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Chapter eleven
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  • 1. Title Page Photo “ In short, the animal and vegetable lines, diverging widely above, join below in a loop.” —Asa Gray (Brainyquote.com)
  • 2. Ecosystems and Biomes
    • Two organizing principles are ecosystem and biome.
    • Ecosystem: A Concept for All Scales
      • Ecosystem —the totality of interactions among organisms and the environment in the area of consideration.
        • Encompasses both the living and nonliving portion and how energy flows among them.
        • Weakness—there is an almost infinite variety in the magnitude of ecosystems that can be studied:
      • Range includes whole Earth itself to drop of water.
  • 3. Ecosystems and Biomes
    • Biome: A Scale for All Biogeographers
      • Biome—a large, recognizable assemblage of plants and animals in functional interaction with its environment.
      • Most appropriate scale for understanding world distribution patterns.
  • 4. Ecosystems and Biomes
    • Eleven major types
      • Often significant and even predictable relationships exist between the biota (particularly the flora) of a biome and the associated climate and soil types.
    • Ecotone—the transition zone between biotic communities in which the typical species of one community intermingle or interdigitate with those of another.
    Marsh/mangrove ecotone with fire, freeze, and hurricane damage. Taken September 20, 2001
  • 5. Terrestrial Flora
    • Geographers interested in natural vegetation of landscape for three reasons:
      • Plants are likely to dominate a landscape (except where terrain is rugged, climate is harsh, or humans have intervened);
      • Vegetation is a sensitive indicator of other environmental attributes;
      • Vegetation is often instrumental to human settlement and activities.
  • 6. Characteristics of Plants
    • Most very hardy.
    • High survival potential dependent on:
      • Subsurface root system
      • Reproductive mechanism
        • Perennial—plant that can live more than a single year despite seasonal climatic variations.
        • Annual—plant that perishes during times of climatic stress but leaves behind a reservoir of seeds to germinate during the next favorable period.
  • 7. Characteristics of Plants
    • Common characteristics:
      • Roots (to gather nutrients and moisture and to anchor plant);
      • Stems and branches (to support and transport nutrients);
      • Leaves (to collect solar energy, exchange gases, and transpire water);
      • Reproductive organs.
  • 8. Floristic Terminology
    • Categorizing by reproduction:
      • Through spores
        • Those that reproduce by spores are in two major groups:
          • Bryophytes—spore-bearing plants such as mosses and liverworts; never dominated in history, but can be very important in some localized situations.
          • Pteridophytes—spore-bearing plants such as ferns, horsetails, and clubmosses; used to dominate continental vegetation, but no more.
    Spores Bryophytes Pteridophytes
  • 9. Floristic Terminology
      • Through seeds
        • Those that reproduce by seeds are in two major groups:
          • Gymnosperms—seed-reproducing plants that carry their seeds in cones; also known as conifers.
            • Used to be more important, in geologic past.
          • Angiosperms—plants that have seeds encased in some sort of protective body, such as a fruit, a nut, or a seedpod.
            • Have dominated planet vegetation for last 50 million to 60 million years.
    Seeds Gymnosperms Angiosperms
  • 10.
      • Other terms
          • Fig. 11-3
    Trees Gymnosperms Angiosperms Softwood Coniferous Needleleaf Hardwood Deciduous Broadleaf
  • 11. Floristic Terminology
    • Categorizing by stem or trunk composition:
      • Woody plant—plant that has stem composed of hard fibrous material; refers mostly to trees and shrubs.
      • Herbaceous—refers to plants that have soft stems; mostly grasses, forbs, and lichens.
    • Categorizing by leaf retention:
      • Deciduous—refers to trees that experience an annual period in which all leaves die and usually fall from the tree, due either to a cold or dry season.
      • Evergreen—a tree or shrub that sheds its leaves on a sporadic or successive basis, but at any given time appears to be fully leaved.
  • 12. Floristic Terminology
    • Categorizing by leaf shape:
      • Broadleaf—tree that has flat and expansive leaves.
        • Majority are deciduous.
        • In rainy tropics, everything is evergreen.
      • Needleleaf—refers to trees adorned with thin slivers of tough, leathery, waxy needles rather than typical leaves.
        • Almost all are evergreen.
  • 13. Floristic Terminology
    • Categorizing by supposed structure—but this is unsatisfactory.
