A World of Diversity

General Ecology

Specific Ecosystems

Biomes

Rainforests Savannas and deciduous forests Deserts Grasslands Temperate deciduous forests Temperate mixed and Coniferous forests Mediterranean scrub Taiga Arctic tundra

Areas of ecological difference in the plant and animal species such as a desert or rain forest can be classified as a specific type of biome. A biome is a set of terrestrial ecosystems, which are climatically controlled and have distinctive vegetation. Within this set of ecosystems there is an exchange of nutrients and biological components such as plants and animals. These plants and animals have very distinct adaptations to the specific climate in which they are situated. Although the various biomes of the world may be widespread on several different continents, the plants which compose them are very similar due to parallel evolution, which was influenced be the specific climatic conditions that they were exposed to.

These various biomes can be classified in a number of ways. In Europe the term biome is not used. The proper term is plant formations. The major difference between a plant formation and a biome is that a biome includes the associated animals of the group of ecosystems. It is this varied idea of how to classify the plant formations or biomes which leads to several different classification systems. The nine biomes, which are discussed on this web site, are those, which will provide an overview of all of the vegetation of the world.

To understand the differences of the world’s biomes and what they are composed of a general understanding of how plants and animals survive on land and the different weather patterns and geological formations of the earth will be necessary.

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Although oxygen and carbon dioxide are more available, life for plants and animals on land is not easy. Plants and animals on land have to deal with the effects of gravity and climatic changes, along with poor growing conditions and soils. Although plants and animals have several disadvantage placed on them the number and diversity of species is amazing. These species are found in a wide variety of biomes whose distribution is controlled by three factors. First the distribution of heat from the sun, and the various seasons of an area, is it always warm with even sun year round like near the equator or does the amount of sun change and there are distinctive seasons like in the northern Untied States and Europe. Secondly, the pattern of global air circulation and which way the winds containing moisture blow. Third, the various geological features such as mountain ranges and their orientation.

It is this third factor, geological features of the world along with location, which creates much of the diversity of the world. Mountain ranges in the northern hemisphere affect the amount of inland precipitation, air which is filled with moisture from the ocean flows east across the mountains where it rises and cools condensing the water vapor and causing it to rain. This pattern of airflow creates a moist environment on the western side of the mountains and a dry rain-shadow effect in the east.

Along with geography location in latitude and altitude affects plant and animal species. An increase in altitude, such as climbing a mountain is similar to heading north (in the northern hemisphere) plant and animal species will be similar at a mountain top to those which are further north. As one can see there are many factors which affect plant and animal diversity creating the various biomes of the world. As one would expect the complex interactions at local levels will create environments, which are different from any other environment in the world. For this reason we will discuss each of the various biomes in general terms to give an overview and better understanding of the diversity of life on earth. The names and definitions for all of theses biomes has been presented in a similar fashion in Biology of plants, sixth edition.

Biomes of the World

Biome	Temperature and Precipitation	Characteristic Plants	Miscellaneous Features

Rainforests	High temperature and high rainfall year round.	Broad-leaved evergreen trees, epiphytes, and lianas.	The biome with the greatest diversity of species. Infertile soils.
Savannas and deciduous tropical forests	High temperature and seasonal drought.	Grasslands with scattered broad-leaved deciduous or evergreen trees or shrubs.	Periodic burning is an important aspect.
Deserts	Precipitation generally very low except for occasional peaks; maximum temperature varies with the type of desert.	Succulents such as cacti; annual herbs.	Adaptations include small leaves, thick cutickles, and photosynthetic rates with high maximum temperatures.
Grasslands	Moderately low precipitation; cold winters and warm summers.	Perennial bunchgrasses and sod-forming grasses.	Heavily exploited for agriculture.
Temperate deciduous forests	Moderate precipitation evenly disributed; cool winters and warm summers.	Deciduous trees and many perennial herbs.	The dominant herbaceous plants vary with the seasons.
Temperate mixed and coniferous forests	Moderately low precipitation and moderately cold winters.	Mixtures of deciduous trees and conifers.	Occur as a transition zone north of the deciduous forest. Also found in areas with nutrient-poor soils or with less seasonal environments.
Mediterranean scrub	Cool, moist winters and hot, dry summers.	Evergreen or summer-deciduous, drought-resistant trees and shrubs in dense thickets.	Called chaparral in California and maquis around the Mediterranean Sea.
Taiga	Moderately low precipitation and cold winters, although in the Pacific Northwest the winters are very wet.	Forest of evergreen trees.	Soils are highly acidic and very low in nutrients. Permafrost may be present.
Arctic tundra	Very low precipitation in both summer and winter; very cold winters.	Low shrubs, grasses, sedges, and lichens.	Permafrost present throughout. Much of the biomass is underground.