Transcript Why things live where they do

Who Lives Where, and Why?
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Tolerance limits and evolution
Evolution and Ecosystems
Ecosystems/Community Properties
Communities in Transition - Succession
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Fig. 4.4
i.e. Temperature or
Precipitation
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Cold,
oxygenrich
water
Can tolerate warm, low
oxygen water
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Adaptation
• Two types of adaptation
i.e., acclimation – dogs growing
– By individuals
Winter coat
• Adjustment to conditions
– By population
• Through genetic mutations creating new traits
• When a population adapts and a new species is
created, this is evolution
– Evolution operates by Natural Selection
Survival of the fittest OR more successful
at passing on their genes
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Similar to Fig. 4.9
Specialized according
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to food source
Evolution
• New species are created through Natural Selection, when adaptive
traits make it possible for a segment of the population to survive
in a different environment and/or use a new resource.
– New trait created by random genetic mutations
– Trait improves survival and so gets passed on to future
generations
– Over time, segment of the population with new trait becomes
separated from the rest of the population and the two no longer
interbreed.
– Once interbreeding ends, the two are now separate species
• Number of species limited by how far the resources can be
partitioned
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Partitioning
of winter
feeding grounds
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Evolution
• Number of species limited by how far the
resources can be partitioned
• Each species carves out its ecological niche
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Competition for resources causes
evolution
Fig. 4.7
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Fig. 4.8
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Evolution to Ecosystems
• Evolution creates new species
• Species live in and compose biota in ecosystems
– Species: Small scale, adapted to a
microenviroment – small spatial scale
– Ecosystems: Large scale, adapted to a
macroenvironment – large spatial scale
• Ecosystems include biota (communities of
organisms) and their physical environment (i.e.
atmosphere/crust or ocean)
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BIOTA: Important concepts for
Environmental Science
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Community productivity
Community complexity
Community resilience
Community changes with time
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Community Properties
• Productivity
– Primary: converting solar energy to chemical
energy
• Can be very productive, but not necessarily efficient
• Abundance and diversity of species
– often inversely related
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Fig. 4.21
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Energy from Sun!
Extremely high
Productivity
Systems:
Tropical rain forests
Coral reefs
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Community Properties
• Productivity
– Primary: converting solar energy to chemical
energy
• Can be very productive, but not necessarily efficient
• Abundance and diversity
– often inversely related
• Complexity
Will depend on community
• Resilience and stability
structure (keystone species?)
and distribution of nutrients
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Keystone Species
• Species that is key to Community structure
– Analogy: Pick-up sticks are Community of
species, the stick that you pull out and they all
fall down is a keystone species
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Giant Kelp is keystone sp. on Pacific
Coast of California
• Provides food, shelter and
structure for whole
community, affecting
resiliency of ecosystem to
change
• Ecosystem severely
impacted when sea otters
were hunted, as they ate
fewer urchins, which could
then eat more kelp
Fig. 4.20 – sea otters
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Communities in Transition
• Primary and secondary succession
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Secondary
Primary
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Fig. 4.26
After Ice Age,
for example
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Pioneer Community on Hawaiian Lava
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Kettle Lakes
in glaciated regions like Minnesota
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Eastern trees
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Succession and Climax Communities
• Do communities always return to the same group of
species?
– NO
– Example:
– Addition of P to lake with submerged plants initially
makes plants grow more
– If P gets high enough, floating communities (algae and
other plankton) shade bottom and submerged plants die
– If P goes back down, submerged plants may not come
back because floating communities will remain and
sediments have built up on the bottom
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Worries for Succession in MN forests
• Global warming
– Species with different tolerance limits step in
– Diseases/pests more successful with warmer
climate
• Invasive species
– Non-native species out compete native species
and change community
– Non-native Pests challenge native species
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The End.
Back
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