APES all units

What is the enhanced greenhouse effect and how does it differ from the natural greenhouse effect?

The natural greenhouse effect: CO₂, CH₄, and H₂O naturally trap heat — essential for maintaining Earth's temperature for life. The enhanced effect: human emissions amplify this trapping, causing net warming of the climate system.

Which greenhouse gas has the highest 100-year global warming potential (GWP)?

SF₆ (sulfur hexafluoride) has a GWP of ~23,500, but it is rare. Methane (CH₄) has a GWP ~28–36 times CO₂; nitrous oxide (N₂O) ~273 times. CO₂ is most significant overall because of its sheer volume and long atmospheric lifetime

What is stratospheric ozone depletion and what chemicals cause it?

CFCs (chlorofluorocarbons) and HCFCs release chlorine atoms in the stratosphere. Each Cl atom can destroy thousands of O₃ molecules, thinning the ozone layer and allowing harmful UV-B radiation to reach Earth's surface

What was the Montreal Protocol and why was it significant?

A 1987 international treaty that phased out production and use of ozone-depleting substances (CFCs, HCFCs). Widely considered the most successful environmental treaty in history — stratospheric ozone is now slowly recovering.

What are climate feedback loops? Give a positive and a negative example.

Positive feedback (amplifies warming): melting Arctic sea ice exposes dark ocean, absorbing more heat → more warming. Negative feedback (dampens warming): more warming → more evaporation → more clouds → more sunlight reflected back to space.

What is the difference between climate change mitigation and adaptation?

Mitigation: actions to reduce greenhouse gas emissions and slow climate change (renewables, energy efficiency, reforestation, carbon capture). Adaptation: adjustments to cope with current and expected climate impacts (sea walls, drought-resistant crops, early warning systems).

What is the difference between point source and nonpoint source pollution?

Point source: pollution from a single, identifiable source (e.g., a factory discharge pipe or sewage outfall) — easier to regulate. Nonpoint source: from diffuse, widespread areas (e.g., agricultural runoff, urban stormwater) — harder to control.

What is biomagnification? Give an example.

The increasing concentration of a persistent toxin at higher trophic levels. Example: DDT accumulates from plankton → small fish → large fish → osprey, reaching concentrations that cause eggshell thinning and reproductive failure in top predators.

What is bioaccumulation and how does it differ from biomagnification?

Bioaccumulation: the buildup of a toxic substance within a single organism over time (input > excretion). Biomagnification: the increasing concentration of a toxin as it moves up through multiple trophic levels in a food chain.

What are endocrine disruptors and what are their environmental effects?

Chemicals (e.g., PCBs, atrazine, BPA, phthalates) that mimic or block hormones. Environmental effects include reproductive failure, developmental abnormalities, and feminization of male fish near treated wastewater outfalls.

What is the Clean Water Act and what does it regulate?

A 1972 US law that regulates the discharge of pollutants into US waters and establishes water quality standards. It requires NPDES permits for point-source discharges and funds construction of municipal sewage treatment plants.

What are the six EPA criteria air pollutants?

Carbon monoxide (CO), Lead (Pb), Ground-level ozone (O₃), Particulate matter (PM₂.₅ & PM₁₀), Nitrogen dioxide (NO₂), and Sulfur dioxide (SO₂). These are regulated under the Clean Air Act because of well-documented health effects.

What causes acid deposition and what are its effects?

SO₂ and NOₓ from burning fossil fuels react with atmospheric water vapor to form sulfuric and nitric acids. Effects include acidification of lakes and streams, forest damage, soil nutrient leaching, and corrosion of buildings and monuments.

What is photochemical smog and how does it form?

NOₓ and VOCs (from vehicles and industry) react in the presence of sunlight to produce ground-level ozone and peroxyacetyl nitrates (PANs). Worst on hot, sunny, low-wind days — common in cities like Los Angeles and Houston.

What are the health effects of particulate matter (PM₂.₅)?

