parasite box model example brucellosis (undulant fever) is a bacterial disease of ruminant mammals...
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Parasite Box Model Example
• Brucellosis (undulant fever) is a bacterial disease of ruminant mammals and sometimes of humans. In ruminants, brucellosis causes a decrease in milk production, and can cause cows to abort their calves. It has been in the news because of concern that brucellosis infected bison in Yellowstone National Park may be able to spread the disease to cattle. Construct a box model and then write equations that show how brucellosis affects a population of bison. Once an animal is infected with brucellosis, it will carry the disease for the rest of its life. There is vertical transmission of the disease from mothers to offspring. In your box models and equations you should account for: x - the # of uninfected susceptible bison, y - the # of infected bison, a - per capita host birth rate for uninfected offspring, b - natural, non-disease mortality rate, alpha α - disease induced mortality rate, beta β - transmission coefficient, and zeta ζ - birth rate of infected young.
Symbioses - Mutualism
Endosymbiotic Origin of Eukaryotes
Lynn Margulis
Endosymbiotic Origin of Eukaryotes
Endosymbiotic Origin of Eukaryotes
• The earliest eukaryotes acquired mitochondria by engulfing alpha proteobacteria.
• The early origin of mitochondria is supported by the fact that all eukaryotes studied so far either have mitochondria or had them in the past. Mitochondria have their own DNA and replicate themselves during cell division.
• Later in eukaryotic history, some lineages of heterotrophic eukaryotes acquired an additional endosymbiont—a photosynthetic cyanobacterium—that evolved into plastids.
• This hypothesis is supported by the observation that the DNA of plastids in red and green algae closely resembles the DNA of cyanobacteria.
• Plastids in these algae are surrounded by two membranes, presumably derived from the cell membranes of host and endosymbiont.
Stromatolites on coast of Western Australia
The Nature of Communities and Ecosystems
Sourdough bread – ingredients and final product
Redwood Forest
Scale of Ecosystem – Lake Superior
Scale of Ecosystem – Isle Royale
Scale of Ecosystem – Isle Royale – Forest and Pond
Scale of Ecosystem – Isle Royale Wetland
Scale of Ecosystem – Isle Royale Pitcher Plants
Ecotone – region where two communities/ecosystems grade into each other
Forest-Marsh Ecotone
Stability
A stable community or ecosystem is one that has the ability to replace
itself – exist in place for more than one generation
Douglas-Fir
Pea Aphids
Life cycle of the Pea Aphid
Components of Stability
2 major components:
1) resistance - the ability of a community or ecosystem to avoid disturbance - how most people think of stability
2) resilience - the speed with which a community or ecosystem returns to its former state following a disturbance that has displaced it from its initial condition
Ecosystems and Stability
Grassland – South Africa Rainforest – Puerto Rico
Additional Components of Stability
• Local stability describes the tendency of a community to return to its original state following a small disturbance
• Global stability describes the tendency of a community to return to its original state following a large disturbance
Adaptive Capacity of an Ecosystem
Adaptive Capacity of an Ecosystem
Adaptive Capacity of an Ecosystem- Chesapeake Bay
Adaptive Capacity in 3D
Current Adaptive Capacity
From Local vs. Global Stability
• dynamically fragile - a community which is stable only within a narrow range of environmental conditions
• dynamically robust - a community which is stable within a wide range of environmental conditions
Complexity and Stability
Current understanding - no clear relation between complexity and stability
1) complex, fragile communities of relatively constant environments (the tropical rainforests) are more susceptible to outside, unnatural disturbances than are simpler, more robust communities which experience regular climatic fluctuations (most temperate communities)
2) In stable environments you would expect to find K selected species (high competitive ability, high survivorship, low reproductive output) and such species will resist disturbance
3) In unstable environments you would expect to find r selected species (low competitive ability, low survivorship, but high reproductive output) that have little resistance but high resilience
Aerial viewOf 1989Yellowstone Fire
Why is the World Green?
Boreal Forest Outlined in Green
Spiny Water Flea
Spiny Water Flea Invasion
MaryPower
Eel River with steelhead Eel River without steelhead