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Chapter 4. Terrestrial Biomes & Aquatic Ecosystems. Terrestrial biomes. Named for predominant vegetation Also have characteristic animals. Boundaries?. No sharp boundaries between biomes Intergrades. Importance of climate.

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Chapter 4 l.jpg

Chapter 4

Terrestrial Biomes & Aquatic Ecosystems


Terrestrial biomes l.jpg
Terrestrial biomes

  • Named for predominant vegetation

  • Also have characteristic animals


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Boundaries?

  • No sharp boundaries between biomes

  • Intergrades


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Importance of climate

  • Prevailing climate is most important factor in determining what kind of biome will develop

    • Precipitation, temperature are most important


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Desert biomes

  • <10 inches (<25.4 cm) of rain per year

  • Cool

  • Temperate

  • Tropical


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Grassland biomes

  • 10-30 inches (25.4-76.2 cm) of rain per year

  • Tundra

  • Temperate grassland

  • Tropical savanna


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Forest biomes

  • >30 inches (>76.2 cm) of rain per year

  • Taiga or coniferous forest

  • Temperature deciduous forest

  • Tropical rain forest


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Aquatic ecosystems

  • Initial categories based on salinity

    • Freshwater

    • Marine

    • Estuary


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Freshwater - nonmoving

  • Standing waters

    • Lakes

    • Ponds

  • Significant stratification in community structure

    • Light

    • Temperature


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Freshwater - moving

  • Moving waters

  • Rivers

  • Streams

  • Communities change from headwaters (source) to mouth as environment changes


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Headwaters vs. mouth

  • Headwaters

    • Cool

    • High current velocities

    • Few nutrients

  • Mouth

    • Warmer

    • Slower

    • More turbid

    • More nutrients


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Marine

  • Vertical and horizontal changes

    • Light

    • Temperature

    • Nearshore

    • Open ocean


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Estuary

  • Freshwater rivers merge with oceans

    • Mixing zone

  • Very high productivity

  • Threatened by pollution



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Climograph

  • Temperature, precipitation not sole determiners

  • Overlap among different biomes on plot suggests that other factors also are important

    • Seasonality of precipitation

    • Temperature fluctuations around mean

    • Soil composition (based on geology)


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Deserts

  • Lands where evaporation exceeds rainfall

  • High evaporation rate

    • 7-50X precipitation


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Deserts

  • Occur in 2 distinct belts between 15-35° N & S latitude

  • Result primarily from worldwide circulation of air masses (dry over deserts)

  • ~25% of world’s land mass


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True deserts

  • <10 inches of rain per year

    • Semi-deserts may have 2-3X that, but have high evaporation rates

  • Low humidity results in very hot days, but cool or cold nights

  • Life is keyed to rainfall events

    • Infrequent, but usually heavy when they occur


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Desert life

  • Plants, animals are either drought evaders or drought resistors


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Evaders

  • Plants survive dry periods as seeds, but germinate, grow, and reproduce after rainfall

  • Animals may hibernate (cold) or estivate (hot)

    • Dormancy during dry period

    • E.g., spadefoot toad emerges to reproduce in pools formed after rain

    • E.g., birds migrate in and out


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Resistors - plants

  • Plants develop deep roots to become independent of rainfall events (woody shrubs) or are succulents to store water in stems (cactus)


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Resistors - animals

  • Behavioral adaptations

  • Come out only at night - spiders, scorpions, rodents, predators


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Resistors - animals

  • Physiological adaptations

  • No need to drink

    • Kangaroo rate with super kidneys gets all water from seeds


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Grasslands

  • Tropical savannas - grasslands with scattered individuals trees

    • Central S. Amer., Central & S. Africa


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Savannas

  • 3 distinct seasons

  • Cool-dry, hot-dry, warm-wet

  • Frequent fires suppress trees, maintain grasses and forbs

    • Herbaceous, low-growing annuals & perennials (dicots)

    • Regrow from roots or seeds every year


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Savannas

  • Large herbivores (zebras, giraffes) and burrowing animals most common

  • Most active during the rainy season


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Temperate grasslands

  • Similar to tropical savanna, but occur in cooler regions

    • N. Amer. prairie (French for plains)