Fine particles (diameter < 2.5 micrometers) penetrate deep into lung tissue and enter the bloodstream. Health effects include respiratory disease, cardiovascular disease, asthma exacerbation, lung cancer, and premature death.

What is a thermal inversion and why does it worsen air pollution?

Normally, warm surface air rises and carries pollutants upward. In a thermal inversion, a warm air layer sits above cooler surface air, acting as a lid that traps pollutants near the ground — dramatically worsening local air quality.

What are the major differences between renewable and nonrenewable energy?

Renewable sources replenish naturally on human timescales (solar, wind, hydro, geothermal, biomass). Nonrenewable sources form over millions of years and are depleted by use (coal, oil, natural gas, uranium).

What is fracking (hydraulic fracturing) and what are its environmental concerns?

Injecting high-pressure fluid into rock to fracture it and release trapped natural gas or oil. Environmental concerns include groundwater contamination, methane leaks (a potent GHG), induced seismic activity, and large water consumption.

What is EROI (Energy Return on Investment)?

The ratio of energy obtained from a fuel to the energy required to extract it. High EROI (e.g., conventional oil ~25:1) = efficient. Low EROI (e.g., tar sands ~3:1) = energy-intensive and more environmentally costly to produce.

How does a nuclear power plant generate electricity?

Nuclear fission splits uranium-235 atoms, releasing enormous heat. The heat boils water into steam, which drives turbines connected to generators. Nuclear produces no direct CO₂ but generates long-lived radioactive waste.

What is the difference between active and passive solar energy?

Passive solar: building design uses sunlight directly for heating/cooling (south-facing windows, thermal mass). Active solar: mechanical systems capture and convert solar energy — photovoltaic panels or solar thermal collectors.

What is net metering in relation to solar energy?

A billing policy where solar panel owners can send surplus electricity back to the grid and receive credits on their utility bill. Net metering lowers the cost of going solar and incentivizes residential renewable energy adoption.

What are the main causes of soil erosion and how can it be prevented?

Causes: wind, water, overgrazing, deforestation, and tilling. Prevention: contour plowing, cover crops, windbreaks, no-till farming, terracing on slopes, and riparian buffers along waterways.

What is the tragedy of the commons?

When individuals acting in self-interest overuse and deplete shared (common) resources, leading to collapse. Examples: overfishing of common fishing grounds, overgrazing of public rangeland, groundwater depletion.

What is clear-cutting and what are its environmental impacts?

Removing all trees in an area at once. Environmental impacts: severe soil erosion, increased water runoff and flooding, loss of habitat and biodiversity, disruption of nutrient cycles, and long-term soil degradation.

What is eutrophication and what causes it?

Excess nutrients (especially N and P from fertilizer runoff) enter water bodies, triggering algal blooms. When algae die, decomposition depletes dissolved oxygen, creating hypoxic 'dead zones' where aquatic life cannot survive.

ground water

Groundwater is water found underground in porous rock or sediment.

aquifer

An aquifer is an underground layer of permeable rock or sediment that stores and transmits groundwater. The Ogallala Aquifer beneath the Great Plains is a major US example.

What is sustainable yield in the context of fisheries?

The maximum quantity of a renewable resource (e.g., fish) that can be harvested without depleting the population over time — meaning the harvest rate equals the natural replenishment rate.

What is the difference between exponential and logistic population growth?

Exponential growth (J-curve): unlimited resources allow the population to grow without bound. Logistic growth (S-curve): growth slows as the population approaches carrying capacity (K) due to resource constraints and competition.

What is carrying capacity (K)?

The maximum population size that an environment can sustainably support given the available food, water, shelter, and other resources. When a population exceeds K, mortality rises and/or birth rates fall until it returns to K.

What is the difference between density-dependent and density-independent limiting factors?

Density-dependent factors intensify as population density increases (disease, competition, predation). Density-independent factors affect populations regardless of size (natural disasters, temperature extremes, climate events).

