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Visualizing Physical Geography by Alan Strahler and Zeeya Merali Chapter 16 Biogeographic Processes Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Energy and Matter Flow in Ecosystems Biogeography: the study of the distribution patterns of organisms over space and time and of the processes that produced these patterns Ecosystem? Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Energy and Matter Flow in Ecosystems The Food Web Food web (food chain): organization of an ecosystem into levels through which energy flows as the organisms at each level consume energy from the bodies of organisms in the level below • Primary producers: ? • Consumers: ? • • • • Decomposers: ? Energy is lost at each level in food web by respiration Only 10 to 50% of the energy stored at one level passes up to the next level Normally, about 4 levels of consumers Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Food Web Energy and Matter Flow in Ecosystems Photosynthesis and Respiration Photosynthesis: production of carbohydrate from water and carbon dioxide, using light energy H20 + CO2 +light energy CHOH + O2 Rates of photosynthesis depend on light intensity, duration of daylight, and temperature Energy and Matter Flow in Ecosystems Photosynthesis and Respiration Respiration: carbohydrate is broken down and combines with oxygen to yield carbon dioxide and water, releasing energy CHOH + O2 CO2 + H2O + chemical energy Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Energy and Matter Flow in Ecosystems Net Primary Production Net primary production: annual yield of useful energy produced by the ecosystem, in grams/square meter/year Biomass: dry weight of living organic matter in an ecosystem within a designated surface area (grams/square meter or metric tons/hectare Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Carbon cycle: biogeochemical cycle in which carbon moves through the biosphere The Nitrogen Cycle Ecological Biogeography Ecological biogeography examines the distribution patterns of plants and animals from the viewpoint of their physiological needs Habitat: subdivision of the environment according to the needs and preferences of organisms or groups of organisms Ecological niche: ? Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Water Need Xerophyte: plant adapted to dry conditions • Phreatophytes: plants that obtain water from ground water Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Water Need Some climates have yearly wet and dry seasons: wet-dry tropical climate, moist continental climate, Mediterranean climate Tropophyte: plant adapted to changing conditions/dry season alternating with wet season • Deciduous: plants that drop their leaves seasonally • Evergreens: plants that keep most of their leaves more than 1 year • Mediterranean climate plants often xerophytic, evergreen, with hard, leathery leaves (sclerophylls) Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Water Need Xeric animals: • Many invertebrates dormant during dry periods • Many birds only nest when rains occur • Many desert animals active only at night, stay in burrows in the day • Many desert mammals do not sweat through skin glands Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Temperature Temperature affects: • Rate of physiological processes • Water availability Adaptations to cold: ? Adaptations to heat: ? Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Other Climatic Factors Light affects: • Plant distribution • Plant growth rate • Timing of budding, flowering, fruiting, leaf shedding • Animal behavior • Daily cycles • Preparation for winter • Mating and reproduction Wind affects vegetation structure Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Edaphic Factors Edaphic factors are connected to soil Soils affect plant growth; plants affect soil characteristics • Sandy soils hold less water • High organic matter in soils supports more plant species • Prairie grassland can build fertile soil Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Disturbance Disturbance includes: fire, flood volcanic eruption, storm waves, high winds Fire benefits: ? Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Interactions Among Species • • • • • • Competition: ? Predation: ? Parasitism:? Herbivory: ? Allelopathy: ? Symbiosis:? • Commensalism: one species benefits, the other is unaffected • Mutualism: one or both species cannot survive alone Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Biogeography Interactions Among Species Importance of predation: Rise and fall of the Kaibab deer herd Predators removed deer population expanded deer overgrazed the vegetation and starved deer population crashed Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Succession Ecological Succession: sequence of distinctive plant and animal communities occurring within a given area of newly formed land or land cleared of plant cover by burning, clear cutting, or other agents Primary succession: succession on a new deposit of rock or mineral fragments Secondary succession: succession on a previously vegetated area that has been disturbed Primary succession on coastal dunes Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Succession Secondary succession on old fields, southeastern U.S. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Ecological Succession Disturbances may interrupt succession, alter ecosystems and change successional pathways • Wind • Fire • Floods • Introduction of new species Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Evolution Evolution: the creation of diversity of life-forms through the process of natural selection Natural selection: selection of organisms by the environment in a process similar to selection of plants or animals for breeding by agriculturalists Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Species: ? Evolution Natural selection: life posses variation Individuals with qualities best suited to the environment are more likely to propagate: “survival of the fittest” Sources of variation: 1. Mutation: changes in genetic material 2. Recombination: offspring receives 2 slightly different copies (alleles) of each gene from parents Genus: collection of closely related species that share a similar genetic evolutionary history Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Speciation: the process by which species are differentiated and maintained Speciation arises from several processes acting over time • Mutation • Natural selection • Genetic drift: chance mutations that don’t have any particular benefit, change the genetic composition of a population • Gene flow: opposite to genetic drift--populations exchange genes as individuals move among populations; keeps gene pool uniform Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Speciation in Galapagos finches Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Extinction All species become extinct over geologic time Conditions change, and species unable to adapt become extinct Human activities may cause extinctions Catastrophic natural events may cause extinctions Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Distribution Patterns Endemic species: species found in one location or region, and nowhere else Cosmopolitan species: distributed very widely Disjunction: one or more closely related species found in widely separated regions Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Historical Biogeography Biogeographic Regions Closely related species often found near each other Some species have disjunct distributions Ratite birds and tinamous are related; isolated when Gondwana split up Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Biodiversity Biodiversity: the variety of biological life on Earth or within a region Humans have created extinctions by ? Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Biodiversity Human Impact on the Biosphere Biodiversity Hotspots Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.