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Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 43
The Biosphere
(Sections 43.5 - 43.9)
Albia Dugger • Miami Dade College
43.5 Deserts
• Deserts receive less than 10 centimeters (4 inches) of rain
per year
• Most are located at about 30° north and south latitude, or in
rain shadows
• desert
• Biome with little rain and low humidity; plants that have
water-storing and conserving adaptations predominate
Desert Locations
Desert Conditions
• Deserts tend to have
low humidity, large daily
temperature shifts, and
little topsoil
Desert Conditions
O horizon:
Pebbles, little
organic matter
A horizon:
Shallow, poor soil
B horizon:
Evaporation causes
salt buildup; leaching
removes nutrients
C horizon:
Rock fragments
from uplands
Fig. 43.10, p. 730
Adaptations to Desert Conditions
• Many desert plants have adaptations, such as spines, that
reduce water loss and deter herbivory
• Some desert plants, such as cacti, store water during the wet
season, for use in drier times
• Woody desert shrubs such as mesquite and creosote have
extensive, efficient root systems
Adaptations to Desert (cont.)
• Diversity is highest in regions where moisture is available in
more than one season
• CAM plants (cactuses, agaves, euphorbs) conserve water by
opening stomata only at night when temperature declines
• Annuals have a life cycle that allows them to sprout and
reproduce in the short time that the soil is moist
Sonoran Desert Lowlands
Sonoran Desert Uplands
Perennials Adapted to Dry Conditions
Fast-Growing Annuals
Animal Adaptations
• Some animals, such as the desert kangaroo rat, minimize
water loss with highly efficient kidneys
• Most desert animals, including bats, are not active at the
height of daytime heat
• The Sonoran desert tortoise hibernates during the cold winter,
when little food is available
Two Sonoran Desert Animals
The Crust Community
• In many deserts, the soil is covered by a desert crust
(including cyanobacteria, lichens, mosses, and fungi) that
holds soil in place
• Cyanobacteria also fixes nitrogen and makes ammonia
available for plants
43.6 Grasslands
• Grasslands form in the interior of continents between deserts
and temperate forests
• Perennial grasses adapted to fire, grazing , strong winds and
infrequent rain, are the main plants in grasslands
• grassland
• Biome in the interior of continents where grasses and
nonwoody plants adapted to grazing and fire predominate
Locations of Temperate Grasslands
and Tropical Savannahs
Temperate Grasslands
• Temperate grasslands
are warm in summer,
cold in winter, with rains
throughout the year
• Grass roots help hold
thick topsoil in place,
preventing erosion by
constant winds
Temperate Grasslands
A horizon:
Alkaline, deep,
rich in humus
B horizon:
Percolating
water enriches
layer with
calcium
carbonates
A Prairie soil profile.
Fig. 43.15a, p. 732
North American Grasslands
• North America’s temperate grasslands are shortgrass and
tallgrass prairies
• Much of the American Great Plains shortgrass prairie was
plowed in the 1930s, turning the region into a “Dust Bowl”
• Nearly all tallgrass prairie has been converted to cropland
Tallgrass Prairie
Shortgrass Prairie
Savannas
• Savannas are broad belts of grasslands with scattered shrubs
and trees, that lie between tropical forests and deserts
• Temperatures are warm year-round, but rainfall is seasonal
• African savanna supports herds of hoofed grazers (such as
wildebeest) and predators that feed on them (such as lions)
African Savanna
43.7 Dry Shrublands and Woodlands
• Rains occur seasonally in dry shrublands, and lightningsparked fires sometimes sweep through shrublands during
the dry season
• Dry shrublands in California are known as chaparral
• chaparral
• Biome of dry shrubland in regions with hot, dry summers
and cool, rainy winters
Locations of Dry Shrublands
Adaptations to Chaparral
• Foliage of many chaparral shrubs has oils that deter
herbivores and also make the plant highly flammable
• Chaparral plants are adapted to occasional fires:
• Some grow back from root crowns after a fire
• Some have seeds that germinate only after they are
exposed to heat or smoke
California Chaparral
California Chaparral
• In California, where
homes are often built
near chaparral, fires
frequently cause
property damage
Dry Woodlands
• Dry woodlands prevail where the seasonal rainfall is slightly
higher than in dry shrublands
• Examples: Eucalyptus forests of Australia, and California’s
oak forests
California Oak Woodland
43.8 Broadleaf Forests
• Broadleaf (angiosperm) trees are the main plants in semievergreen forests, and in temperate and tropical deciduous
forests
• Semi-evergreen forests occur in the tropics of Southeast Asia
and India, and include broadleaf (angiosperm) trees that
retain leaves year-round, and deciduous broadleaf trees
• In semi-evergreen forests, deciduous trees shed their leaves
at the start of the dry season
Temperate Deciduous Forests
• A deciduous plant sheds leaves annually, prior to a season
when cold or dry conditions would not favor growth
• Temperate deciduous forests are found in parts of eastern
North America, western/central Europe, and parts of Asia
• temperate deciduous forest
• Northern Hemisphere biome in which the main plants are
broadleaf trees that lose their leaves in fall and become
dormant during cold winters
Locations of
Temperate Deciduous Forest
Temperate Deciduous Forests (cont.)
