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1. Both primary and secondary succession are processes by which ecosystems reestablish their populations after a disturbance. The difference is that primary succession must start from scratch, re-forming soil from the rocks that remain. It takes much longer than secondary succession (which has intact soil).
2. A renewable resource can be replaced at the same rate by which it is consumed. Give an example of this type of resource: solar, wind, hydroelectric, or geothermal energy.
3. Secondary pollutants are created when primary pollutants undergo chemical reactions in the atmosphere. Primary pollutants are released directly into the atmosphere from burning fossil fuels.
4. When excess fertilizer enters a body of water, the phosphorus causes an algal bloom (phosphorus is normally a limiting factor and keeps algal growth in check). The overgrowth of algae soon begins to die, and decomposers begin to consume the dead algae. The decomposers are undergoing massive amounts of cellular respiration and using up tons of oxygen in the process, leading to hypoxic (low oxygen) conditions in the water. This causes a die-off of aquatic animals and plants.
5. a. Chernobyl nuclear contamination (SS), b. California wildfires (SS), c. Mount St. Helens volcanic eruption (either PS or SS, depending on severity of damage. If soil remains intact, it is SS.), d. Deforestation of Amazon rainforest (SS), e. Retreating glaciers in Alaska (PS).
6. Lichen is a pioneer species that is able to live on the newly exposed rocks and help break them down into soil (the first step of primary succession).
7. Burning fossil fuels releases carbon dioxide into the atmosphere. The CO2 in the atmosphere (along with other greenhouse gases) absorbs the infrared radiation released from the heated earth, warming the air.
8. a. As natural gas is removed and used as a fuel source, it is not replaced (at least not at a measurable rate). Therefore, it is not a renewable fuel source.