APES Exam Review Flashcards - Units 1-5

APES Exam Review 2025: Units 1-5

• Unit 9:

  • Environmental Solutions: Comprises 15-20% of the exam.

  • Review using Unit 9 Review Videos or the URP.

• Unit 5:

  • Land Use: Accounts for 10-15% of the exam and has appeared on every FRQ from 2021 to 2024.

  • Review using Unit 5 Review Videos or the URP.

• Math Review:

  • Essential for 11-13% of the exam.

  • Predictable content; search "APES Math Review" for a 20-minute tutorial.

  • Practice problems are crucial.

Focus for Units 1-5

• Topics/Terms Often Missed:

  • Address most confusing concepts.

• FRQ Writing Essentials:

  • Learn must-know vocabulary terms.

• Tricky FRQ Questions:

  • Review tricky FRQ questions from recent exams for each unit.

Unit 1: Ecosystems

Carbon Cycle: Ocean & Atmosphere

• Direct Exchange: CO_2 moves directly between the atmosphere and the ocean via dissolving.

  • Increasing atmospheric CO2 increases ocean CO2, leading to ocean acidification.

• Algae & Phytoplankton:

  • Remove CO_2 from the ocean and atmosphere through photosynthesis.

• Coral, Mollusks, & Zooplankton:

  • Remove CO2 to create calcium carbonate (CaCO3) exoskeletons.

• Sedimentation:

  • Calcium carbonate precipitates as sediment on the ocean floor.

• Burial:

  • Over time, pressure compresses carbon-containing sediments into sedimentary rock (limestone, sandstone).

  • This forms a long-term carbon reservoir.

Nitrogen Fixation

• Biotic Fixation: Bacteria in soil or plant root nodules convert N2 into ammonia (NH3).

  • N2 gas is converted into biologically available NH3 (ammonia) or NO_3^− (nitrate).

• Rhizobacteria:

  • Live in legume root nodules (peas, beans).

  • Fix nitrogen in exchange for amino acids from the plant (mutualism).

FRQ Example – Crop Rotation

• (e) Question: Describe an advantage of crop rotation using legumes on soil fertility.

• Answer:

  • Improved nitrogen fixation in the soil reduces the need for nitrogen-based fertilizers.

Trophic Pyramid

• Energy Transfer:

  • 10% of energy passes from one trophic level to the next.

  • 90% is lost as heat or indigestible biomass.

• Explanations/Relations:

  • Explains population sizes at different trophic levels.

  • Relates to what happens when photosynthesis is limited.

  • Explains biomagnification.

  • Relates to why meat production requires more land than plant production.

• Energy levels: 100%, 10%, 1%, 0.01%

Unit 1: Must-Know Vocab & FRQ Topics

• Vocabulary:

  • Competition

  • Nutrient availability

  • Carbon sequestration

  • Nitrogen fixation

  • Infiltration vs. runoff

  • Primary productivity

  • Trophic levels/10% rule

  • Energy transfer

• Likely FRQ Topics:

  • 1.4 - Carbon Cycle

  • 1.8 - Primary Productivity

  • 1.9 - Trophic Levels & 10% Rule

Unit 2: Biodiversity

Biodiversity Basics

• Definition: Diversity of life forms in an ecosystem.

• Levels:

  • Genetic Diversity: Differences in genes among individuals within a population.

  • Species Diversity: Number of different species in an ecosystem and the balance of population sizes.

  • Ecosystem Diversity: Number of different habitats available in a given area.

• Higher biodiversity = higher ecosystem/population health.

Genetic Diversity

• Present in all populations due to:

  • Random mutations in DNA copying

  • Recombination of chromosomes during sexual reproduction.

• Benefit:

  • The more genetic diversity, the better the population can respond to environmental stressors (drought, disease, famine).

  • Increases the chance that some individuals have traits that allow them to survive environmental stressors.

Ecosystem Resilience

• Resilience: The ability of an ecosystem to return to its original condition after a major disturbance (wind storm, fire, flood, clear-cutting, etc.).

• Higher species diversity = higher ecosystem resilience

• High species diversity increases the likelihood that some plant species will survive, stabilizing the ecosystem by providing food, habitat, anchoring soil, and cycling energy.

FRQ Example - Species Richness

• Question: Explain how the species richness of an ecosystem influences its response to environmental stressors.

• Answer: An ecosystem with greater species richness/diversity is more resilient/resistant to environmental stressors because some species will survive, helping to restore/stabilize the ecosystem.

Ecosystem Services

• Definition: Goods and services provided by natural ecosystems that are beneficial to humans (often monetarily or life-sustaining).

