What is a biome?

It is defined as a definite community of animals and plants residing together in a climate. Each (plants and animals) having a characteristic appearance and distributed over a wide geographical area defined largely by regional climatic conditions.

The biome concept was first given by F.E. Clements and V.E. Shelford in 1939. The term was given for the broad-scale distribution of world vegetation and associated animals. It is a broader term than 'habitat'. It can comprise a variety of habitats and it is the largest geographical biotic unit.

Biome and its Distribution in the Ecosystem

An ecosystem includes an area where plants and animals live together and interact with abiotic factors. An ecosystem is of different types: natural ecosystem, forest ecosystem, grassland ecosystem, freshwater ecosystem, marine ecosystem. For example, a forest is an ecosystem with a very high density of trees. 

The distribution of biome is affected by two factors:

• Precipitation
• Temperature 

Classification of Biome

• Biome classification is based on their vegetation. It is mainly done in terrestrial and aquatic biomes.
• The major terrestrial biomes include tropical rainforests, deserts, tropical grassland which is known as savannas, temperate grassland, coniferous forests which are also known as taiga or boreal forests. Terrestrial ecosystems are those that are found on land. A forest is a complex ecosystem.
• Aquatic biomes are those that are found in water.
• Grassland ecosystems are dominated by perennial grass species. The climax vegetation of the grassland biome is grass, although the species vary in grassland biomes located in different geographical regions.

Tundra Biome

Tundra is a polar desert where extreme climatic conditions prevail such as low temperature, low precipitation, strong wind and long periods of shortage of water. 

Three types of tundra biome are:

• Antarctic Tundra
• Alpine Tundra
• Arctic Tundra 

• The Antarctic tundra biome is present in Antarctica and different Antarctic islands. It is too cold and dry to support vegetation.
• The Arctic tundra biome is characterized by a short growing season, low precipitation, and permanently frozen deeper soil called permafrost. Plant life consists of grasses, sedges (arctic cotton), and lichens. Trees are absent. Climate keeps fluctuating in this biome.
• The alpine tundra is present high on the mountain. They are characterized by widely fluctuating temperatures, strong winds, and snow.

Tropical Grassland or Savanna Biome

Tropical grassland also known as savanna is composed of large grasses with scattered trees. The treeless area of South America is also known as Savanna. It is generally formed due to changes in the climate. The amount of rainfall and precipitation determine the nature of vegetation. In the hot and warm climates where the annual rainfall is 30-50 cm the tropical grassland are found. In this region, the soils are porous, with a very thin layer of nutrients rich matter called humus. The evolution of plant characters in savannas is dominated by three selective forces. These forces include grazing, periodic drought and recurring fire. Frequent fires are observed in the savanna.

Taiga Biome

The taiga biome is also known as the coniferous forest biome or boreal forest biome. It is the largest terrestrial biome on earth which is located near the polar region. The taiga biome is generally present near the higher latitudes. In this biome precipitation mainly occurs as snow. The climate varies in this biome. It is characterized as long and cold winters and short and cool summers.

Temperate Grasslands

They have grasses as the dominant vegetation. In this, the shrubs are large in size and trees are not present. As compared to the savanna the amount of rainfall is less in temperate grassland. Seasonal drought and occasional fires are very important in shaping the biodiversity of savanna but, their effect is not as visible in temperate grassland as they are in the savanna. Further, the temperate grassland is sub-divided into prairies and steppes. Prairies have tall grasses and steppes have short grasses. The abundance of tall grasses with high biodiversity is due to high precipitation.

Tropical Rainforest

In tropical rainforest high temperature and high rainfall prevails. In this biome, there is more diversity of species. Geographically the climate of tropical rainforest changes but is mainly characterized by a mean temperature. The minimum monthly precipitation is above 6cm. The vegetation of tropical rainforests is characterized by evergreen, hygrophilous, tall and rich in lianas and epiphytes.

Tropical rainforests are characterized by the dominance of woody plants mainly trees, relatively slender trunks compared to trees of temperate forests, high species richness, sparse undergrowth. The canopy (umbrella-like structure formed by trees) in tropical forests is multi-layered and continuous, allowing little light penetration. The dominant plants are phanerophytes, trees, lianas and epiphytes. The largest region of rainforest in the world is in the Amazon basin of South America. High variation in plant and animal species is present in the tropical rainforest. The tropical rainforest occupies 6 percent of the total earth’s surface which accounts for 50 percent of plants and animal species.

Temperate Deciduous Forest

Temperate deciduous biomes include broad-leaved trees that lose their leaves every year. The temperate deciduous forest is characterized by a distinct season that includes a long growing season together with a cold winter season in which much of the dormant vegetation is present. Temperate climates have four seasons: winters, spring, summer and fall. The temperature varies from season to season, with cold winters and hot, wet summers. Temperatures fall below freezing each winter. The average yearly temperature is about 10°C.

Chaparral Biome

The chaparral biome is the name given to the evergreen sclerophyll's'.  Sclerophylls' vegetation possesses small leaves, thick cuticles, sunken stomata, glandular hairs. These structures or characteristics are generally present in the plant to minimize the loss of water. It is mainly characterized by mild, rainy winters and long and dry summers. IN North America, the sclerophylls' shrub community is known as 'chaparral'. It is a shrubland biome, where shrubs and short trees are present. In general, a shrub is a plant with multiple woody, persistent stems but no central trunk. Annual precipitation generally falls within the range of 30-50cm. 

Context and Application

This topic is important for both Bachelors of science and Master of science entrance Exam as well as medical entrance exams:

• Bachelors in Botany
• Masters in Botany