What is the demographic transition model?

A 4-stage model describing how countries shift from high birth/death rates (Stage 1) to low birth/death rates (Stage 4) as they industrialize and develop economically, typically resulting in a stable or declining population.

What is total fertility rate (TFR) and what value indicates replacement level?

TFR = average number of children a woman has in her lifetime. Replacement-level TFR is approximately 2.1 in developed countries (slightly higher in developing countries where child mortality is greater).

What are the three levels of biodiversity?

1. Genetic diversity: variation within a species. 2. Species diversity: variety of species in an area. 3. Ecosystem diversity: variety of habitat types and ecological communities across a region.

What is an invasive species and why are they harmful?

Non-native species introduced to a new ecosystem where they lack natural predators or controls. They outcompete native species, disrupt food webs, and reduce biodiversity. Example: kudzu vine smothering forests in the SE US.

What does HIPPCO stand for in biodiversity loss?

Habitat destruction, Invasive species, Population growth (human), Pollution, Climate change, Overexploitation — the six major human-caused drivers of biodiversity loss worldwide.

What is an endemic species?

A species found exclusively in one specific geographic area and nowhere else in the world (e.g., lemurs in Madagascar). Endemic species are especially vulnerable to extinction because their entire population exists in one place.

What is the difference between habitat fragmentation and habitat destruction?

Habitat destruction eliminates habitat entirely. Habitat fragmentation breaks continuous habitat into smaller, isolated patches — reducing species movement and gene flow, and increasing vulnerable 'edge' habitat that favors generalists over specialists.

What is the difference between a producer, consumer, and decomposer?

Producers (autotrophs) make food via photosynthesis. Consumers (heterotrophs) eat other organisms. Decomposers (fungi, bacteria) break down dead organic matter, recycling nutrients back into the ecosystem.

What is the 10% rule in energy transfer?

Only about 10% of energy stored in one trophic level is transferred to the next. The remaining 90% is lost as heat, movement, and metabolic waste — which is why food chains rarely exceed 4–5 levels.

What is the difference between GPP and NPP?

GPP (Gross Primary Productivity) = total photosynthesis by plants. NPP (Net Primary Productivity) = GPP minus plant respiration. NPP represents the energy actually available to consumers: NPP = GPP − Respiration.

What are the key steps of the nitrogen cycle?

Nitrogen fixation (N₂ → NH₃) → Nitrification (NH₃ → NO₂⁻ → NO₃⁻) → Assimilation by plants → Ammonification (decomposers return N to soil as NH₃) → Denitrification (bacteria release N₂ back to atmosphere).

What is primary succession? Give an example.

Ecological change starting on bare substrate with no soil (e.g., lava flows, retreating glaciers). Pioneer species like lichens and mosses colonize first, slowly building soil that allows more complex communities to establish.

What is a keystone species? Give an example.

A species with a disproportionately large effect on its ecosystem relative to its abundance. Example: sea otters control sea urchin populations — without them, urchins overgrow and destroy kelp forests.

4 major earth systems

lithosphere, biosphere, atmosphere, hydrosphere

difference between weather and climate

weather is short-term (day-to-day), climate is long term (30+ years)

What drives the hydrologic cycle

solar energy and gravity/air

El Niño

El Niño is the warm phase of ENSO (El Niño–Southern Oscillation). Warm Pacific waters shift eastward, disrupting jet streams — causing droughts in Australia/SE Asia and heavy rainfall in western South America and the southern US.

Explain divergent, convergent, and transform plate boundaries.

Divergent: plates move apart, forming mid-ocean ridges. Convergent: plates collide, creating subduction zones and mountains. Transform: plates slide horizontally past each other, causing earthquakes (e.g., San Andreas Fault).

Coriolis effect

Earth's rotation deflects moving air and water — rightward in the Northern Hemisphere, leftward in the Southern. It shapes global wind patterns, ocean gyres, and storm rotation (hurricanes vs. cyclones).