      • Hardwood—angiosperm tree that is usually broad-leaved and deciduous. Wood has a relatively complicated structure, but is not always hard.
      • Softwood —gymnosperm tree; nearly all such trees are needle-leaved evergreens with wood of simple cellular structure but not always soft.
  • 14. Environmental Adaptations
    • Two prominent adaptation strategies of plants to protect against environmental stress are
      • Xerophytic adaptations
      • Hygrophytic adaptations
  • 15. Environmental Adaptations
    • Xerophytic—refers to plants structurally adapting to withstand protracted dry conditions.
      • Roots, stems, leaves, reproductive cycle can all adapt in various ways.
    • Succulent—plant that has fleshy stem that stores water.
  • 16. Environmental Adaptations
    • Hygrophytic—refers to plants structurally adapting to withstand protracted wet conditions.
    • Hygrophytic Adapatation
      • Hygrophyte—plant that requires a saturated or semi-saturated environment (frequent soakings with water).
  • 17. Environmental Adaptations
    • Likely to have extensive root system for anchoring in soft ground.
    • Usually relies on buoyancy of water for support rather than stem.
    • Many have weak, pliable stems so can withstand currents.
    • Hydrophytes are often grouped in with this category.
      • Hydrophyte—a “water-loving” plant that is adapted to live in more or less permanently immersed in water.
  • 18. Environmental Adaptations
    • Hygrophytic Adapatation
      • Hygrophyte—plant that requires a saturated or semi-saturated environment (frequent soakings with water).
      • Likely to have extensive root system for anchoring in soft ground.
      • Usually relies on buoyancy of water for support rather than stem.
      • Many have weak, pliable stems so can withstand currents.
    • Hydrophytes are often grouped in with this category.
      • Hydrophyte—a “water-loving” plant that is adapted to live in more or less permanently immersed in water.
  • 19. The Critical Role of Competition
    • Competition is key in which plants grow where.
      • Even though all conditions (climatic, edaphic, etc.) are favorable, a plant may not take hold in one area because of competition.
    Kudzu Vine
  • 20. Spatial Groupings of Plants
    • Geographers usually more concerned with spatial groupings than individual plants.
      • Groups based on dominant members, dominant appearance, or both.
  • 21. Spatial Groupings of Plants
    • Floristic pattern of Earth is impermanent.
    • Change can be slow and orderly, as in lake infilling.
    • Change can be abrupt and chaotic, as in wildfire.
      • Climax vegetation—a stable plant association of relatively constant composition that develops at the end of a long succession of changes.
  • 22. Spatial Groupings of Plants
    • Is an association in equilibrium with prevailing environmental conditions.
    • Should persist until environmental disturbance/change occurs.
    • Seral association—various stages leading up to climax vegetation.
  • 23. Spatial Groupings of Plants
    • Geographers can face significant difficulties in recognizing spatial groupings.
    • As one tries to identify patterns and recognize relationships, must make generalizations.
      • When associations are portrayed on maps, boundaries usually represent approximations.
      • Human interference plays a major role.
      • Because of human impact, climax vegetation is now the exception rather than rule.
    • Maps often ignore human interference, so are actually maps of theoretical natural vegetation.
  • 24. Spatial Groupings of Plants
    • Many ways to classify plant associations.
      • Geographers usually place emphasis on structure and appearance of dominant plants.
      • Major associations include forests, woodlands, shrublands, grasslands, deserts, tundra, and wetlands.
  • 25.
          • Fig. 11-7
  • 26. Spatial Groupings of Plants
    • Forest—an assemblage of trees growing closely together so that their individual leaf canopies generally overlap.
      • Likely to become climax association in any area where moisture is adequate and growing season isn’t very short.
    • Woodland—tree-dominated association in which the trees are spaced more widely apart than those of forests and do not have interlacing canopies.
    • Shrubland —plant association dominated by relatively short woody plants.
      • Wide latitudinal range but usually restricted to semiarid or arid areas.
  • 27. Spatial Groupings of Plants
    • Grassland—plant association dominated by grasses and forbs.
      • Prominent types are savanna, prairie, and steppe.
      • Associated with semiarid and subhumid climates.
    • Desert—actually a climate, not an association per se, but is typified by plants widely scattered on bare ground.
    • Tundra—a complex mix of very low-growing plants, including grasses, forbs, dwarf shrubs, mosses, and lichens, but no trees.
      • Only in the perennially cold climates of high latitudes or high altitudes.
