Albia Dugger • Miami Dade College

Cecie StarrChristine EversLisa Starr

www.cengage.com/biology/starr

Chapter 43The Biosphere

(Sections 43.5 - 43.9)

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

Fig. 43.10, p. 730

C horizon:Rock fragmentsfrom uplands

B horizon:Evaporation causes salt buildup; leaching removes nutrients

A horizon: Shallow, poor soil

O horizon:Pebbles, littleorganic matter

Desert Conditions

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 Grasslandsand 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

Fig. 43.15a, p. 732A Prairie soil profile.

B horizon: Percolating water enriches layer with calcium carbonates

A horizon: Alkaline, deep, rich in humus

Temperate Grasslands

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 lightning-sparked 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 semi-evergreen 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

Fig. 43.19b, p. 734

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 weatheredrocks

Temperate Deciduous

Forests (cont.)

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 year-

round 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

Fig. 43.20b, p. 735

A–E horizons: Continually leached; iron, aluminum left behind impart red color to acidic soil

O horizon:Sparse litter

B horizon: Clays with silicates, other residues of weathering

Tropical Rain Forests (cont.)

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