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Biomes and Global Ecology Chapter 48 PHYSICAL BASIS OF CLIMATE 48.1 Solar radiation, wind and ocean currents, and topography determine the distribution of major climatic zones on Earth. • Climate: long-term average weather. Determined by: – Solar radiation – Global patterns of wind and ocean circulation – Earth’s varying topography SOLAR RADIATION • Major determinant of Earth’s surface temperature: the angle at which solar radiation strikes the surface. • Earth climate: hot near the equator and cold at the poles; this reflects incoming solar radiation. • Sunlight strikes equatorial regions directly, but at higher latitudes, Earth’s surface is tilted at an angle to incoming radiation. • At higher latitudes, temperature is not only lower, it also exhibits greater variation through the year. • Seasonality: reflects a second feature of Earth – Earth’s axis of rotation is not oriented perpendicular to incoming sunlight but rather tilts at an angle of 23.5 degrees – This is why most parts of globe show seasonal variation of temperature. Climate The latitudinal difference in incoming solar energy density explains why Earth’s surface is hotter at the equator and cools towards the poles. North pole At the equator, solar energy strikes Earth directly, resulting in high influx of energy per unit area. 60˚ 30˚ ~1000 km 0˚ Solar radiation 30˚ 60˚ South pole ~2000 km At high latitude, incoming solar energy strikes Earth at an angle, resulting in lower fluxes of energy per unit area. Annual Mean Temperature TOPOGRAPHY • Wind and ocean currents transport heat from equator toward poles • Topography: physical features of earth – Also contributes to global temperature patterns – Mountaintops: can be glaciated, even at low latitudes • Temperature declines with increasing elevation – Mountains show a pattern in which climate and biomes change as elevation increases Rising and descending air organizes the atmosphere into a series of cells from the equator to the poles. 90˚ N 60˚ N 30˚ N Easterlies Westerlies Trade winds 0˚ Equator Trade winds 30˚ S Westerlies 60˚ S Easterlies 90˚ S High temperatures warm air near the equator. Because of its lower density, the warm air rises. Cool air Sun Warm air Hadley cell Equator As air rises and spreads outward toward the poles, it cools, eventually becoming dense enough to sink back to the surface. Coriolis Effect B Equator A B Equator A As Earth rotates on its axis, a point on the equator moves a greater distance per time unit than points at higher latitudes. On a rotating globe, a point traveling north will also travel east. Because of Earth’s counterclockwise rotation , winds in No. Hemisphere deflect to the right ; those in the So. Hemisphere deflect to the left Ocean Currents North Pacific North Equatorial North Equatorial Equatorial Counter North Equatorial South Equatorial Guinea Equatorial Counter Antarctic Circumpolar Antarctic Circumpolar (West Wind Drift) Warm-water current Cold-water current Rainfall Patterns Average Annual Precipitation, 1971-2000, Washington Precipitation (inches) Cascade Range Less than 10 10-20 20-30 30-40 40-60 60-80 80-100 100-140 140-180 More than 180 As air rises over the mountain, it cools, releasing its moisture as rain. Prevailing winds Warm Pacific Ocean Rainfall Patterns Once over the mountain, the air descends, warming and taking up moisture. • Mountains can have a regional pattern on climate because of rain shadow. • Differing amounts of rain on the wind-facing and opposite sides of mountain ranges. Tundra Temperate grasslands Alpine Desert Taiga Chaparral Temperate coniferous forest Savanna Deciduous forest Tropical rain forest • Regional climate reflects the interactions among solar radiation, global patterns of circulation, and Earth’s varying topography. • Biomes, in turn, reflect these variations in climate. Evapotranspiration Biomes reflect the interaction of Earth and life Evotranspiration affected by: • Amount of annual precipitation • Sun intensity Distribution of biomes reflects regional climates Plant Convergence Convergence: cacti in deserts of North America and in Africa look similar because they most both conserve water; but they are NOT closely related BIOMES 47.2 Biomes are broad, ecologically uniform areas characterized by their climate, soil, and plant/animal species. Temperate • • • • Tundra Alpine Talga Temperate Coniferous Forest • Deciduous Forest Grassland Desert Chaparral Savanna Rain Forest Terrestrial Biomes • Primary producers: mainly vascular plants • Plants also provide a structure for these biomes • Primary consumers: variety of animals; mammals, insects • Secondary consumers: carnivorous vertebrates….lions, tigers, wolves Tundra • • • • • • Close to