  • 28. Spatial Groupings of Plants
    • Wetland—landscape characterized by shallow, standing water all or most of the year, with vegetation rising above the water level.
      • Have much more limited geographic extent than any other above associations.
    Carson River, NV
  • 29. Spatial Groupings of Plants
    • Various plant associations will exist in relatively narrow zones when mountain slopes have significant elevational changes in short horizontal distances.
      • Vertical zonation—the horizontal layering of different plant associations on a mountainside or hillside.
        • Elevation changes are counterpart of latitude changes.
        • Treeline elevation varies with latitude.
        • Southern and Northern hemispheres experience different elevation–latitude relationship, with Southern Hemisphere having lower treelines.
        • Reason for discrepancy is not understood yet.
    • Can have significant local variations caused by a variety of local environmental conditions.
  • 30.
          • Fig. 11-10
      • Vertical Zonation
        • Most apparent in mountains due to changes in elevations over short distances
  • 31. Spatial Groupings of Plants
    • Exposure to sunlight is often a critical determinant of vegetation composition.
      • Adret slope—Sun slope; slope where Sun’s rays arrive at a relatively direct angle.
        • Relatively hot and dry, and its vegetation is sparser and smaller than that on adjacent slopes with different exposures.
        • Likely to have species composition different from adjacent slopes.
      • Ubac slope—a slope where sunlight strikes at a low angle and hence is much less effective in heating and evaporating than on the adret slope, thus producing more luxuriant vegetation of a richer diversity.
        • Difference between adret and ubac decreases with increasing latitude.
        • Valley-bottom locations can have vegetation composition significantly different from slopes running to it.
  • 32.
      • Local Variations
        • Exposure to sunlight
          • Mountainous landscapes
          • Fig. 11-13
  • 33.
      • Local Variation (continued)
        • Valley-bottom location
          • Fig. 11-14
  • 34. Spatial Groupings of Plants
    • Riparian vegetation—streamside growth, particularly prominent in relatively dry regions, where stream courses may be lined with trees, although no other trees are to be found in the landscape.
  • 35. Terrestrial Fauna
    • Animals occur in much greater variety than plants over Earth.
    • Animals, however, tend to be much less prominent than plants in the landscape.
    • They tend to be secretive and inconspicuous.
    • Also, environmental relationships are much less clearly evidenced by animals than plants.
    • Their inconspicuousness makes it more difficult to study them, and their mobility had lead to greater environmental adaptability among them.
  • 36. Characteristics of Animals
    • Variety of animal life is so great that it is difficult to find many unifying characteristics.
      • Two universal traits (though these aren’t always immediately recognizable):
        • Mobility
        • Need to eat plants and/or other animals
    The tree of life at Animal Kingdom 
  • 37.
    • Characteristics of Animals
      • Great diversity
      • Two universal features
        • Motile
        • Heterotrophs
          • Consumers (incapable of manufacturing food from air, water and sunlight like plants do)
          • Fig. 11-15, 16, 19a, 21, & 27
  • 38. Kinds of Animals
    • Size and habits are not valid indicators of animal’s significance to geographic study.
    • Minute and seemingly inconsequential organisms can play important roles.
    • Examples are carriers of disease, providers of scarce nutrients.
    • More than 90% of all animal species are invertebrates (without backbones).
    • Arthropods most prominent (insects, spiders, centipedes, millipedes, crustaceans).
    • Five groups of vertebrates, those with backbone:
      • Fish, amphibians, reptiles, birds, and mammals.
  • 39.
    • Kinds of Animals
      • Invertebrates
      • Vertebrates
        • Fishes
        • Amphibians
        • Reptiles
        • Birds
        • Mammals
          • Fig. 11-15, 16, 19a, 21, 27 & 11-17
  • 40. Kinds of Animals
    • Most mammals are placentals, having young grow and develop in mother’s body.
      • About 135 species are marsupials, in which mothers carry young, not fully developed at birth, in pouches.
      • Two species are monotremes—lay eggs.
        • Echidna and duckbill platypus.
  • 41. Environmental Adaptations
    • Three different kinds of evolutionary adaptation by animals:
      • Physiological
      • Behavioral
      • Reproductive
  • 42. Example of Animal Adaptations to Desert Life
    • Faunal diversity can be astounding in desert areas where water is permanent or prolonged.
    • Even in areas where open water is not available, there are pockets of localized favorable habitat that permit remnant populations to survive.