    • Russian steppe

    • Hungarian pusztas

    • S. Amer. pampas

    • African veldt


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Temperate grasslands

  • At one time covered 42% of world land surface

  • Much under cultivation today

  • Excellent soils

    • Rich topsoil layer


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Temperate grassland climate

  • High rates of evaporation

  • Periodic severe drought

  • Rainfall ~25-75 cm/year

  • Too light to support forest, but too heavy to encourage desert


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Temperate grassland grasses

  • Sod-forming

    • Kentucky bluegrass

  • Bunch grasses

    • Big, little bluestem


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Temperate grasslands

  • Most require periodic fires for maintenance, renewal, elimination of incoming/invading woody growth

  • Animal life dominated by grazing and burrowing species


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Tundra

  • Northernmost limits for plant growth, and at high altitudes

  • Plants generally low-growing

    • Mat or shrubby


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Arctic tundra

  • Encircles north pole

  • Brief warm summers with nearly 24 hrs of sun/day

  • Presence of permafrost

  • Water-logged soils - low evaporation

  • Shrubs, sedges grasses, mosses, lichens


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Alpine tundra

  • At high elevations at all latitudes

  • Variable daylength, many of the same restrictions, plant species


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Tundra animals

  • Migratory, well-suited for cold climate

    • Musk oxen, caribou, reindeer

    • Lemmings, white fox, snowy owl


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Tropical forests

  • Equatorial, mean temp. ~25°C, 12 hrs sunlight per day

  • Rainfall highly variable-determines type of tropical forest present


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Types of tropical forests

  • Thorn forests - furthest from equator, prolonged dry season


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Types of tropical forests

  • Tropical deciduous forest

  • More rainfall nearer equator, distinct wet, dry seasons

  • Lose leaves during dry seasons


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Types of tropical forests

  • Tropical rain forest

  • >250 cm of rain per year

  • Perpetual midsummer conditions

  • Uninterrupted plant growth


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Tropical rain forests

  • Contain as many species of plants and animals as all other types of ecosystems combined

  • 4 mi2 area - 750 species of trees, 1500 species of flowering plants


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Tropical rain forests

  • Typically stratified into 5 layers

  • Each layer has characteristic plants, animals

  • May reach height of 80 m


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Tropical rain forest soil

  • Very poor - little or no topsoil

  • Easily weathered

  • Subsoil with iron-based clay - laterite

  • Major problems with slash-and-burn agriculture



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Deforestation

  • Loss of forests at present rate will mean disappearance within next 15-25 years

  • Major problems will result from climate change, loss of species of medicinal, economic importance


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Temperate deciduous forest

  • Eastern N. Amer, N. Europe and east

  • Moderate temps., moderate moisture levels

    • 5-6-month growing season


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Temperate deciduous forest

  • Dominated by broad-leaved deciduous trees

  • Relatively nutrient-rich soil provides for good growth

  • Typically have 4 layers present

    • Ground, shrub, sapling, canopy

    • Rich diversity of plant, animal life


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Taiga

  • Boreal forest, coniferous forest

  • Harsh winters with lots of snow


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Taiga

  • Dominated by conifers - spruce, pine, fir, hemlock

  • Best suited for short growing season because they are not deciduous

    • Can carry out photosynthesis whenever temps. rise above freezing

    • Needle shape, waxy cuticle conserve moisture


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Taiga soils

  • Thin, acidic, develop slowly

  • Pine needles break down slowly in cool climate


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Taiga animals

  • Primarily seed, insect eaters, or those that feed on plants in or near water

  • Squirrels, birds, elk, moose, deer, beaver, porcupine, grizzlies, wolves


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Standing freshwaters

  • Lakes and ponds


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Standing freshwaters

  • Significant stratification in community structure

  • Light

    • Photic zone

      • Phytoplankton, zooplankton

    • Aphotic zone

      • Detritus, decomposers


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Moving freshwaters

  • Longitudinal zonation in physical, chemical characteristics

  • Change in producers, benthic (bottom dwelling), fish assemblages


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Marine

  • 3/4 of world’s surface, major impact on climate, wind patterns, algae supply most of world’s oxygen



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Marine

  • Photic, aphotic zones (vertical)

  • Intertidal, neritic, oceanic zones (horiz.)

    • Intertidal-wetted, dried from tides

    • Neritic-shallow regions over continental shelves

    • Oceanic-beyond shelves - deep zones

  • Pelagic-open water

  • Benthic-sea floor

    • Abyssal zone-deep benthic - cold, high water pressure, no light



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Estuary

  • Freshwater rivers merge with oceans


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Estuary

  • Not very diverse - few species tolerant of salinity

  • Very productive - oysters, crabs, fish, waterfowl

  • Most in danger from water pollution