• Types:

  • Provisioning: Goods taken directly from ecosystems (wood, paper, food).

  • Regulating: Natural ecosystems regulate and stabilize climate, air quality, water quality, and soil.

  • Supporting: Natural ecosystem processes that sustain ecosystems and support life.

  • Cultural: Money generated by recreation (parks, camping, tours) or scientific knowledge.

FRQ Example - Asian Carp

• Question: Describe one impact the introduction of Asian carp could have on the ecosystem services provided by the Great Lakes region.

• Answer:

  • Possible answers include (but are not limited to):

    • Decreased fishing due to carp outcompeting native fish species.

    • Decreased drinking water quality as carp displace filter feeders like native mussels.

    • Decreased recreational opportunities due to carp interfering with activities.

Keystone Species

• Definition: A species that has a disproportionately large effect on its environment relative to its abundance.

• Characteristics:

  • Increases ecosystem stability OR reduces ecosystem stability when absent.

• Example: Beavers

  • Beaver dams transform the environment, creating habitats, maintaining habitat stability by reducing floods, removing water-borne pollutants, trapping sediments (creating habitats and reducing turbidity), and reducing erosion of stream banks.

Unit 2: Must-Know Vocab & FRQ Topics

• Vocabulary:

  • Resilience

  • Genetic/species/ecosystem diversity

  • Ecosystem service

  • Range of tolerance

  • Adaptation

  • Keystone Species

• Likely FRQ Topics:

  • 2.1 - Biodiversity

  • 2.2 - Ecosystem Services

  • 2.7 - Keystone Species

Unit 3: Populations

Quality vs. Quantity

• K-selected - “quality”

  • Few offspring, heavy parental care to protect them.

  • Generally have fewer reproductive events than r-strategists.

  • Ex: most mammals, birds.

  • Long lifespan, long time to sexual maturity = low biotic potential = slow pop. growth rate.

  • More likely to be disrupted by env. change or invasives.

• R-selected - “quantity”

  • Many offspring, little to no care.

  • May reproduce only once, but generally reproduce many times throughout lifespan.

  • Ex: insects, fish, plants.

  • Shorter lifespan, quick to sexual maturity = high biotic potential = high pop. growth rate.

  • More likely to be invasive.

  • Better suited for rapidly changing env. conditions.

Population Growth Math

• Growth Rate (r): % increase in a population (usually per year).

• Crude Birth Rate & Crude Death Rate (CBR & CDR): Births & deaths per 1,000 people in a population.

  • Ex: Global CBR = 20 & CDR = 8

• Calculating Growth Rate (r): r = \frac{CBR - CDR}{10}

  • Divide by 10 because CBR & CDR are per 1,000 and growth rate is % or per 100

  • Growth rate always expressed as %

Doubling Time (Rule of 70)

• The time it takes (in years) for a population to double is equal to 70 divided by the growth rate.

• Formula: Doubling Time = \frac{70}{Growth Rate}

• Ex: Global growth rate = 1.2% \frac{70}{1.2} = 58.3 years. The global population will double in 58.3 years.

FRQ Example - Doubling Time

• (ii) Question: Based on Charlotte's 2019 growth rate of 1.88%, calculate the year when the population of Charlotte will double, assuming the growth rate stays the same. Show your work.

• Answer:

  • One point for the correct setup to calculate the year the population of Charlotte will double:

    • Doubling time = \frac{70}{1.88} = 37 years + 2019

  • One point for the correct calculation year the population of Charlotte will double:

    • 2056

TFR & Infant Mortality

• Total Fertility Rate (TFR): avg. number of children a woman in a population will bear throughout her lifetime.

  • Higher TFR = higher birth rate, higher pop. growth rate (generally).

• Replacement Level Fertility: the TFR required to offset deaths in a pop. and keep pop. size stable.

  • About 2.1 in developed countries (replace mom & dad).

  • Higher in less developed countries due to higher infant mortality.

• Infant Mortality Rate (IMR): number of deaths of children under 1 year per 1,000 people in a pop.

  • Higher in less developed countries due to lack of access to: health care, clean water, enough food.

  • Higher IMR = higher TFR, due to families having replacement children.

Stages & Development

• 1 = pre-industrial

• 2 = developing

• 3 = Developed

• 4 = Highly developed

Unit 3: Must-Know Vocab & FRQ Topics

• Vocabulary:

  • r vs. K-selected

  • Generalist vs. specialist

  • Biotic potential

  • Carrying capacity

  • Age cohorts (0-14, 15-44, 45+)

  • TFR, affluence, female education

  • Rule of 70 → \frac{70}{r} = 2x time (yrs.)

