Range and dispersal
General Ecology, factors, biomes
Interactions lead to organism and
population range limits and dispersal
limits. Both biotic and abiotic factors can
‘limit’ or define these.
Case: mussels in the intertidal
Case: Mazzaella parksii: a red intertidal alga.
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Community structure
Figure 3.23
Species tolerance
• Law of tolerance: the existence, abundance and
distribution of a species in an ecosystem are (largely)
determined by whether the levels of one or more
factors (abiotic) falls within the range of tolerance
• Tolerance to abiotic and biotic factors in part
determines the range/distribution
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Tolerance Cont.
• Acclimation: animal or plant is able to
adjust to changes.
– Some examples?
• Threshold effect:builds up with little
response until sudden inability to cope
– Some examples?
Tolerance Cont.
• Physiological responses
• Morphological responses
• Behavioral responses
• Community boundaries?
• Short term and long term
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Abiotic factors are important in
determining ecosystem structure
• Living things have tolerance limits to
abiotic factors such as…?
Range explanations
Species Interactions (Biotic):
Interspecific and Intraspecific
• Competition
• Predation
• Symbiosis
Behavioral responses
• A species never dispersed beyond its present
boundaries
• Pioneers failed to survive
• Range has been reduced over evolutionary time
• Pioneers became isolated/separated:
phylogeography
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Tolerance limits
Figure 3.2
Adaptation by the process
of Natural Selection
•Survival and differential reproductive
success over a period of time
•Traits that increase ‘fitness’ are ‘selected
for’, and are passed on through generations
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Figure 50.2 Patterns of distribution in the biosphere
Number of individuals
In tundra habitats above timberline, the alpine skypilot is pollinated primarily by bumblebees.
28
24
20
16
12
8
4
0
Number of individuals
10 12 14 16 18 20 22
Tundra flower:
Flower size (mm)
big and sweet-smelling
In forested habitats below timberline, the alpine skypilot is pollinated primarily by flies.
10
8
6
4
2
0
Below-timberline flower:
small and skunky-smelling
10 12 14 16 18 20 22
Flower size (mm)
Biomes
Biomes
•
•
•
•
• Animals and plants have narrow
ranges of tolerance to abiotic factors
What defines a biome?
Where are the ‘lines’ drawn?
What are the major controlling factors?
What about aquatic ‘biomes’
Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in North
America
• This in part determines the biotic
components of biomes. These are
broad geographic regions determined
by temperature and rainfall, and
described by their plant communities
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World biome map
Figure 5.3
5-1
3
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Figure 50.4 Solar radiation and latitude
Biome climate graphs
Figure 5.4
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Figure 50.5 The cause of the seasons
Figure 50.6a Global air circulation, precipitation, and winds
Figure 50.6b Global air circulation, precipitation, and winds
Figure 50.7 Rain shadows
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Figure 50.8 Lake stratification and seasonal turnover
Global winds
Figure 50.8 Lake stratification and seasonal turnover
Aquatic Biomes
•
•
•
•
•
•
•
Temperature
Currents
Nutrients
Salinity
Oxygen
Depth
Sunlight
•Oligotrophic
•Eutrophic
•Turnover rate
• Physical as well as chemical boundaries
Figure 50.9 The distribution of major aquatic biomes
Figure 50.13 Zonation in the marine environment
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Sea surface temperature
Currents
Biomes
•
•
•
•
What defines a biome?
Where are the ‘lines’ drawn?
What are the major controlling factors?
What about aquatic ‘biomes’
Some Key Points
• Animals interact with biotic and abiotic factors in ways
which shape their survival and distributions
• Biomes are delineated by abiotic factors, but biotic factors
play a role too.
• Biomes are described by plant communities which are
‘controlled’ by temperature and precipitation
• Oceans are different: currents and salinity/oxygen
distribution have a major impact - productivity
• Organisms have tolerance ranges to abiotic factors - both
long term and short term effects.
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