Chapter 4 Terrestrial Biomes & Aquatic Ecosystems.

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Chapter 4 Terrestrial Biomes & Aquatic Ecosystems
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Transcript of Chapter 4 Terrestrial Biomes & Aquatic Ecosystems.

  • Chapter 4Terrestrial Biomes & Aquatic Ecosystems

  • Terrestrial biomesNamed for predominant vegetationAlso have characteristic animals

  • Boundaries?No sharp boundaries between biomesIntergrades

  • Importance of climatePrevailing climate is most important factor in determining what kind of biome will developPrecipitation, temperature are most important

  • Desert biomes
  • Grassland biomes10-30 inches (25.4-76.2 cm) of rain per yearTundraTemperate grasslandTropical savanna

  • Forest biomes>30 inches (>76.2 cm) of rain per yearTaiga or coniferous forestTemperature deciduous forestTropical rain forest

  • Aquatic ecosystemsInitial categories based on salinity


  • Freshwater - nonmovingStanding watersLakesPondsSignificant stratification in community structureLightTemperature

  • Freshwater - movingMoving watersRiversStreamsCommunities change from headwaters (source) to mouth as environment changes

  • Headwaters vs. mouthHeadwatersCoolHigh current velocitiesFew nutrientsMouthWarmerSlowerMore turbidMore nutrients

  • MarineVertical and horizontal changesLightTemperatureNearshoreOpen ocean

  • EstuaryFreshwater rivers merge with oceansMixing zoneVery high productivityThreatened by pollution

  • Climatograph

  • ClimographTemperature, precipitation not sole determinersOverlap among different biomes on plot suggests that other factors also are importantSeasonality of precipitationTemperature fluctuations around meanSoil composition (based on geology)

  • DesertsLands where evaporation exceeds rainfallHigh evaporation rate7-50X precipitation

  • DesertsOccur in 2 distinct belts between 15-35 N & S latitudeResult primarily from worldwide circulation of air masses (dry over deserts)~25% of worlds land mass

  • True deserts
  • Desert lifePlants, animals are either drought evaders or drought resistors

  • EvadersPlants survive dry periods as seeds, but germinate, grow, and reproduce after rainfallAnimals may hibernate (cold) or estivate (hot)Dormancy during dry periodE.g., spadefoot toad emerges to reproduce in pools formed after rain

    E.g., birds migrate in and out

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

  • Resistors - animalsBehavioral adaptationsCome out only at night - spiders, scorpions, rodents, predators

  • Resistors - animalsPhysiological adaptationsNo need to drinkKangaroo rate with super kidneys gets all water from seeds

  • GrasslandsTropical savannas - grasslands with scattered individuals treesCentral S. Amer., Central & S. Africa

  • Savannas3 distinct seasonsCool-dry, hot-dry, warm-wetFrequent fires suppress trees, maintain grasses and forbsHerbaceous, low-growing annuals & perennials (dicots)Regrow from roots or seeds every year

  • SavannasLarge herbivores (zebras, giraffes) and burrowing animals most commonMost active during the rainy season

  • Temperate grasslandsSimilar to tropical savanna, but occur in cooler regionsN. Amer. prairie (French for plains)Russian steppeHungarian pusztasS. Amer. pampasAfrican veldt

  • Temperate grasslandsAt one time covered 42% of world land surfaceMuch under cultivation todayExcellent soilsRich topsoil layer

  • Temperate grassland climateHigh rates of evaporationPeriodic severe droughtRainfall ~25-75 cm/yearToo light to support forest, but too heavy to encourage desert

  • Temperate grassland grassesSod-formingKentucky bluegrassBunch grassesBig, little bluestem

  • Temperate grasslandsMost require periodic fires for maintenance, renewal, elimination of incoming/invading woody growthAnimal life dominated by grazing and burrowing species

  • TundraNorthernmost limits for plant growth, and at high altitudesPlants generally low-growingMat or shrubby

  • Arctic tundraEncircles north pole

    Brief warm summers with nearly 24 hrs of sun/dayPresence of permafrostWater-logged soils - low evaporationShrubs, sedges grasses, mosses, lichens

  • Alpine tundraAt high elevations at all latitudesVariable daylength, many of the same restrictions, plant species

  • Tundra animalsMigratory, well-suited for cold climateMusk oxen, caribou, reindeerLemmings, white fox, snowy owl

  • Tropical forestsEquatorial, mean temp. ~25C, 12 hrs sunlight per dayRainfall highly variable-determines type of tropical forest present

  • Types of tropical forestsThorn forests - furthest from equator, prolonged dry season

  • Types of tropical forestsTropical deciduous forestMore rainfall nearer equator, distinct wet, dry seasonsLose leaves during dry seasons

  • Types of tropical forestsTropical rain forest>250 cm of rain per yearPerpetual midsummer conditionsUninterrupted plant growth

  • Tropical rain forestsContain as many species of plants and animals as all other types of ecosystems combined4 mi2 area - 750 species of trees, 1500 species of flowering plants

  • Tropical rain forestsTypically stratified into 5 layers

    Each layer has characteristic plants, animalsMay reach height of 80 m

  • Tropical rain forest soilVery poor - little or no topsoilEasily weatheredSubsoil with iron-based clay - lateriteMajor problems with slash-and-burn agriculture

  • Tropical rain forests todayDeforestation

  • DeforestationLoss of forests at present rate will mean disappearance within next 15-25 yearsMajor problems will result from climate change, loss of species of medicinal, economic importance

  • Temperate deciduous forestEastern N. Amer, N. Europe and eastModerate temps., moderate moisture levels5-6-month growing season

  • Temperate deciduous forestDominated by broad-leaved deciduous treesRelatively nutrient-rich soil provides for good growthTypically have 4 layers presentGround, shrub, sapling, canopyRich diversity of plant, animal life

  • TaigaBoreal forest, coniferous forest

    Harsh winters with lots of snow

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

    Best suited for short growing season because they are not deciduousCan carry out photosynthesis whenever temps. rise above freezingNeedle shape, waxy cuticle conserve moisture

  • Taiga soilsThin, acidic, develop slowlyPine needles break down slowly in cool climate

  • Taiga animalsPrimarily seed, insect eaters, or those that feed on plants in or near waterSquirrels, birds, elk, moose, deer, beaver, porcupine, grizzlies, wolves

  • Standing freshwatersLakes and ponds

  • Standing freshwatersSignificant stratification in community structureLightPhotic zonePhytoplankton, zooplanktonAphotic zoneDetritus, decomposers

  • Moving freshwatersLongitudinal zonation in physical, chemical characteristics

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

  • Marine3/4 of worlds surface, major impact on climate, wind patterns, algae supply most of worlds oxygen

  • Marine

  • MarinePhotic, aphotic zones (vertical)Intertidal, neritic, oceanic zones (horiz.)Intertidal-wetted, dried from tidesNeritic-shallow regions over continental shelvesOceanic-beyond shelves - deep zonesPelagic-open waterBenthic-sea floorAbyssal zone-deep benthic - cold, high water pressure, no light

  • Deep sea fishes

  • EstuaryFreshwater rivers merge with oceans

  • EstuaryNot very diverse - few species tolerant of salinityVery productive - oysters, crabs, fish, waterfowlMost in danger from water pollution