    • Most animals are completely nocturnal.
    • Animals are more conspicuous when cooler, such as at night and winter.
    • Some animals follow rains in nomadic fashion.
    • Most prominently displayed by birds.
  • 43. Example of Animal Adaptations to Desert Life
    • Some spend significant time underground.
    • Some bury selves to survive long dry spells, such as freshwater crayfish and crabs.
    • Text provides detailed discussion of anatomical and physiological adaptations.
    • A few species of rodents can exist from birth to death without ever taking a drink.
    • Get moisture from food.
    • Some species display ability to delay reproductive processes over long dry periods until more favorable conditions occur.
    • Australian desert kangaroos can delay implantation of fertilized blastocyst, so it remains in inactive state in uterus until better weather conditions occur.
  • 44. Competition Among Animals
    • Competition can be both direct and indirect.
    • Indirect—rivalry for space and resources.
    • Direct—antagonism of predation.
    • Many create social groups among own species.
  • 45. Competition Among Animals
    • Some across species, such as communal relationship among zebras, wildebeest and impalas in East African savannas.
    • Individual animals are concerned either largely or entirely with own survival.
    • Some animal species concerned with survival of mates.
    • Some concerned with survival of young (more common as maternal instinct, though some paternal too).
    • Still fewer concerned with survival for group.
  • 46. Cooperation among Animals
    • Symbiosis—association of two dissimilar organisms, in which they live together in some fashion.
    • Mutualism—symbiotic relationship in which the association is mutually beneficial to both organisms.
    • Commensalism—symbiotic relationship in which the association is neither beneficial nor injurious to either.
    • Parasitism—symbiotic relationship, in which the association benefits one, but harms the other; that is, one lives on or in the other, to detriment of the host.
    Symbiosis Mutualism Commensalism Parasitism
  • 47. Zoogeographic Regions
    • Animals’ distribution patterns more complex and irregular because of their mobility.
    • The broad distributions of animals nevertheless do reflect a general distribution of energy and food diversity.
  • 48. Zoogeographic Regions
    • Nine zoogeographic regions are generally recognized.
    • Represent average conditions and cannot portray some common pattern in which different groups of animals fit precisely.
    • Map on page 329.
  • 49.
    • Zoogeographic Regions
    • Reflective of the general distribution of energy and richness of food chemistry
          • Fig. 11-23
  • 50. Zoogeographic Regions
    • Ethiopian Region
      • Has most diverse vertebrate fauna and greatest number of mammalian families.
    • Oriental Region
      • Similar to Ethiopian but with less diversity (save for birds and reptiles; large number of venomous snakes).
    • Palearctic Region
      • Poorer fauna than previous two;
      • Probably function of higher latitudes and more rigorous climate.
  • 51.
    • Palearctic Region
      • Separated from rest of Eurasia by mountains
      • Few endemic species, fewer species than in tropics
          • Fig. 11-23
  • 52.
    • Nearctic Region
      • Non-tropical portions of North America
      • Similar to Palearctic due to Bering land bridge
          • Fig. 11-23
  • 53. Zoogeographic Regions
    • Nearctic Region
      • Faunal assemblage relatively poor (save for being well-represented with reptiles).
      • Largely a transitional zone between Palearctic and Neotropical groups.
      • Great similarity to Palearctic, so that some group together into superregion, Holoarctic.
      • Reflects how faunal dispersal occurred via Bering land bridge in geologic past.
    • Neotropical Region
      • Has rich and distinctive faunal assemblage:
      • Variety of habitats and isolation from other regions;
      • Has a larger number of endemic mammal families than any other region;
      • Bird fauna is exceedingly diverse and conspicuous.
  • 54. Zoogeographic Regions
    • Madagascar Region
      • Dominated by relic assemblage of unusual forms.
      • Primitive primates (lemurs).
    • New Zealand region
      • Fauna dominated by birds (mostly flightless).
      • Almost no terrestrial vertebrates.
      • No mammals and only a few reptiles and amphibians.
  • 55. Zoogeographic Regions
    • Pacific Islands Region
      • Limited faunal assemblage.
    • Australian Region
      • Has most distinctive fauna of any region.
      • Lack of variety is made up by animals’ uniqueness.
      • The Unique Biota of Australia
      • More than 90% of the native tree species in Australia are of the single genus, Eucalyptus.
