Biology Chapter 4

boreal forest

Along the northern edge of the temperate zone are dense evergreen forests of coniferous trees. these biomes are also called taiga. winters are bitterly cold, but summers are mild and long enough to allow the ground to thaw. the word boreal comes from the greek word for "north" reflecting the fact that this biome occur mostly in the northern hemisphere.

Tropical savanna

Receiving more seasonal rainfall than deserts but less than tropical dry forests, this biome, also known as grasslands are characterized by a cover of grasses. savannas are spotted with isolated trees and small groves of trees and shrubs. compact soils, fairly frequent fires, and the action of large animals such as rhinoceroses prevent some savanna areas from turning into dry forest.

Tropical Rain forest

The home to more species than all other biomes combined. the leafy tops of tall trees-extending from 50 to 80 meters above the forest floor-form a dense covering called canopy. in the shade below the canopy, a second layer of shorter trees and vines forms an understory. Organic matter that falls to the forest floor quickly decoposes, and the nutrients are recycled.

desert

These biomes are dry- in face this biome is defined as having annual precipitation of less than 25 centimeters. beyond that, they vary greatly, depending on elevation and latitude. many undergo extreme temperature changes during the course of a day, alternating between hot and cold. the organisms in this biome can tolerate the extreme conditions.

Temperate forest

These forests contain a mixture fo deciduous and coniferous trees. coniferous trees, or conifers, produce seed-bearing cones, and most have leaves shaped like needles. these forests have cold winters that halt plant growth for several months. in autumn, the deciduous trees shed their leaves. in the spring, small plants burst out of the ground and flower. soils of temperate forests are often rich in humus, a material formed from decaying leaves and other organic matter that makes soil fertile.

tropical dry forest

These forests grow in places where rainfall is highly seasonal rather than year-round. during the dry season, nearly all the trees drop their leaves to conserve water. A tree that sheds its leaves during a particular season each year is called deciduous.

tundra

This biome is characterized by permafrost, a layer of permanently frozen subsoil. during the short, cool summer, the ground thaws to a depth of a few centimeters and becomes soggy and wet. in winter the topsoil freezes again. this cycle of thawing and freezing, which rips and crushes plant roots, is one reason that this biomes plants are small and stunted. cold temperatures, high winds, the short growing season, and humus-poor soils also limit plant height.

photic zone

a zone where photosynthesis is limited to this well-lit upper layer

wetland

an ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year

predation

an interaction in which one organism captures and feeds on another organism

symbiosis

any relationship in which two species live closely together

opean ocean zone

begins at the edge of the continental shelf and extends outward, largest marine zone, high pressures, frigid temps., and total darkness, has very low levels of nutrients and supports only the smallest producers

aphotic zone

below the photic zone, is permanently dark, chemosynthetic autotrophs are the only producers that can survive in this zone

mutualism

both species benefit from the relationship

mangrove swamp

coastal wetlands that are widespread across tropical regions including southern florida and hawaii

estuary food web

differs from other ecosystems because most primary production is not consumed by herbivores, instead much of the organis material enters this as detritus

coastal ocean

extends from the low-tide mark to the outer edge of the continental shelf, the relatively shallow border that surrounds the continents

primary succession

on land, succession that occurs on surfaces where no soil exits

commensalism

one member of the association benefits and the other is niether helped nor harmed

parasitism

one organism lives on or inside another organism and harms it

abiotic

physical or nonliving factors that shape ecosystems

biotic

the biological influences on organisms within an ecosystem

niche

the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions

benthic zone

the ocean floor, extends horizontally along the ocean floor from the coastal ocean through the opean ocean, includes benthos organisms that live attached to or near the bottom

estuaries

wetlands formed where rivers meet the sea

secondary succession

when the disturbance is over, community interactions tend to restore the ecosystem to its original condition