ECOLOGY
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Transcript of ECOLOGY
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ECOLOGY
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ECOLOGY
• Ecology – The study of the distribution and abundance of life, and the interactions between organisms and their environment.
• Population ecology – the study of changes in the size and composition of populations and factors that cause those changes.
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Isle Royale
• NW Lake Superior• ~50 miles long and ~8miles wide• Home to a population of wolves and moose (moose 90% of the wolves diet). • Longest study of any predator-prey system• Designated an International Biosphere Reserve
• 99% is legally designated wilderness
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•1900 – Moose swim 15 miles from Canada and arrive on Isle Royale. •In absence of wolves the moose were happy (see picture below).
•.1929 & 1930 – Adolph Murie makes the 1st scientific observations of the Isle Royale moose, and climate.
•1931 – Isle Royale became a national park as a “prime example of North Woods Wilderness.”
•Early 1930s – Moose food supply dwindles as well as moose population shortly there-after.
•1936 – A fire burned more than a quarter of the island
•1937 – Moose population crashed
•1940's – Fire stimulates growth of new browse and brood.
Isle Royale History
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•1948-1949 – Ice bridge forms between Canada and the island.
•Late 1940s & Early 1950s – Wolves were extirpated from nearly all 48 states and migrate to Canada
•Mid 1950s – A pack of Eastern timber wolves crossed over to Isle Royale.
•The lives of the Isle Royale moose were never the same……
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• 1958 – Durward Allen began studying the wolves and moose of Isle Royale
• 2008 – Wolves, moose, and researchers have been watching each other for 50 years.
• The world's longest running wildlife research project!
Ecology research
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Isolation fosters conditions favorable for studying nature!
1. Relatively few species have colonized Isle Royale.
2. Essentially they represent a single-prey-single-predator system.
• Wolves are the only predators of moose.• Moose are nearly the only prey (~10% beaver/hare)
3. Small number of species = simpler ecosystem.
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Wolf food webs
Isle Royale Yellowstone
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Simplified wolf food chain
Isle Royale is not too small, not too large, not too far, and not too close!
If Isle Royale were...• Smaller
too small to support a wolf population.• Larger
too large to effectively study the moose population.• Further from the mainland
wolves and moose may never have made it to island.
• Closer to the mainland mainland animals would have migrated over.
Studying species interactions becomes increasingly difficult with increasing species diversity.
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The EcoBeaker Version of Isle Royale
• Model (5 species)• 3 plants• Moose • Wolves
• Environment characteristics• Temperature • Seasonal changes• Plant growth
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Exponential Growth Model:
Growth rate (r) increases with increases in population size...
Assumes population increase at maximum per capita rate of growth (r
max).
Instantaneous change (dN/dt) represents changes in population size with respect to time.
Limitation: Applicable only to a very small population. Population size levels off at carrying capacity!
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Logistic Growth Model:
Carrying capacity (K) - the maximum number of individuals of that species that the local environment can support at a time.
Growth rate (r) decreases as the population density increases.
When N = K, the population will no longer grow!
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Key Stone PredatorEcological Community – is a group of species that live together and interact with each other.
Community Structure – the composition and relative abundance of the different types of organisms present.
Intertidal Community – comprised of organisms living in the area covered by water at high tide and exposed to the air at low tide.
Keystone Predator – a predator that has an exceptionally great impact on the other species in its ecosystem relative to its abundance
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Experiment
• Simulated experiment based on 1960’s experiments conducted along the rocky shore of Washington.
• You will observe which intertidal species is dominant over one another to construct a food web diagram.
• Then you will remove a species and see how it influences the community.
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Food Chains, Food Webs and Trophic Levels
Lowest Tropic Level –Producers - (algae and green plants) use energy from the sun to produce their own food
Herbivores - consume producers.
Higher Tropic Level – Predators eat herbivores
Omnivores - take up multiple levels!
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Next week……Good luck on the final!
THENTHEN…
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