Environmental Engineering Reference
In-Depth Information
Although this lab is often referred to as lethal dose (LD), most labs for AP Environmental Science are actually
lethal concentration (LC) labs, in which test organisms are placed in a known concentration of the test medium.
LD is the lethal dose that the organisms receive. The 50 refers to the number of the test organisms that die, in
this case 50 percent. The number can be changed for different criteria. Often, copper sulfate is used with brine
shrimp. The brine shrimp are placed in a range of copper sulfate solutions. After 24 hours, a count of live and
dead brine shrimp is made and the number of dead shrimp is plotted on a graph. From the graph, you can de-
termine the threshold and the lethal concentration that causes 50 percent of the test organisms to die.
Oil Spill Cleanup
This activity involves cleaning up a simulated oil spill in water. Vegetable oil is poured into a pie tray contain-
ing water. A straw blows the oil around to simulate waves and wind in the oceans. Then students try a variety
of methods to remove the oil and leave the water behind. String and small straws can be used as booms to sur-
round the water. Cotton balls and pads, cloth, newspaper, and a variety of other material can be used to absorb
the oil. At the end, the water is dumped out and students can feel how much oil remains on the pie tray.
Predator-Prey Simulation
This lab demonstrates the relationship between population sizes of predators and prey, usually mice and
coyotes. When predator numbers decline, prey numbers increase, and when predator numbers rise, prey num-
bers decrease. Similarly, more prey leads to more predators, and fewer prey leads to fewer predators. This lab
is conducted with pieces of paper representing mice and coyotes. Data is recorded after each round, represent-
ing generations, and a cyclical pattern of population numbers should emerge.
Productivity
In this lab, grass captures energy from the sun through the process of photosynthesis, resulting in a measured
increase in the biomass of grass (the net primary productivity). The gross primary productivity is the amount of
biomass produced by photosynthesis per unit of area over time. The net primary productivity is the production
of glucose during photosynthesis minus the energy from glucose used to complete cellular respiration in the
plant during photosynthesis.
Population Growth in Lemna minor
Lemna minor, also known as duckweed, is commonly used as an aquatic test plant for new pesticides and re-
moves nitrates and phosphates in wastewater. It also can be harvested, dried, and used as feed for animals, es-
pecially chickens. In AP Environmental Science, this lab involves measuring the growth of duckweed in wa-
ters containing varying concentrations of nitrates, phosphates, pesticides, or salts.
Porosity
In this lab, different soil samples are collected in tubes capped on the bottom end. Samples usually include
gravel, sand, and fine sand. Water is then poured into the sample and the length of time it takes for water to
reach the bottom is recorded. The activity illustrates the fact that porosity and permeability increase with larger
particle size. Soil that has tighter pore spaces and smaller particles has a greater chance of runoff and flooding
because water cannot permeate easily.
To calculate percent porosity, use the following formula:
Percent Porosity = Volume of Voids ÷ Total Holding Volume × 100
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