  • TDT (Phase 1, 2, 3, 4)

• Likely FRQ Topics:

  • 3.2 - r-selected vs. K-selected

  • 3.7 - TFR

  • 3.9 - Theory of Dem. Transition

Unit 4: Earth Systems

Weathering

• Definition: Breakdown of rocks into smaller pieces

  • Physical (wind, rain, freezing/thawing of ice)

  • Biological (roots of trees crack rocks)

  • Chemical (acid rain, acids from moss/lichen)

• Weathering of rocks = soil formation

  • Broken into smaller and smaller pieces

  • Carried away and deposited by erosion

Erosion

• Transport of weathered rock fragments by wind and rain

• Carried to new location and deposited (deposition)

Pore space, Permeability, and H_2O Holding Capacity

• Permeability: how easily water drains through a soil

• Pore space: larger, connected pore spaces = greater permeability (avoid the term “porosity”, it’s counter-intuitive)

• H_2O Holding Capacity: how well water is retained, or held by a soil

  • More permeable = lower H_2O holding capacity

  • Inverse relationship between permeability and H_2O holding capacity

Effect on Soil Fertility

• Soil that is too sandy (too permeable) drains water too quickly for roots + dries out

• Clay-heavy soil doesn’t let H_2O drain to roots, or waterlogs (suffocating them)

• Ideal soil for most plant growth is loam, which balances porosity or drainage, with H_2O holding capacity

Soil Degradation

• Definition: The loss of the ability of soil to support plant growth

• Loss of Topsoil: tiling (turning soil for ag.) + loss of vegetation disturb soil and make it more easily eroded by wind and rain

  • Loss of top soil dries out soil, removes nutrients + soil organisms that recycle nutrients

• Compaction: compression of soil by machines (tractors, bulldozers, etc.), grazing livestock, and humans reduces ability to hold moisture

  • Dry soil erodes more easily

  • Dry soil supports less plant growth, less root structure, leading to more erosion

• Nutrient Depletion: repeatedly growing crops on the same soil removes key nutrients (N, P, K, Na, Mg) over time

  • Reduces ability to grow future crops

Gasses of Earth’s Atmosphere

• Nitrogen ~ 78%

  • Mostly in the form of N_2 (unuseable to plants without being fixed)

• Oxygen ~ 21%

  • Produced by photosynthesis in plants & needed for human/animal respiration

• Argon ~ 0.93%

  • Inert, noble gas

• CO_2 ~ 0.04%

  • Most important GHG; leads to global warming

  • Removed from atm. by photosynthesis

• Water Vapor ~ 0-4%

  • Varies by region & conditions; acts as a temporary GHG, but less concerning than CO_2

  • Quickly cycles through atm

Characteristics of Layers

• Troposphere: Tropo = change (weather occurs here)

  • 0-16 km, most dense due to pressure of other layers above it

  • Most of the atmosphere’s gas molecules are found here

  • Ozone (O_3) in the troposphere is harmful to humans (respiratory irritant) & damages plant stomata, and forms smog

• Stratosphere: “S” for second - 16-60 km; less dense due to less pressure from layers above

  • Thickest O_3 layer is found here; absorbs UV-B & UV-C rays which can mutate DNA of animals (cancer)

• Mesosphere: Meso = for middle; 60-80 km, even less dense

• Thermosphere: Therm = hottest temp;

  • absorbs harmful X-rays & UV radiation

  • charged gas molecules glow under intense solar radiation producing northern lights (aurora borealis)

• Exosphere: Outermost layer where atm. merges with space

Solutions to Watershed Pollutants

• Riparian buffers

• Enhanced nutrient removal.

• Animal manure management

• Cover crops

• Septic tank upgrades

• Drainfield

Normal Year

• Trade winds blow eq. water W ← E

• Cool H_2O upwelled off coast of SA (cool temp + good fi$herie$)

• Warm eq. current brings heat & precip. to Australia & SE Asia

• High pressure in east pacific (SA)

• Low pressure in west pacific (Australia & SE Asia)

El Niño

• Trade winds weaken, then reverse (W → E)

• Warm eq. current brings heat & precip. to Americas (N & S)

• Suppressed upwelling off SA coast (damaging fi$herie$)

• Cooler, drier conditions in Australia & SE Asia

• H pressure in west pacific (Australia & SE Asia)

• L pressure in east pacific (SA)

La Niña

• Stronger than normal trade winds (W ← ← ← E)

• Increased upwelling off SA coast brings cooler than normal conditions, extra good fi$herie$

