Sunday, November 6, 2011
Monday, September 12, 2011
Investigate and analyze the critical abiotic and biotic factors that define an ecosystem. To accomplish your mission successfully, you will need to:
Understand the dynamics of ecology.
Explain how limiting factors influence carrying capacity.
Compare and contrast the major ecosystems of the world.
Describe the processes of photosynthesis and chemosynthesis.
Trace the flow of energy through an ecosystem.
Discover how abiotic factors are distributed, stored, and
recycled on the planet.
Explain how abiotic and biotic factors influence an ecosystem.
What Is Ecology?
Picture this: the sun rises over the African savannah.
A giraffe stretches to nibble the acacia tree’s tiny leaves, carefully avoiding the stinging ants that live within the tree’s long thorns. Wildebeests and gazelle graze on grass that flourishes in volcanic soils set down long ago by the pulling apart of Earth’s tectonic plates.
A cheetah sits high on a rocky outcrop—searching for a meal that she will share with her cubs. Vultures watch from above, ready to pounce on the remains of the cheetah’s catch.
A family of warthogs scurries around a termite mound, disturbing an ostrich as she flutters her feathers in the dust to shake off unwanted parasites.
Now put yourself in that scene. Are you the predator or are you prey? How will you survive? What will you need? Where are the threats? What are the dangers?
How will you get what you need without being eaten?
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Thursday, September 1, 2011
Hurricane Katrina : A Problem-Based Learning Module
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Katrina was one of the most powerful hurricanes ever, and will go down as the costliest natural disaster in recorded memory. At one point, wind speeds topped 170 mph, and surface pressures tanked to below 905 mb—extraordinary for an Atlantic hurricane. She resembled to epitome of all Atlantic hurricanes, and revealed the staggering amount of suffering a storm of her magnitude (Category 3 at landfall) can cause to those unprepared.
Katrina had her origins in the Bahamas as a rather disorganized area of cloudiness and thunderstorms. During her early stages of development, the would-be Katrina looked like a sloppy concoction of disorganized cloudiness, and it seemed improbable that this area of low pressure could develop into anything consequential. During the afternoon hours of 23 August, a Hurricane Reconnaissance Aircraft, along with buoy data and ship reports indicated that the area of disturbed weather in the southeastern Bahamas had become organized enough to be classified as a Tropical Depression (TD12)1. A short 24 hours later, the shoddy mass of convection had organized into a concentrated area of showers and thunderstorms just east of Nassau, and was named Tropical Storm Katrina2.
Katrina continued on a lazy westward track towards eastern Florida through the next 24 hours, and became a hurricane during the afternoon of 25 August, just 30 miles south-southeast of Boca-Raton, FL3. At this point, Katrina looked like a healthy, developing hurricane with cloud top temperatures as low as –80C. It was expected that Katrina would weaken shortly after making landfall in southern Florida, but she veered slightly off course and passed over the very moist Everglades south of lake Okeechobee, and was able to maintain hurricane intensity into the extreme eastern Gulf of Mexico.
On 26 August, Katrina entered the Gulf of Mexico, where shear was low and Sea Surface Temperatures (SSTs) were high, ranging from 30-32C—a perfect environment for intensification. During the overnight hours of 27 August, Katrina’s central pressure dropped from 950 mb, to nearly 930 mb—all in less than 12 hours. Early on 28 August, the National Hurricane Center revised the intensity of Katrina upwards to a Category 5 with surface winds near 160 mph. Less than three hours later, Hurricane Hunters measured a 166 kt flight level winds, and a 907 mb central pressure, which corresponded to surface wind speeds close to 175 mph—absolutely astonishing for an Atlantic Hurricane4.
In a report issued by the Hurricane Center on December 20, 2005, Katrina made landfall as a strong Category 3 storm, instead of the Category 4 as originally thought.5 Still, the incredibly high storm surge coupled with the strong winds proved too much for the New Orleans area to bear, and the consequences were unfathomable. As the Hurricane Center’s Tropical Cyclone Report so eloquently states:
“The scope of human suffering inflicted by Hurricane Katrina in the United States has been greater than that of any hurricane to strike this country in several generations.”New Orleans, LA