North Pole, above 65o degree N Coldest biome Permanent ice below soil Low plant diversity…mainly mosses, lichen, herbs Primary consumers: caribou, rabbits, birds Secondary consumers: wolves, foxes Alpine • • • • • Similar to tundra, but lacks permanent ice below soil Found throughout world at high altitudes (10,000 ft, but just below snow line) Windy and cold Low and slow-growing plants Primary consumers: mountain goats, llamas, yaks Taiga • • • • • Cool, moist forests at 50 -65 degree N Plants are conifers Soils deep with accumulated organic matter….acidic and poor in nutrients Primary consumers: elk, moose, caribou, porcupines Secondary consumers: bears, lynx, wolves, foxes Temperate Coniferous Forest • • • • • Occur below 50 degrees N Temperate with much precipitation North America, northern Japan, parts of Europe, and continental Asia Enormous conifers along Pacific coast of US; undergrowth is ferns Insect and vertebrate diversity : higher than taiga forests Deciduous Forest • • • • • • Across much of North America, Europe and Asia Moderate climate Hardwood deciduous trees……maples oaks, poplar, birches Human disturbance from agriculture and urban development Much organic soil Insects, birds and mammals are diverse; also snakes, lizards, and amphibians Temperate Grassland • • • • • • • Occupied most of Midwestern US prior to settlement Mainly grasses Fire maintains grass population Soils accumulate nutrients; most productive agricultural lands in the world Before colonization by humans: bison, horses, mammoths Now, burrowing grazers such as prairie dogs are common Secondary consumers: ferrets, badgers, foxes, birds of prey Desert • • • • • • • Around the world north and south of equator from 25o -35o. Windy; little precipitation Deep-rooted plants adapted to store water, i.e. cactus Primary production is low; Soils poor in nutrients, but high in salt Primary consumers tend to be small….diverse lizards, rodents Secondary consumers: snakes, coyotes, cat species, birds Chaparral • • • • • • Narrow range of climate conditions Occurs on western edge of continents from 32o-40o north and south of equator Limited rain and falls in 2-4 months Plants are annual herbs, evergreen shrubs, and small trees Drought resistant trees, fire resistant Poor nutrients in soil Savanna • • • • • • • Eastern Africa, southern South America, Australia Tall, perennial grasses Rain is seasonal Scattered trees and shrubs Animal diversity is high; Primary consumers: antelopes, zebras, giraffes, kangaroos, large rodents Secondary consumers: lions, other cat species, hyenas, wild dogs, dingoes, snakes Tropical Rain Forest • • • • • • • • Moist, highly diverse forest North and south of the equator from 10o N-10o S Very hot and heavy rains Huge tree diversity; very tall, epiphytic plants common Decomposition rapid Primary consumers: smaller primates, bats, rodents, birds, snakes, lizards Insects are especially abundant and diverse Ants make up 30% of animal biomass here Latitudinal Diversity Gradient in Mammals • Tropical biomes have more species than temperate biomes • The number of mammal species decreases from equator to the poles. • Known as Latitudinal Diversity Gradient AQUATIC BIOMES • Aquatic biomes: – reflect climate, availability of nutrients and oxygen but especially the depth to which sunlight penetrates through water. • In shallow aquatic environments such as lake margins and coastal marine settings: – much plant, algal, and animal debris accumulates in sediments, supporting luxuriant growth by bacteria. • Grazers (such as snails and fish) – feed on marginal plants and algae, while single-celled protists and microscopic animals called zooplankton consume phytoplankton that floats in the water. • Secondary consumers such as other fish or squid feed on the grazers. • Because oxygen gas dissolves in water only to a limited extent, surface waters directly beneath the atmosphere will have an O2 concentration about 20 times lower than that of the air. • This forces larger animals to be moving constantly to keep their gill systems well-oxygenated, or to live in places such as cold running streams and rocky marine coastlines where currents naturally produce well-oxygenated water. Aquatic Biomes Solar radiation Oceanic Neritic system system Well-mixed Average water depth 200m Photic zone Pelagic realm Aquatic Biomes • Only about 2.5% of water is fresh: lakes and rivers, glaciers, permafrost, groundwater in soil • 71% of Earth’s surface is seawater • Ocean is the largest biome Lakes • Range in size from tiny pools to the Great Lakes (has more than 20% of all freshwater) • From equator to about 80 degrees N • Primary producers: algae, cyanobacteria • Zooplankton (heterotrophic or detritivorous organisms drifting in aquatic