• Warmer & rainier than normal in Australia & SE Asia

Effects of El Niño

• Suppressed upwelling & less productive fisheries in SA

• Warmer winter in much of N America

• Increased precip & flooding in Americas (W coast especially)

• Drought in SE Asia & Australia

• Decreased hurricane activity in the Atlantic ocean

• Weakened monsoon activity in India & SE Asia

Effects of La Niña

• Stronger upwelling & better fisheries in SA than normal

• Worse tornado activity in US & Hurricane activity in Atlantic

• Cooler, drier weather in Americas

• Rainier, warmer, increased monsoons in SE Asia

Unit 4: Must-Know Vocab & FRQ Topics

• Vocabulary:

  • Permeability

  • Soil texture (sand, silt, clay %)

  • Stratosphere vs. troposphere

  • Trade winds & westerlies

  • Albedo

  • Rain Shadow Effect

  • Weathering vs. erosion

  • El Nino/La Nina

• Likely FRQ Topics:

  • 4.3 - Soil

  • 4.6 - Watersheds (especially pollutants & solutions)

  • 4.9 - El Nino & La Nina

Unit 5: Land Use

Direct Effects of Clearcutting

• Soil Erosion

  • Caused by loss of stabilizing root structure

  • Removes soil organic matter & nutrients from the forest

  • Deposits sediments in local streams

    • Warms water & makes it more turbid (cloudy)

• Increased soil & stream temp.

• Flooding & Landslides

  • Loss of tree shade increases soil temperature

    • Soil has lower albedo than leaves of trees

  • Loss of tree shade along rivers & streams warms them

  • Logging machinery compacts soil

  • Increased sunlight dries out soil

  • Loss of root structure = erosion of topsoil & O horizon

    • All of these factors decrease H_2O holding capacity of soil causing flooding & landslides

GMOs

• GMOs: Genetically modified crops have genes for drought tolerance, pest resistance, faster growth, and larger fruit/grain

• Pros:

  • Increases profitability with fewer plants lost to drought, disease, or pests + larger plant size + yield/acre

• Cons:

  • GMO crops are all genetically identical so gen. diversity is decreased and susceptibility to diseases or pest is increased

    • Ex: Bt corn has been modified with a gene from soil bacteria (Bacillus thuringiensis) to produce a protein that kills many different corn pests

Synthetic Fertilizer

• Shift from organic fertilizers (like manure and compost) to synthetic fertilizers (man-made ammonium, nitrate, phosphate)

• Pros:

  • Increases yield and profits with more key nutrients needed for plant growth (N, P, K) added to the soil

• Cons:

  • Excess nitrate, phosphate are washed off fields and into nearby waters where they cause eutrophication (algae blooms)

  • Require FFs for production, releasing CO_2 (climate change)

Irrigation

• Drawing water from the ground or nearby surface waters and distributing it on fields to increase plant growth

• Pros:

  • Make agriculture possible in many parts of the world that are naturally too dry (don’t receive enough rain)

• Cons:

  • Can deplete groundwater sources, especially aquifers

  • Over watering can drown roots (no O_2 access) and cause soil salinization (increase salt level in soil)

Pesticides

• Increase in use of synthetic pesticides - chemicals sprayed on crops that kill weeds, insects, rodents and other pests that eat or damage crops

• Pros:

  • Increases yield and profits with fewer plants lost to pests

• Cons:

  • Can wash off crops in runoff and kill or harm non-target species in local soil or waters (bees especially)

    • Ex: DDT thinned shells of bird eggs, especially eagles

    • Atrazine turns amphibians and fish intersex

Mining Basics

• Ore: commercially valuable deposits of concentrated minerals that can be harvested and used as raw materials

• Metals: elements that conduct electricity, heat, and have structural properties for building (found within ores)

• Reserve: The known amount of a resource left that can be mined. Usually measured in years left of extraction.

• Overburden: Soil, vegetation, & rocks that are removed to get to an ore deposit below

• Tailings & slag: leftover waste material separated from the valuable metal or mineral within ore (often stored in ponds @ mine site)

Environmental Impacts of Mining

• Acid mine drainage: rainwater leaks into abandoned mine tunnels & mixes with pyrite, forming sulfuric acid

  • Rainwater carrier sulfuric acid into nearby streams, or infiltrates ground water

  • Lowers pH of water, making toxic metals like mercury & aluminum more soluble in water sources (killing aquatic org.)

• Methane Release: coal mining releases methane gas (CH_4) from rock around coal

  • Vented out of mine to prevent explosion & continues seeping out after mine closes

  • GHG → climate change

• Topsoil erosion

• Habitat loss

• Increased stream turb.

