ECOLOGY. ECOLOGY. Ecology – The study of the distribution and abundance of life, and the interactions between organisms and their environment. Population ecolog y – the study of changes in the size and composition of populations and factors that cause those changes. NW Lake Superior
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.
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 Isle Royale
Isle Royale History • 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.
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……
Ecology research • 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!
Isolation fosters conditions favorable for studying nature! • Relatively few species have colonized Isle Royale. • 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) • Small number of species = simpler ecosystem.
Wolf food webs Isle Royale Yellowstone
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.
The EcoBeaker Version of Isle Royale • Model (5 species) • 3 plants • Moose • Wolves • Environment characteristics • Temperature • Seasonal changes • Plant growth
Exponential Growth Model: Growth rate (r) increases with increases in population size... Assumes population increase at maximum per capita rate of growth (rmax). 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!
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!
Key Stone Predator Ecological 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. Keystone Predator – a predator that has an exceptionally great impact on the other species in its ecosystem relative to its abundance Intertidal Community – comprised of organisms living in the area covered by water at high tide and exposed to the air at low tide.
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.
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!
Next week…… • Good luck on the final! • THEN…