Biology Now, 2e

384 ■ CHAPTER 21 Ecosystems

ECOLOGY

The tundra biome is found at the poles

and on mountaintops. Trees are absent

or scarce because of the short growing

season. The vegetation is dominated

by low-growing flowering plants, and

the boggy landscape is covered in

mosses and lichens, important food

sources of herbivores. Rodents provide

food for carnivores like foxes and

wolves. Bears and musk oxen are

among the few large mammals.

The boreal forest is

dominated by coniferous

trees that grow in northern

or high-altitude regions with

cold, dry winters and mild

summers. The soil is thin

and nutrient-poor, so while

plants generally receive

adequate moisture during

the growing season, plant

diversity is relatively low.

Large herbivores include elk

and moose. Small

carnivores, such as weasels,

wolverines, and martens, are

common. Larger carnivores

The chaparral is a shrubland include lynx and wolves.

biome dominated by dense

growths of drought-resistant

plants in regions with cool,

rainy winters and hot, dry

summers. These conditions

make the chaparral

exceptionally susceptible to

wildfires. Common vegetation

in the California chaparral

includes scrub oak, pines,

mountain mahogany,

manzanita, and the chemise

bush. Small mammals such as

jackrabbits and gophers are

common, and there are many

species of lizards and snakes.

The tropical forest biome is characterized by warm

temperatures, about 12 hours of daylight each day, and

either seasonally heavy or year-round rains, which tend

to leach nutrients from the soil. Soils in this biome

further tend to be nutrient-poor because a large

percentage of nutrients are locked up in the living

tissues (biomass) of organisms. Tropical rainforests,

which may receive in excess of 80 inches (200 cm) of

rain annually, are some of the most productive

ecosystems on Earth, with a rich diversity of organisms.

Ecosystems within the freshwater biome are heavily

influenced by the terrestrial biomes that they border or

through which their water flows. Lakes are landlocked bodies

of standing freshwater. Rivers are bodies of freshwater that

move continuously in a single direction. Wetlands are

characterized by standing water that is shallow enough for

rooted plants to emerge above the water surface. A bog is a

freshwater wetland with stagnant, oxygen-poor water, and

low productivity and species diversity. In contrast, grassy

marshes and tree-filled swamps are highly productive

wetlands with a high diversity of organisms.

Tundra

Boreal forest

Temperate forest

Grassland

Chaparral

Desert

Tropical forest

Terrestrial biomes: