Chapter 3 BIOMES AND AQUATIC ECOSYSTEMS

Biomes Major types of terrestrial ecosystems. Distribution of biomes 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.

Tropical Rain Forest warm & moist (rainfall: in/yr) nutrients cycle rapidly soils are nutrient poor due to water leaching plants exhibit vertical stratification very high biodiversity

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

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

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

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(rainfall: in/yr) lack trees & shrubs grazing & frequent fires maintain grass In US, majority of prairie has been replaced by farmland.

Temperate Forests rainfall: in/yr Temperate forests are either deciduous or coniferous. Temperate Deciduous Forest Trees that lose their leaves moist growing season (at least 4 months) soil rich in nutrients vertical stratification organisms adapted to seasonal changes

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

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

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)

Aquatic Ecosystems Freshwater Ecosystems Lakes and Ponds (standing water) littoral zone limnetic zone profundal zone benthic zone

Lakes and Ponds (standing water) Littoral zone - shallow area where light reaches the bottom; contains the greatest number & diversity of organisms (rooted plants, phytoplankton, zooplankton, insects, fish, reptiles). Limnetic zone - upper layer of open water; extends down as far as light reaches. Find phytoplankton, zooplankton & fishes. Profundal zone - deeper layer of open water; light does not penetrate. Find scavengers & decomposers. Benthic zone - lake bottom. Find scavengers & decomposers.

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

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

Rivers and Streams (running water) Transport rainwater, groundwater, snowmelt & sediment from land to ocean or lake. At headwaters: channel is narrow water is clear & oxygen- rich current is swift At mouth: channel widens water is murky & contains less oxygen 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. water is brackish salinity fluctuates very productive high biodiversity nursery for many ocean animals

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

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

Ocean Ecosystem covers 70% of Earth’s surface temperature: 35 o F - 81 o F sunlight quickly dissipates with depth primary producers are photoautotrophs (found near surface) & chemoautotrophs (found at deep-sea hydrothermal vents) highest productivity near upwellings (occurs on western side of continents)