in arid regions, water evaporates leaving salts behind. (ex. Fertile crescent, southwestern US)
water completely saturates soil starves plant roots of oxygen, rots roots
Hydrologic Cycle Components
evaporation, transpiration, runoff, condensation, precipitation, and infiltration.
all of the land that drains into a body of water.
underground layers of porous rock allow water to move slowly.
Cone of Depression
lowering of the water table around a pumping well.
Salt Water Intrusion
near the coast, overpumping of groundwater causes saltwater to move into the aquifer.
El Nino Southern Oscillation, trade winds weaken & warm surface water moves toward South America. Diminished fisheries off South America, drought in western Pacific, increased precipitation in southwestern North America, fewer Atlantic hurricanes.
"Normal" year, easterly trade winds and ocean currents pool warm water in the western Pacific, allowing upwelling of nutrient rich water off the West coast of South America.
because atmospheric N cannot be used directly by plants, it must first be converted into ammonia by bacteria.
decomposers covert organic waste into ammonia.
ammonia is converted to nitrate ions (NO3-).
inorganic N is converted into organic molecules such as DNA/amino acids & proteins.
bacteria convert ammonia back into N.
does not exist as a gas; released by weathering of phosphate rocks, it is a major limiting factor for plant growth. Phosphorus cycle is slow, and not atmospheric.
plants convert CO2 (atmospheric carbon) into complex carbohydrates (glucose C6H12O6).
oxygen consuming producers, consumers & decomposers break down complex organic compounds & convert C back into CO2.
the living components of an ecosystem.
the nonliving components of an ecosystem.
organisms that make their own food—photosynthetic life (plants).
10% of the usable energy is transferred to the next trophic level. Reason: usable energy lost as heat (2nd law of Thermodynamics), not all biomass is digested & absorbed, predators expend energy to catch prey.
development of communities in a lifeless area not recently inhabited by life (ex. lava flow, retreating glacier).
life progresses where soil remains (ex. clear-cut/burned forest, old farm, vacant lot).
symbiotic relationship where both organisms benefit.
symbiotic relationship where one organism benefits & the other is unaffected.
relationship in which one organism (the parasite) obtains nutrients at the expense of the host.
the number of individuals that can be sustained in an area.
reproductive strategy in which organisms reproduce early, bear many small, unprotected offspring (ex. insects, mice).
reproductive strategy in which organisms reproduce late, bear few, cared for offspring (ex. humans, elephants).
organisms that possess favorable adaptations pass them onto the next generation.
"human population cannot continue to increase. Consequences will be war, famine & pestilence (disease)."
(rule of 70) doubling time equals 70 divided by percent growth rate. (ex. a population growing at 5% annually doubles in 70 ÷ 5 = 14 years)
Replacement Level Fertility
the number of children a couple must have to replace themselves (averages 2.1 in more developed nations, 2.7 in less developed nations).
a little over 6 billion.
birth & death rates high, population grows slowly, infant mortality high.
death rate (infant mortality) lower, birth rates remain high, better health care, population grows fast.
decline in birth rate, population growth slows.
low birth & death rates.
Age Structure Diagrams
broad base → rapid growth; narrow base → negative growth; uniform shape → zero growth
Most Populous Nations
(1) China; (2) India; (3) U.S.; (4) Indonesia
Low Status of Women
Most important factor keeping population growth rates high.
Methods to Decrease Birth Rates
family planning, contraception, economic rewards & penalties.
source from specific location such as pipe or smokestack
Non-Point Source (Area/Dispersed Source)
source spread over an area such as agricultural/feedlot runoff, urban runoff, traffic.
Primary Sewage Treatment
first step of sewage treatment; eliminates most particulate material from raw sewage using grates, screens, and gravity (settling).
Secondary Sewage Treatment
second step of sewage treatment; bacteria breakdown organic waste, aeration accelerates the process.
Biological Oxygen Demand, amount of dissolved oxygen needed by aerobic decomposers to break down organic materials.
rapid algal growth (algal bloom) caused by an excess of nitrogen & phosphorus, blocks sunlight, causing the death/decomposition of aquatic plants, decreasing dissolved oxygen (DO), suffocating fish.
water with very low dissolved oxygen levels, the end result of eutrophication, for example.
