BIOMES AND AQUATIC ECOSYSTEMS Chapter 44 A Biomes

BIOMES AND AQUATIC ECOSYSTEMS Chapter 44

A. Biomes Major types of terrestrial ecosystems. Distribution of biomes largely depends on climate (temperature & rainfall). Climate is determined by the Earth’s tilt & uneven heating of Earth’s surface. Tilt produces seasons in northern & southern hemispheres.

Unequal heating causes air movements that distribute moisture. Altitude influences climate - conditions usually become drier & colder as altitude increases.

1. Tropical Rain Forest ] warm & moist (rainfall: 79 -157 in/yr) ] nutrients cycle rapidly ] soils are nutrient poor ] plants exhibit vertical stratification ] very high biodiversity

2. Tropical Dry Forest ] wet & dry seasons ] temperature fluctuates ] soils are rich in nutrients ] organisms adapted to seasons

3. Tropical Savanna ] wet & dry seasons (rainfall: 12 -20 in/yr) ] mainly grasslands; few scattered trees & shrubs ] organisms adapted to wet/dry seasons (migrating herbivores) ] frequent fires maintain grassland

4. Desert ] dry (rainfall: < 8 in/yr) ] hot days / cool nights ] plants adapted to obtain & store water F rapid life cycles F deep roots (mesquite) F succulent tissues / reduced leaves (cacti)

] animals adapted to minimize water loss F tough, waterproof integument F concentrated urine F nocturnal habits F halophytes Atriplex (saltbush plant) stores salt in outer cells of leaves. Red vizcacha rat has adaptation that allows it to feed on Atriplex.

5. Temperate Grasslands (prairie) ]1 or 2 dry seasons/year (rainfall: 10 -40 in/yr) ] lack trees & shrubs ] grazing & frequent fires maintain grass In US, majority of prairie has been replaced by farmland.

6. Temperate Forests rainfall: 26 -118 in/yr Temperate forests are either deciduous or coniferous. Temperate Deciduous Forest oak-hickory or beech-maple predominate ] moist growing season (at least 4 months) ] soil rich in nutrients ] vertical stratification ] organisms adapted to seasonal changes ]

Temperate Coniferous Forest spruce, pines, firs & hemlocks predominate ] summers typically dry; long, harsh winters ] soil is thin, acidic & poor in nutrients ] understory of shrubs ] adapted to recurring fires ]

7. Taiga (boreal forest) ] precipitation falls as snow/ice (8 -24 in/yr) ] long, cold winters ] soil is thin, moist, acidic & nutrient poor (subsoil may be frozen) ] biodiversity lower than temperate zone ] conifers predominate

8. Tundra Precipitation: 8 -24 in/yr ] long, bitterly cold winters ] permafrost begins 18 in. below surface ] low biodiversity ] shallow-rooted shrubs & lichens ] plants adapted to short growing season ] animals adapted to cold (small extremities) & snow (many are camouflaged)

B. Aquatic Ecosystems 1. Freshwater Ecosystems ] Lakes and Ponds (standing water) F littoral zone F limnetic zone F profundal zone F benthic zone

Oxygen & nutrients (nitrogen/phosphorus) are unevenly distributed in lakes. F O 2 level is highest near surface F nutrient level is highest near bottom Oxygen & nutrients are redistributed by: F wind (ponds & shallow lakes) F fall & spring turnover (deep lakes in temperate regions)

Oligotrophic lakes F young; low in nutrients & productivity F clear & sparkling blue F deep water is oxygen-rich Eutrophic lakes F older; nutrient rich & high in productivity F green & murky F O 2 often depleted in deep water during summer Nutrients in sewage & agricultural runoff cause eutrophication.

] Rivers and Streams (running water) Transport rainwater, groundwater, snowmelt & sediment from land to ocean or lake. At headwaters: F channel is narrow F water is clear & oxygen-rich F current is swift At mouth: F channel widens F water is murky & contains less oxygen F current slows, depositing sediment

2. Marine Ecosystems ] Coastal Ecosystems Include estuaries, mangrove swamps, the intertidal zone & coral reefs. Estuary - area where fresh water of river meets salty water of ocean. F water is brackish F salinity fluctuates F very productive F high biodiversity F nursery for many ocean animals

Mangrove Swamp - tropical wetland dominated by salt-tolerant plants (mangroves). F transitional zone between forest & ocean F salinity fluctuates F plants have aerial roots F high biodiversity

Intertidal Zone - area along coast between high & low tides. F organisms adapted to pounding waves & varying degrees of desiccation F low productivity Coral Reef - underwater deposits of calcium carbonate formed by colonies of animals. F very productive F high biodiversity F very fragile

] Ocean Ecosystem F covers 71% of Earth’s surface F temperature: 35 o. F 81 o. F F sunlight quickly dissipates with depth F primary producers are photoautotrophs (found near surface) & chemoautotrophs (found in deep-sea hydrothermal vents) F highest productivity near upwellings (occurs on western side of continents)