        • Above should either be “a single genus, Euc” or “the single genus Euc” (no comma)
      • These trees, which there are greater than 400 species of, are native only to Australia.
      • The shrubs and bushes of Australia are dominated by a single genus, Acacia.
      • The dominance of this genus is attributed to isolation.
  • 56.
      • Australia Region
        • Australia and adjacent islands
        • Most distinctive fauna of any region due to the region’s lengthy isolation
          • Few placental mammals
        • Its unique biota are also primarily a result of isolation
          • Fig. 11-17: Kangaroo. Fig. 11-18: Monotremes (egg-laying mammals) Echidna and duckbill platypus.
  • 57. Zoogeographic Regions
    • Australian fauna is also unique because of isolation.
      • Australian fauna is dominated by a single primitive mammalian order, marsupials.
      • The continent is also the only home to the primitive monotremes.
      • Marsupials and monotremes were able to flourish in relative isolation from competitive and predatory pressures that influenced animal evolution in other parts of the world.
      • As such, indigenous placental mammals are lacking on the continent.
  • 58. The Major Biomes
    • Named for dominant vegetation, but encompasses fauna as well as interrelationships with soil, climate, and topography.
  • 59.
    • Major Biomes
    • Summary of each biome follows…
      • Distribution (map)
      • Climate types
      • Main vegetation types
      • Limiting factors to flora and fauna
          • Fig. 11-25
          • (left panel, p. 330)
  • 60.
          • Fig. 11-25 (right panel, p. 331)
  • 61. The Major Biomes
    • Tropical Rainforest
      • Selva — tropical rainforest; a distinctive assemblage of tropical vegetation that is dominated by a great variety of tall, high-crowned trees.
        • Probably most complex of all terrestrial ecosystems.
      • Distribution closely related to climate.
      • Consistent rainfall and relatively high temperatures.
      • Layered structure, with second layer being a branch canopy formed by the high trees that crest above the canopy.
      • Undergrowth relatively sparse because of lack of light.
      • Interior is region of heavy shade, high humidity, windless air, continuous warmth, aroma of mold and decomposition.
      • Fauna is largely arboreal—tree dwelling.
      • Canopy serves as principal food source.
  • 62. The Major Biomes
    • Tropical Deciduous Forest
      • Not closely correlated with specific climatic types; distribution more irregular and fragmented.
      • Compared to rainforest, canopy is less dense, trees are shorter, and there is less diversity of tree species (but greater variety of shrubs and other lesser plants).
      • Response to either less total precipitation or less periodic precipitation.
      • Many trees shed leaves at same time, so more sunlight can penetrate.
      • Produces classic jungle conditions.
  • 63. The Major Biomes
    • Tropical Scrub
      • Widespread in drier portions of A climatic realm (covers extensive areas in tropics and subtropics).
      • Dominated by low-growing scraggly trees and tall bushes, usually with extensive understory of grasses.
      • Plant species diversity less than that in tropical rainforest and tropical deciduous.
      • Faunal diversity very different from tropical rainforest and tropical deciduous.
      • Moderately rich assemblage of ground-dwelling mammals and reptiles, and of birds and insects.
  • 64. The Major Biomes
    • Tropical Savanna
      • Distribution of biome doesn’t exactly correlate with distribution of tropical savanna climate.
      • Incomplete correlation most noticeable where seasonal rainfall contrasts are greatest (which is associated with annual shifting of the intertropical convergence zone [ITCZ]).
      • Dominated by tall grasses.
      • Some regions actually former tropical deciduous forest and even tropical rainforest, but humans converted it through fires and by grazing domestic animals.
      • Has a very pronounced seasonal rhythm: wet season, dry season, and wildfire season.
      • Savanna fauna varies according to continent.
      • Africa has most remarkable, diverse large wildlife.
      • Latin America has only sparse population of large wildlife.
  • 65. The Major Biomes
    • Desert
      • Occurs extensively in midlatitude locations in Asia, North America, and South America with a fairly close correlation to Bwh and Bwk climates.
      • Vegetation surprisingly variable.
      • Shrubs are typical, with succulents common in drier parts.
      • Trees can be found, particularly in Australia.
      • Most deserts have moderately diverse faunal assemblage.
      • Variety of large mammals is limited.
  • 66. The Major Biomes
    • Mediterranean Woodland and Shrub
      • Six widely scattered and relatively small areas in midlatitudes.
