Wallace’s Realms or Biotic Provinces

• Inhabited by characteristic set of taxa (groups)

• Bounded by barriers that prevent spread of distinctive kinds of life

• Organisms in a biotic province share common genetic heritage

• Explained by continental drift, caused by plate tectonics

Wallace’s Realms or Biotic Provinces

Moving Species Rules

• Moving between different areas of the same biome within the same realm is the most likely to result in a successful introduction

• Moving species between similar biomes in different realms can also result in successful introductions

• Moving species between realms and between biomes of different types is less likely to result in successful introductions

Rule of Climatic Similarity

Global Distribution of Major Land Biomes

Biomes

• A biome is a terrestrial ecosystem each biome is characterized by a particular climate

and a defined group of organisms the biomes differ remarkably from each other but

show many consistencies within• a particular biome often looks similar, with many of the same

creatures living there, wherever it occurs on the earth

there are seven major and seven minor biomes distributed throughout the earth

• biomes that normally occur at high latitudes also follow an altitudinal gradient along mountains

Figure 37.25 Distribution of the earth’s biomes

Tropical Rain Forest• Tropical rain forests

are the richest ecosystems on earth

• Communities in these forests are very diverse in that each type of organism is represented by a few individuals

Rain forests receive over 100 inches of rain per year and have the most diverse group of organisms found anywhere on earth.

At least half of all the described species inhabiting earth live there, and half of those are threatened with extinction in the next few years.

Extensive tropical rain forests are found in South America, Africa, and Southeast Asia.

Many of the animal species live in the trees. There is a particularly high diversity of insects.

Tropical Rain Forest

Tropical Rain Forest

Savannas• Savannas are

grasslands that have widely spaced trees and seasonal rainfall

• This biome is a transition between tropical rain forest and desert

Savannas are grasslands bordering the tropical rain forests.

They receive less rain, typically 30 to 50 inches per year, and are transitional between rain forests and desert areas.

Large numbers of grazing mammals characterize savannas.

Many savannas are being converted to agricultural land for human use, to the demise of the natural inhabitants.

Deserts• Deserts are dry

places with sparse vegetation

• Plants and animals may restrict their activity to favorable times of the year, when water is present

Deserts are the world's great hot and dry areas, with less than 10 inches of rainfall per year.

Vegetation is sparse, and many unique adaptations for water conservation can be found.

Desert animals are nocturnal or, like the camel, can store large quantities of water or are extremely efficient at water conservation like the kangaroo rat.

Grasslands or Prairies• Grasslands (also

called prairies) grow in temperate areas

• Most of the original grasslands have been converted to use by agriculture

Temperate grasslands, or prairies, cover much of inland North America, Eurasia, and South America.

They are found roughly midway between the equator and either pole.

In North America, much of the native prairie has been converted to rich agricultural land.

Herds of grazing mammals such as bison used to roam the area until much land was converted to agricultural use.

Temperate Deciduous Forests• Deciduous forests

are forests of trees that drop their leaves in the winter

Deciduous forests are found in areas with mild climates in Eurasia, the northeastern United States, and eastern Canada.

Deciduous, hardwood trees drop their leaves in the winter.

Only remnants of the once great forests now remain.

Many animals, such as deer, raccoon, and beaver, characterize this biome.

Temperate Rain Forest• At least 200 cm of it, perhaps

up to 350 centimeters in warmer areas. 

• The precipitation can fall in the form of rain or snow, with snow becoming more likely at higher elevations. 

• The average annual temperature is above 0° C, largely influenced by the nearby ocean and may be as warm as 20° C

Located in northwestern coast of North America from northern California though southern Alaska.  There are also small areas in southern Chile, New Zealand, Australia and a few other places around the world.

Big coniferous trees dominate this habitat, including Douglas fir and Western red cedar, Mountain hemlock, Western hemlock, Sitka spruce and Lodgepole pine.  Mosses and lichens are very common, often growing as epiphytes. 

Taiga or Boreal• The taiga is a great

ring of coniferous trees that extends across vast areas of North America and Asia

• Most of the trees occur in dense stands of one or two species

Taiga, or northern coniferous forest, is found in the colder regions of the north.

Coniferous trees have needlelike leaves that remain on the tree throughout the year.

Marshes and lakes are common in taiga, and most of the precipitation falls during the short summer months.

Large mammals, such as elk, moose, deer, bears, and wolverines, inhabit taiga.

Tundra• Tundra is open, often

boggy, grassland that occurs in the far north beyond the taiga

• Permafrost, or permanent ice, usually exists within 1 meter of the surface

Tundra is even further north than taiga, surrounding the poles of the earth. Precipitation is low there, and a layer of permanently frozen soil, called permafrost, is present year-round. Trees are small and found on lake shores. Large grazing mammals, such as musk oxen, caribou, and reindeer, seem to thrive in the tundra, and

carnivores, such as wolves, foxes, and lynx, manage to survive too. Lemmings experience population cycles, and serve as a predominant food source for predators.

Minor biomes

• There are three additional minor biomes mountain (alpine) zone

• similar to tundra but at high altitude temperate evergreen forest

• occurs in regions where winters are cold and there is a seasonal dry period

– Sub-type: Temperate Rain Forest

warm, moist evergreen forest• occur in regions where winters are mild and

moisture is plentiful