided into tall, medium, and short grasslands. The height of the grass is usually the product of the amount of water available. Grasses have adapted to live under harsh conditions. During a drought the plants become dormant. New shoots emerge when rain falls. Also, grasses grow from the ground up as opposed to branching out and can be eaten or cut and still continue to grow. Because of their rich soil, grasslands make great farmlands. Large animals that live in this biome usually stay in herds because of the wide open spaces. The bison lived off the grasslands of North America until they were brought close to extinction by European settlers. Now the population has been built up in reserves but they no longer live in the wild. The African elephant takes advantage of the rolling plains of grass and eats over 400 pounds of plants every day. Lions live in groups of about twenty and work together to drive and kill prey. The prairie dog is a pest of the grassland and destroys many cattle ranges in North America. The black-footed ferret feeds mainly on prairie dogs but since farmers have started poisoning the prairie dogs, the ferrets have become endangered. Hyenas are also considered pests because they kill livestock. Grasslands that receive less rain become deserts.

The desert biome can actually be separated into hot deserts and cold deserts. They both get less than ten inches of precipitation per year but in different