      • Have pronounced dry-summer wet-winter precipitation.
      • Dominant vegetation associations are physically similar, but taxonomically quite varied.
      • Dominated by dense growth of woody shrubs, but also have open grassy woodlands.
      • Plant species vary from region to region, but in all, the trees and shrubs are primarily broadleaf evergreens.
      • Many plants are adapted to rapid recovery after wildfire.
      • Fauna not particularly distinctive.
      • Seed-eating, burrowing rodents common.
      • General overlap of animals between this biome and adjacent ones.
  • 67. The Major Biomes
    • Midlatitude Grassland
      • Locational coincidence between this biome and steppe climatic type is very pronounced in Northern Hemisphere.
      • Less distinct climatic correlations in Southern Hemisphere.
      • Occurs widely in midlatitudes of North America and Eurasia.
      • Low precipitation and/or frequency of fire prevent growth of tree or shrub seedlings.
      • Characteristics of grasses depends on moisture: taller in wetter area (prairie), shorter in dryer (steppe), and sometimes not continuous, but grow in discrete tufts.
      • Before human encroachment, fauna comprised of large numbers of relatively few species, with migratory larger herbivores.
  • 68. The Major Biomes
    • Midlatitude Deciduous Forest
      • Used to be far more extensive in all Northern Hemisphere continents and to some extent in tracts in Southern Hemisphere.
      • Humans have cleared away large portions for agriculture.
      • Fairly dense growth of tall broadleaf trees with complete canopy in summer.
      • Winter very different, with seasonal fall of leaves.
      • Tree species vary greatly from region to region.
      • Generally has the richest assemblage of fauna in midlatitudes.
      • Seasonal variation to fauna (hibernation and migration).
  • 69. The Major Biomes
    • Boreal Forest
      • An extensive needleleaf forest in subarctic regions of North America and Eurasia; also called taiga.
      • One of most extensive biomes, occupying vast expanse of northern North America and Eurasia.
      • Close correlation with subarctic climatic type.
      • Has perhaps simplest assemblage of plants.
      • Most trees are conifers, though in some places deciduous trees interrupt the coniferous cover.
      • Trees become spindlier, short, and openly spaced in north.
      • Bogs and swamps numerous because of permanently frozen subsoil and derangement of normal surface drainage from past glaciers.
      • Faunal diversity limited because of limited food supply.
      • Populations of some species can fluctuate enormously in space of year or so.
      • Insects absent in winter but superabundant in brief summer.
  • 70. The Major Biomes
    • Tundra
      • Distribution along northern edge of Northern Hemisphere continents.
      • Essentially a cold desert or grassland.
      • No trees, but considerable mixture of species (grasses, mosses, lichens, flowering herbs, and a scattering of low shrubs).
      • Dominant animal life consists of bird and insects during summer.
      • Few species of mammals and freshwater fishes and almost no reptiles or amphibians.
  • 71. The Major Biomes
    • Alpine Tundra
      • Found in many high-elevation regions.
      • Above timberline there is sparse vegetation cover, consisting mostly of herbaceous plants, grasses, and low shrubs.
  • 72. Human Modification of Natural Distribution Patterns
    • Human activities severely alter natural distribution patterns of biota.
    • Humans directly influence biotic distributions in three ways:
      • Physical removal of organisms
      • Habitat modification
      • Artificial translocation of organisms
  • 73. Physical Removal of Organisms
    • Humans severely modify landscape, affecting both plants and animal inhabitants.
    • Cut down, plow up, pave over, burn out, poison, shoot, trap, otherwise eradicate.
          • Fig. 11-41. Central America – one of highest rates of deforestation (due mainly to expansion of cattle ranching)
  • 74. Habitat Modification
    • Humans affect native plants and animals by changing their habitat.
    • Humans change soil environment through farming, grazing, engineering, and construction.
    • Humans degrade atmospheric environment through pollution.
    • Humans impound, divert, and pollute waters.
        • Removal for agriculture often
        • results in soil erosion and
        • low crop yields as well as
        • wildlife habitat destruction.
  • 75. Tropical Rainforest Removal
    • One of Earth’s most serious environmental problems, as of last decade or so.
    • Rate of deforestation = 51 acres (21 hectares) per minute.
    • More than half of original African rainforest is now gone, about 45% of Asia’s and close to 40% of Latin America’s.
    • Current situation varies in five major rainforest regions.