• PM Release: coal mining especially, releases lots of soot and other particulates that can irritate human & animal lungs

Env. Consequences of urban runoff

• Decreased infiltration (groundwater recharge)

• Rain washes pollutants into storm drains & into local surface waters:

• Pollutants & effects

  • Salt (plant & insect death)

  • Sediment (turbidity)

  • Fertilizer (eutrophication, algae bloom)

  • Pesticides (kill non target species)

  • Oil & gasoline (suffocate fish/kill aq. insects)

Solution: Permeable Pavement

• Specially designed to allow stormwater to infiltrate & recharge ground water

• Decreases runoff, decreasing pollutants carried into storm drains & into local surface water

• Decreases likelihood of flooding during heavy rainfall

• More costly than traditional pavement

Solution: Rain Garden

• Gardens planted in urban areas, especially surrounding a storm drain

• Decreases runoff by allowing it to soak into garden soil surrounding storm drain

• Decreases likelihood of flooding during heavy rainfall

• Creates hab. for pollinators, sense of place & stores CO_2

Practice FRQ

• (ii) Question: Describe one way that land use practice at location X in the diagram could contribute to the dead zone in the Gulf of Mexico. (agriculture)

• (iii) Question: Describe one way that urban areas in the Mississippi River watershed could contribute to the dead zone in the Gulf of Mexico.

FRQ Example - ANSWER

• (ii) Answer:

  • Fertilizer used on croplands is washed into the streams and rivers in the watershed and feeds the growth of algae once it reaches the Gulf.

  • Concentrated animal feeding operations generate large amounts of organic wastes that can move into streams and rivers, feeding the growth of algae once it reaches the Gulf.

  • Treated or untreated (overflows) sewage released from wastewater treatment plants feeds the growth of algae once it reaches the Gulf.

• (iii) Answer:

  • Wastewater treatment facilities in urban areas may release nutrients in treated wastewater and/or overflows, with this effluent flowing into the Gulf.

  • Impervious surfaces in urban areas can increase the movement/runoff of lawn fertilizers or high-phosphate detergents that move onto pavement areas and flow into the Gulf.

IPM Basics

• Using a variety of pest control methods that minimize env. disruption and pesticide use

• Crop rotation - disrupts pest food source (no food when eggs hatch)

• Intercropping - reduces pest habitat/food source

• Biocontrol (Bringing in a natural predator or parasite to control the pest)

• Researching & monitoring pests and targeting methods to specific pest life cycles

Windbreaks

• Using trees or other plants to block the force of the wind from eroding topsoil

• Can be used as a source of firewood, fruit (income)

No Till

• Leaving leftover crop remains in soil instead of tilling under

• Adds org. matter to soil (nutrients, soil cover, moisture)

• Prevents erosion from loosened soil

Strip Cropping

• Another name for intercropping

• Alternating rows of dense crops (hay, wheat) with rows of less dense crops (corn, soy, cotton) to prevent runoff from eroding soil from less dense rows of

  • crops

• Can provide habitat for pollinators & other species

Improving Soil Fertility

• Replanting same crops continuously depletes soil of the same nutrients Methods of restoring nutrient levels in the soil (N, P, Ca, Mg)

• Crop Rotation

  • Crop rotation can allow soil to recover from nitrogen-demanding crops like corn

  • Peas/beans (legumes) have nitrogen fixing bacteria in their root nodules that can return nitrogen to the soil

Practice FRQ

• (ii) Question: Propose one reasonable method, other than crop rotation, to reduce the use of pesticides in agricultural practices while still maintaining a high crop yield.

FRQ Example - Answer

• (ii) Answer:

  • Use integrated pest management to control the insect crop pest.

  • Use a method of pest control that employs a variety of biological, physical, and

  • chemical methods to control the insect crop pest.

  • Reduce stubble/crop residues in fallow fields that can harbor the insect crop pest.

  • Apply the pesticide when the insect crop pest is most susceptible.

  • Use intercropping rather than a monoculture to reduce the amount of habitat for the pests.

  • Use pest-resistant genetically modified organisms.

Unit 5: Must-Know Vocab & FRQ Topics

• Vocabulary:

  • Clearcutting, selective cutting

  • GMOs, Pesticides, Irrigation, Fertilizers

  • Soil erosion (+solutions)

  • Crop rotation

  • IPM

  • Urban runoff (+ solutions)

  • Sustainable ag.

  • Meat production, CAFOs

• Likely FRQ Topics:

  • 5.2 - Clearcutting

  • 5.3 & 5.4 - Green Revolution & Impacts of Agriculture

  • 5.13 - Reducing Urban Runoff

  • 5.15 - Sustainable Agriculture

  • 5.9 - Mining