22.4 Biomes page 758• Key Concepts: What are the six major biomes

found on Earth? What factors determine the type of biome found in an area? What do freshwater and marine ecosystems include?• Key terms: biome, canopy, understory, desert,

grassland, savanna, deciduous tree, coniferous tree, tundra, permafrost, estuary, intertidal zone, neritic zone

Biomes

• A biome is a group of land ecosystems with similar climates and organisms• The six major biomes that most

ecologists study are the rain forest, desert, grassland, deciduous forest, boreal forest, and tundra

• It is mostly the climate – temperature and precipitation – in an area that determines its biome.

Rain forest biomes• Temperate rain forests – have moderate temperatures• Northwestern coast of US receives more than 300 cm of rain per year.

Huge trees grow.

• Tropical rain forests – regions close to the equator• Canopy – leafy roof area• Second layer – understory• Forest floor

Desert biomes• Deserts are areas that receive less than 25 cm of

rain per year • The amount of evaporation in a desert is greater

than the precipitation. • Often undergo shifts in temperature from day to

night

• Organisms have to be accustomed to little rain and huge temperature differences

Grassland biomes• Prairies• Temperatures are more comfortable than

the desert• Gets more rain, but not enough for trees to

grow• Area that is populated mostly by grasses

and other non-woody plants• Most receive 25 to 75 cm of rain per year

• Savannas receive 120 cm of rain per year and are located close to the equator

Deciduous forest biomes

• Deciduous trees – trees that shed their leaves and grow new ones each year. Oaks and maples for example. • Forests receive enough rain to support

tree growth, at least 50 cm per year. • Temps vary greatly• A lot of wildlife, but not during the

winter.

Boreal forest biomes

• Colder climates• Boreal forest plants – coniferous trees – trees that produce their

seeds in cones and have leaves shaped like needles. • Boreal forest is sometimes referred to by its Russian name, the taiga. • Trees are well adapted to cold• Animals – eat the seeds produced by the coniferous trees.

Tundra biomes• Tundra – extremely cold and dry biome. May receive

no more precipitation than a desert. Most of the soil in the tundra is frozen all year. The frozen soil is called permafrost.

• Tundra plants – mosses, grasses, shrubs

Mountains and ice

• Some places are covered year round with ice, like mountain ranges.• These areas are not considered part of any particular biome.

Freshwater ecosystems

• Freshwater ecosystems include streams, rivers, ponds and lakes.

Marine Ecosystems

• Estuary – found where fresh water of a river meets the salt water of the ocean• Marine ecosystems include estuaries, intertidal zones, neritic zones,

and the open ocean.

Intertidal zones

• The area between the highest high-tide line and the lowest low-tide line. • Organisms survive pounding waves and sudden changes in water

levels and temperatures.

Neritic Zones

• Below the low-tide is a region of shallow water which extends over the continental shelf. • Photosynthesis can occur here.

Open Oceans

• Light penetrates only a few hundred meters deep. • The deep zone is located below the surface zone. The deep zone is

almost totally dark.