Chapter 10: Cycles and Patterns in the Biosphere
McKnight’s Physical Geography: A Landscape Appreciation,
Tenth Edition, Hess
Cycles and Patterns in the Biosphere
• The Impact of Plants and Animals on the Landscape
• The Geographic Approach to the Study of Organisms
• Biogeochemical Cycles• Food Chains• Natural Distributions• Environmental Relationships
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The Impact of Plants and Animals on the Landscape
• Vegetation grew profusely at one time
• Human modification of vegetation
• Animal life less apparent• Both interact with
components of the landscape
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Figure 10-1b
The Geographic Approach to the Study of Organisms
• Simplest organisms still extraordinarily complex• Seek patterns of distribution of living organisms—
biogeography• Several biological classification schemes
– Most common, binomial, “two name”• 600,000 species of plants; twice that of animals• Biota—total complex of plant and animal life
– Flora: plant life– Fauna: animal life
• Ocean biota—plankton, nekton, and benthos
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Biogeochemical Cycles
• Organisms survive through complex of systemic flows of energy, water, and nutrients
• Cycles through which Earth’s chemical elements are absorbed by organisms and returned to Earth through decomposition—biogeochemical cycles
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Figure 10-2
Biogeochemical Cycles
• The flow of energy– Sun is source on which all
life depends– Photosynthesis and
respiration– Food chain– Energy must be converted
to a usable form and recycled
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Figure 10-3
Biogeochemical Cycles
• Photosynthesis– Biosphere receives solar energy– Chlorophyll– Chemical equation
• CO2 + H2O = Carbohydrates + O2
– Energy distributed by animals eating plants or each other
– Energy distributed in the plants through respiration– Plant respiration equation
• Carbohydrates + O2 = CO2 + H2O + Energy (heat)
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Biogeochemical Cycles
• Net primary production– Net photosynthesis—
difference in carbohydrates produced to those lost to respiration
– Net primary production is the net photosynthesis over a year (Figure 10-4)
– Measure of chemical energy in a plant
– Reflected in the dry weight, or biomass, of the material
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Figure 10-4
Biogeochemical Cycles
• The Hydrologic Cycle– Every living thing depends
on water supply– Water dissolves nutrients
and carries them to all parts of the organism
– Two ways water is found in biosphere
• In residence: chemically bound to plant and animal tissue
• In transit: part of transpiration-respiration
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Biogeochemical Cycles
• The Carbon Cycle– Biosphere contains complex
mixture of carbon compounds– Main components
• Transfer of carbon from CO2 to living matter and back to CO2
– Rapid process (years not centuries)
– Gradual incorporation of stored carbon in rock
– Fossil fuels increase CO2
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Figure 10-6
Biogeochemical Cycles
• The Oxygen Cycle– Building block in most
organic molecules– By-product of plant life– Occurs in many forms
and is released in many ways
– Sources include water, carbon dioxide, ozone, oxygen stored in rocks
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Figure 10-7
Biogeochemical Cycles
• The Nitrogen Cycle– Nitrogen only usable in gas
form by a few bacteria– Nitrogen usable by other
organisms as nitrates that are used in plants—nitrogen fixation
– Waste converts nitrates to waste nitrites
– Bacteria convert nitrites back to nitrates and nitrogen gas (denitrification)
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Figure 10-8
Biogeochemical Cycles
• Other mineral cycles—other minerals critical to the biosphere– Phosphorous– Sulfur– Calcium
• Gaseous pathways—interchange between biota and atmosphere-ocean environment
• Sedimentary pathways—element is weathered and reaches the groundwater; returned to the ocean and is consumed by ocean organisms
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Food Chains
• Food chain—direct passage from one organism to another of nutrients
• More complex—food “web”
• Primary energy transformation mechanism
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Figure 10-9
Food Chains
• Fundamental unit: producers (autotrophs), self feeders
• Producers eaten by consumers (heterotrophs)– Primary consumers:
herbivores– Secondary consumers:
carnivores• Food pyramid• Decomposers begin the food
pyramid again
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Figure 10-10
Food Chains
• Energy is inefficiently consumed between different food pyramid levels
• Pollutants in the food chain– Biological amplification– Chemical pesticides and
heavy metals (mercury, lead)– Irrigation-related issues
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Figure 10-11
Natural Distributions
• Four basic conditions• Evolutionary development
– Survival of the fittest– Where did the genus
(closely related organism group) evolve?
• Some localized• Several scattered localities of
the same genus
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Figure 10-12
Natural Distributions
• Migration and dispersal– Animals move from one
place to another– Plants move through seed
dispersal– Distribution pattern of
organisms results from natural migration or dispersal from the original development center
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Figure 10-14
Natural Distributions
• Reproductive success– Ability for organisms to
reproduce affects distribution
– Factors resulting in poor reproductive success
• Heavy predation• Climate change• Food supply failure• Changing environmental
conditions
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Figure 10-16
Natural Distributions
• Extinction and die-off– Range diminution
• Small areal changes• Mass extinction
– Plant succession—one vegetation type replaced by another (Figure 10-17)
• Occur after catastrophic events• Primary succession—pioneer
community• Secondary succession
– Extinction versus succession
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Figure 10-17
Environmental Relationships
• Relationships of plants and animals depends on environment
• Influences depend on the area of interest– Large area: seasonal characteristics, location– Small area: localized terrain, topsoil
• Interspecific versus intraspecific competition• Limiting factor: most important variable for the
survival of an organism
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Environmental Relationships
• The influence of climate– Light
• green plants need light to survive• Light changes shapes of plants
(Figure 10-19)• Photoperiodism: stimulates
seasonal plant behavior
– Moisture• Distribution of biota governed
more by moisture than any other factor
• Biota evolution dictated by adaptation to moisture conditions
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Figure 10-19
Figure 10-20
Environmental Relationships
• The influence of climate– Temperature
• Different species can survive in different temperatures
• Plants have limited cold temperature tolerance
– Wind• Wind effects generally limited• Persistent winds can have limiting
effects through increased drying• Strong winds can be destructive
to biota
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Figure 10-21
Environmental Relationships
• Topographic influences– Plants and animals in a plains
region vastly different from a mountainous region
– Slope and drainage• Wildfires
– Result in complete or partial devastation of plant live and death or driving away of animals
– Can be helpful for regrowth and maintaining of plant type
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Figure 10-22
Environmental Relationships
• Example of selva (rainforest)– Occurs when climate is warm and
has abundant precipitation– Abundance of precipitation and
warmth leads to abundance of natural vegetation (flora), jungle
– Numerous plants allow for fauna– Leaves, trees, branches
decomposed by abundant fauna on floor, put into soil
– Water runoff
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Figure 10-24
Summary
• Plants and animals impact and interact with the landscape in numerous ways
• Need a classification scheme for biota to understand geographically
• Flora and fauna refer to plants and animals, respectively• Energy originates from the Sun and flows to organisms
through photosynthesis• The hydrologic cycle describes the transition of water
through the biosphere• The interaction of carbon with the biosphere is the carbon
cycle
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Summary
• Oxygen and nitrogen cycle through the biosphere through the oxygen and nitrogen cycles, respectively
• Other minerals cycle through the biosphere as well, but they are not as commonly observed
• Food chains describe the passage of energy from one organism to another
• There are four primary components to the natural distributions of biota
• Numerous environmental relationships affect which biota exist in which regions
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