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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