    • In mid-1980s, extinction rates = about 1 species per day.
    • In mid 1990s, extinction rates = about 2 species per hour.
  • 76. Tropical Rainforest Removal
    • Loss of forest also contributes to:
      • Accelerated soil erosion
      • Drought
      • Flooding
      • Water-quality degradation
      • Declining agricultural productivity
      • Greater poverty for rural inhabitants
      • Increasing atmospheric carbon dioxide (greenhouse effect).
      • Anticipated economic benefits are usually illusory.
  • 77. Tropical Rainforest Removal
    • Continuous heavy (and expensive) fertilization necessary for sustainable agriculture.
    • Losing potential valuable resources—pharmaceutical products, new food crops, natural insecticides, industrial material, and crop hybridizations (for resisting disease, insects, parasites, and other environmental stresses).
    • Development of agroforestry (the planting of crops with trees) to counteract some of the destruction.
    • UNESCO project to set aside reserves to protect biodiversity.
    • At present about 300 preserves have been established in more than 75 countries, encompassing 12 million hectares.
    • Artificial Translocation of Organisms
  • 78. Tropical Rainforest Removal
    • Humans have introduced many wild plants and animals into “new” habitats.
    • Exotic species—organism that is introduced into “new” habitats in which it did not naturally occur.
    • Sometimes deliberate, sometimes accidental.
    • Exotics have had great impacts (cats on flightless bird populations in New Zealand, European flea in all parts of world).
    Walking Catfish, Florida
  • 79. Biotic Rearrangement: The Sad Case of Florida
    • Human actions in introducing exotic (nonnative) species result in usually one of two extremes:
    • Either exotic dies out in a short time; or
    • It flourishes extraordinarily.
    • When flourishes, can occasionally have a salutary effect, but many cases either unsatisfactory or absolutely disastrous.
  • 80. Biotic Rearrangement: The Sad Case of Florida
    • Florida presents perhaps the most frightening case study.
    • In last decade or so, state has experienced one of highest in-migration of people anywhere.
    • Has created massive disruptions in ecosystems, and exotics are most likely to prosper when ecosystem is unstable.
    • Artificial drainage provides routes for easy dispersal of aquatic organisms.
    • Has become the major world center for animal-import industry.
    • Has become almost as important in plant import industry.
    • Inevitable that many escape (some are turned loose).
  • 81. Biotic Rearrangement: The Sad Case of Florida
    • Dozens of species of exotic plants have become widespread, and most are expanding their ranges.
    • Spread of melaleuca tree has changed swamps to forests.
    • Aquatic weeds infest more than half a million acres of waters.
    • Many exotic animal species well established and some spreading rapidly.
    • Exotic fish more numerous and pose even more serious problems, competing with native species.
    • Greatest present and potential threat is so-called walking catfish from Southeast Asia.
    Salt Cedars
  • 82. Focus: Desert Adaptations of the Amazing Camel
    • Dromedary (one-humped) camel has developed the most remarkable series of adjustments to desert environment.
    • Anatomical adaptations include
    • Light-colored and shiny summer coat reflects hot sunlight.
    • Deeply cleft upper lip allows moisture loss from nose to be recycled back into mouth.
    • Nostrils are horizontal slits that keep sand and dust out.
  • 83. Focus: Desert Adaptations of the Amazing Camel
    • Eyes set beneath shaggy brows for shade, and double eyelids to protect eyes from sand.
    • Broad and elastic feet for good traction and protection against the hot sand.
    • Physiological adaptations include
    • Highly fluctuating body temperatures that allow them to conserve moisture through minimal perspiration.
    • Little production of urine and little moisture voided in their feces.
    • Can stand long periods without water and can rapidly rehydrate when drinking.
    • They cannot, however, store moisture in their hump.
  • 84. People and the Environment: Rainforest Loss in Brazil
    • Brazil contains about one-third of the planet’s tropical rainforest.
    • Settlement over the last 50 years in the forest has led to large tracts of it being cleared for settlement and logging.
    • This clearing has been facilitated by the construction of the Cuiabá-Port Velho highway.
    • By the late 1980s deforestation had increased substantially, and by 2001 the amount removed was extraordinary.
    • In 2004, more than 26,000 square kilometers of rainforest were lost.
    • Much of the land is cleared for grazing land, which is then abandoned after a couple of years due to the poor fertility of tropical soils.
    • This is leading to habitat and species loss in the region.

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