• Temperate deciduous forests form where 50 to 150
centimeters (20–60 inches) of precipitation falls throughout
the year
• Winters are cool and summers are warm
• Leaves often turn color before dropping in autumn
• Trees remain dormant in winter, flower and put out new
leaves in spring
Temperate Deciduous Forests (cont.)
• Rich soil and a
somewhat open canopy
lets sunlight through
and allows understory
plants to flourish
Temperate
Deciduous
Forests (cont.)
O horizon:
Scattered litter
A horizon:
Rich in organic matter
above humus layer
unmixed with minerals
B horizon:
Accumulated minerals
leached from above
C horizon:
Poorly weathered
rocks
Fig. 43.19b, p. 734
Temperate Deciduous Forests (cont.)
• Different tree species (such as oak, or beech and maple)
characterize different regions of these forests
• Animals in North American deciduous forests include grazing
deer, seed-eating squirrels and chipmunks, and omnivores
(raccoons, opossums, black bears)
Temperate Deciduous Forest
Tropical Rain Forests
• Tropical rain forests form between latitudes 10° north and
south in Africa, East Indies, Asia, South and Central America
• 130 to 200 centimeters (50 to 80 inches) of rain falls
throughout the year
• tropical rain forest
• Highly productive and species-rich biome in which yearround rains and warmth support continuous growth of
evergreen broadleaf trees
Locations of Tropical Rain Forest
Tropical Rain Forests (cont.)
• Tropical rain forest is the most productive, structurally
complex, and species-rich biome
• Photosynthesis occurs year-round; but trees often form a
closed canopy that blocks light from the forest floor
• Deforestation is an ongoing threat to tropical rain forests in
developing countries with fast-growing human populations
Tropical Rain Forests (cont.)
• Decomposition and
mineral cycling happen
fast in the warm, moist
environment
• Soils are highly
weathered, heavily
leached, and are very
poor nutrient reservoirs
Tropical Rain
Forests (cont.)
O horizon:
Sparse litter
A–E horizons:
Continually leached;
iron, aluminum left
behind impart red color
to acidic soil
B horizon:
Clays with silicates,
other residues of
weathering
Fig. 43.20b, p. 735
A Tropical Rain Forest
43.9 Coniferous Forests
• Conifers withstand harsher conditions than broadleaf trees, so
they grow farther north and at higher altitudes
• The coniferous forest that extends across northern Asia,
Europe, and North America – known as boreal forest or taiga
– is the most extensive land biome
• boreal forest
• Extensive high-latitude forest of the Northern Hemisphere;
conifers are the predominant vegetation
Locations of Coniferous Forests
Coniferous Forests (cont.)
• Conifers (evergreen trees with seed-bearing cones) such as
pine, fir, and spruce are the main plants in coniferous forests
• Conifers are adapted to conserve water during drought or
times when the ground is frozen – winters are long, cold, and
dry; and most rain falls in the cool summer
• Moose are the dominant grazers
Boreal Forest (Taiga) in Siberia
Other Coniferous Forests
• Montane coniferous forests of spruce, fir, and pine extend
southward through great mountain ranges
• Spruce and fir dominate highest elevations
• Firs and pines occupy lower elevations
• Coniferous forests in temperate lowlands along the Pacific
coast from Alaska into northern California hold the world’s
tallest trees:
• Sitka spruce to the north
• Coast redwoods to the south
Other Coniferous Forests (cont.)
• New Jersey pine barrens are a mixed forest of pitch pines and
scrub oaks that grow in sandy, acidic soil
• Southeastern pine forests hold fast-growing loblolly pines that
survive periodic fires that kill most hardwood species – these
pines are a major source of lumber and wood pulp
Montane Coniferous Forest