Corporate Average Fuel Economy standards enacted into law in 1975, established fuel efficiency standards for passenger cars and light trucks. The fuel economy ratings for a manufacturer's entire line of passenger cars must currently average at least 27.5 mpg for the manufacturer to comply with the standard.
Primary Air Pollutants
produced by humans & nature (CO, CO2, SO2, NO, hydrocarbons, particulates).
Secondary Air Pollutants
formed by reaction of primary pollutants.
sources include burning fossil fuels and car exhaust. Effects include reduced visibility, respiratory irritation. Methods of reduction include filtering, electrostatic precipitators, alternative energy).
(NOx) Major source is auto exhaust. Primary and secondary effects include acidification of lakes, respiratory irritation, leads to smog and ozone. Reduced using catalytic converters.
Equation for acid formation
NO + O2 → NO2 + H2O → HNO3.
Secondary pollutant, NO2 + UV → NO + O; O + O2 → O3, with VOCs. Causes respiratory irritation and plant damage. Reduced by reducing NO emissions and VOCs.
(SOx) Primary source is coal burning. Primary and secondary effects include acid deposition, respiratory irritation, plant damage. Reduction methods include: scrubbers, burn low sulfur fuel.
Equation for acid formation
SO2 + O2 → SO3 + H2O → H2SO4
(CO2) Sources include the combustion of fossil fuels. Effects: greenhouse gas-contributes to global warming. Reduction accomplished by increased fuel efficiency (gas mileage), mass transit (reduction).
(CO) Sources include incomplete combustion of fossil fuels. Effects: binds to hemoglobin reducing bloods ability to carry O2. Reduction accomplished by catalytic converters, oxygenated fuel, mass transit (reduction).
formed by chemical reactions involving sunlight (NO, VOC, O2)
caused by sulfuric and nitric acids resulting in lowered pH of surface waters
Most significant: H2O, CO2, methane (CH4), CFCs. Trap outgoing infrared energy (heat) causing earth to warm.
a vital process, required for life to exist on Earth. If accelerated, bad, leads to global warming.
Effects of Global Warming
rising sea level (due to thermal expansion not melting ice), extreme weather, droughts (famine), and extinctions.
caused by CFCs, methyl chloroform, carbon tetrachloride, halon, methyl bromide all of which attack stratospheric ozone. Negative effects of ozone depletion include increased UV, skin cancer, cataracts, and decreased plant growth.
Municipal Solid Waste
is mostly paper and mostly put into landfills.
problems include leachate, which is solved using a liner with a collection system; methane gas, which may be collected and burned; and the volume of garbage, which may be compacted and/or reduced.
Advantages-volume of waste reduced by 90% and waste heat can be used. Disadvantages-toxic emissions (polyvinyl chloride, dioxin), scrubbers and electrostatic precipitators needed, ash disposal.
Best Solution for Waste Problem
reduce the amount of waste at the source.
abandoned industrial sites.
species whose role in an ecosystem is more important than others.
species that serve as early warnings that an ecosystem is being damaged.
In Natural Ecosystems
50-90% of pest species are kept under control by: predators, diseases, parasites.
the amount of a chemical that kills 50% of the animals in a test population
first layer of atmosphere 0-10 miles above the Earth's surface. Contains weather, greenhouse gases (bad ozone).
second layer of atmosphere 10-30 miles above the Earth's surface. Contains protective ozone layer (good ozone).
Inversion Layer (Temperature Inversion)
a warm layer of air above a cooler layer traps pollutants close to the Earth's surface.
substances that cause changes in DNA; may result in hereditary changes.
substances that cause fetus deformities (birth defects).
substances that cause cancer.
one of the most toxic human-made chemicals. Stable, long-lived, by-product of herbicide production enters environment as fallout from the incineration of municipal and medical waste and persists for many years.
PCBs (Polychlorinated Biphenyls)
Stable, long-lived, carcinogenic chlorinated hydrocarbons. Produced by the electronics industry.
Multiple Use Public Lands
National Forest & National Resource lands.
Moderately Restricted Use Public Lands
National Wildlife Refuges
Restricted Use Public Lands
National Parks & National Wilderness Preservation System
Divergent Plate Boundaries
tectonic plates spreading apart, new crust being formed (ex. mid-ocean ridges, rift valleys).