The Biosphere: Earth’s Diverse Environment

Chapter 34

• Ecology – the study of the interactions of organisms with their environments.

• Biosphere – extends from the atmosphere to the depths of the ocean.

• Biomes – major types of ecological associations that occupy broad geographic regions of land or water.

8 major terrestrial biomes

• Distinguished by: – vegetation– temperature – rainfall– biological community

Tropical forests

• Temperature: warm to high• Rainfall: varied - heavy• Plants: thorny shrubs, deciduous trees, &

succulents. (very diverse)• Sunlight: little reaches the forest floor.• Habitats: floor –> canopy.

– Poor soil, due to high temp & heavy rains (leaching).

• Animals: monkeys, birds, snakes, bats, frogs – tree dwelling.

Savannas

• Temperature: warm year round• Rainfall: moderate rainfall (with long periods of

drought) – BIOME DEFINED MAINLY BY THIS• Plants: grasses & scattered trees.

– growing point below ground & resistance to periods of drought.

• Habitats: migratory– Poor soil, lack of moisture, grazing animals, & fires

inhibit most trees.

• Animals: large grazing mammals, insects, burrowing animals, predators (lions & cheetahs).

Deserts

• Temperature: very hot, and cold (Antarctica) • Rainfall: dry• Plants: none, deep rooted shrubs, succulents.

– waxy coating to prevent water loss– many seeds that remain dormant until it rains

• Sunlight: extreme• Habitats: burrows, active at night• Animals: ants, birds, rodents, lizards, snakes, &

hawks.

Chaparral• Temperature: mild winter, hot summer• Rainfall: rain in winter, dry in summer• Plants: dense shrubs with tough evergreen

leaves. Seasonal plants. – Food reserves in roots allow for rapid growth after

frequent fires. – Seeds only germinate

after hot fire.

• Animals: deer, birds, rodents,

lizards & snakes

Temperate grasslands (prairies)

• Temperature: relatively cold• Rainfall: rain, but periodic severe droughts• Plants: grass, mostly treeless

– fire & grazing prevents tree growth• Habitats: bird nests on ground, burrows. • Animals: large grazing mammals (bison, wild

horses). – Soil supports diverse microorganisms & small

animals. • One of the most productive agricultural regions

in the world

Temperate (Deciduous)

forests

• Temperature: cold winter, hot summer• Rainfall: high precipitation• Plants: deciduous trees (oak, hickory, maple)• Habitats: rich soil, leaf litter, burrow• Animals: invertebrates, mice, shrew, squirrels,

birds, bobcats, foxes, bears, & mountain lions. • Most destroyed by loggers & urban

development.

Taiga (Coniferous forests)

• Temperature: long cold winters, short wet summers

• Rainfall: considerable precipitation (snow)

• Plants: cone bearing evergreens – (spruce, pine, fur)

• Habitats: soil thin & acidic

• Animals: moose, elk, bears,

wolves, hares, migratory birds.

• Heavily logged.

• Largest terrestrial biome!

Tundra

• Temperature: extremely cold• Rainfall: little• Plants: no trees, shrubs, grasses, mosses, and lichens.

– Permafrost prevents deep root penetration• Sunlight: little light for much of the winter, constant daylight

in summer• Habitats: migratory (summer is a breeding ground), high

altitude, permafrost, soil continually saturated due to poor drainage and slow evaporation.

• Animals: well insulated (oxen & caribou), lemmings, fox, snowy owl.

• During the summer, clouds of mosquitoes fill the air due to the marshy ground.

Aquatic Biomes• Oceans cover about 75% of the Earth’s surface

• Light and the availability of nutrients are the major factors that shape aquatic communities.

• photic zone is the portion of the ocean into which light penetrates.

• continental shelf where coral reefs are found in warm tropical waters.

• The pelagic zone is the open ocean

• aphotic zone is a vast, dark region of the ocean.

• benthic zone is the ocean bottom

• The pelagic zone is the open ocean

• Estuaries are productive areas where rivers meet the ocean.– They are often bordered by wetlands

• The intertidal zone is the wetland at the edge of an estuary or ocean, where water meets land

– Freshwater biomes include lakes, ponds, rivers, streams, and wetlands

Review Questions

• Describe the chemical and physical factors that affect the biosphere

• Discuss the role of abiotic and biotic factors in the survival of an organism

• Describe the characteristics of aquatic biomes

• Explain the factors contributing to the characteristics of terrestrial biomes

• Describe the eight major terrestrial biomes