biomes): small arthropods and rotifer protists • Nekton (all aquatic organisms that can swim freely and independent of currents): fish • Secondary consumers: turtles and birds Rivers • • • • Freshwater biomes characterized by moving water Primary producers: plants and large algae, phytoplankton Primary consumers: insects, fish, turtles, birds Salmon: spend lives in oceans, but swim up rivers to reproduce Intertidal Zone • • • • Lies along coastlines between high and low tides Organisms are exposed to the atmosphere on a daily basis Waves can cause mortality; so algae and animals securely attached to substrate Consumers: sea stars, sea urchins, mollusks, barnacles, corals Coral Reefs • Best known reefs occur in shallow, tropical to subtropical saltwater environments with little water movement • Primary production: dinoflagellate algae that live within tissues of corals • Free-living algae occur in reefs, but kept low by grazing fish • Many species invertebrates also live in coral heads • Fish diversity especially high • Coral reefs also occur in deep sea, but build gradually since coral growth is slow in absence of symbiotic algae Pelagic Realm • The part of the ocean neither close to shore nor close to seafloor: forms bulk of ocean • Organisms live within the water column: either as zooplankton (tiny arthropods)or nekton(cephalopods) • Upper region with sunlight: primary producers are diverse algae and cyanobacteria • Secondary consumers: fish, squids , heterotrophic protists Deep Sea • • • • • The deep seawaters: cold and dark High species diversity Primary producers: chemosynthetic bacteria Primary consumers: bacteria, archeons; sinking detritus Dense animal populations occur on deep seafloor in location of hydrothermal vents GLOBAL ECOLOGY 48.3 Biologically driven cycles of carbon and other essential elements shape ecology and reflect evolution. • Biogeochemical cycles: cycles of carbon and other biologically important elements as they link organisms and their environments Carbon Cycle CO2 Photosynthesis Aerobic respiration Grazing Primary producers: Autotrophs that fix CO2 into organic carbon. Primary consumers: Heterotrophs that feed on primary producers. Aerobic respiration Secondary consumers: Heterotroph s that feed on primary consumers. Predation Decomposers: Largely fungi and bacteria in soil that feed on organic detritus. Aerobic respiration Anaerobic respiration Fermentation Ecology and biogeochemical cycling are interrelated processes Nitrogen Cycle Consumers obtain N from their food. N2 Nitrogen fixation converts N2 to a form that can be used by plants. Primary producers assimilate biologically usable N from soil or symbiotic N-fixing bacteria. Denitrification Assimilation NO3– Anammox Chemoautotrophic bacteria gain the energy needed to fix nitrogen by oxidizing NH3, using O2 (nitrification) or NO2– (anammox). • • • • Nitrogen fixation Nitrification In anoxic environments, some decomposing bacteria use NO3– in respiration, a process called denitrification because it converts biologically usable N back to N2. NO2– Ammonification Nitrification NH3 N and Ph limit primary production in most biomes N in atmosphere is fixed by bacteria and archeons Then cycles thru primary consumers and decomposers Closely linked to C cycle Decomposers return N to soil as ammonia. Phosphorous Cycle Primary producers assimilate PO43– from soil. PO43 – in rock s Weatherin g Consumers get PO43– from their food. Runoff Tectonic uplift Decomposers release PO43– to soil; some is reincorporated by primary producers, some is leached. In shallow oceans PO43– is cycled rapidly among primary producers, consumers, and decomposers. Photic zone Upwelling Deep ocean Sedimentati on Ph found mainly in rocks Enters food web as phosphate ion by chemical weathering Then cycles thru ecosystems, supporting primary production GLOBAL BIODIVERSITY 48.3 Global patterns of biological diversity reflect climate, history, and ecological interactions among species. • Latitudinal Diversity Gradient: species diversity declines from equator toward poles • Earth’s biomes: historical outcome of environmental change and natural selection Mammal Global Biodiversity Tropical regions have a great diversity of different kinds of mammal, representing all of the major groups from anteaters to apes. Number of mammal species There are few mammal species near the poles, mostly rodents and their carnivore predators, plus seals and whales in the sea. Biodiversity Hotspots Tropical regions have a great diversity of different kinds of mammal, representing all of the major groups from anteaters to apes. Number of mammal species There are few mammal species near the poles, mostly rodents and their carnivore predators, plus seals and whales in the sea.