AP Environmental Science Exam Review Flashcards

Nitrogen Cycle

• The atmosphere is the major nitrogen reservoir, existing as N_2 gas (two nitrogen molecules triple-bonded).
• The triple bond is very strong, making it difficult for plants and humans to break naturally.
• Nitrogen fixation relies on specialized bacterial enzymes to break the nitrogen bond and pair it with hydrogen.
• Biological nitrogen fixation:
  • Bacteria live freely in the soil or in symbiotic relationship with plants (e.g., legumes like peas and beans).
  • Rhizobacteria inhabit root nodules and fix nitrogen, converting N_2 to ammonia.
  • Plants receive nitrogen, while bacteria receive sugars from the plant, a mutualistic relationship.
• Synthetic nitrogen fixation: Nitrogen can be synthetically fixed by burning fossil fuels to make fertilizers.
  • Drawback: uses fossil fuels.
  • Overapplication can lead to eutrophication.
• Phosphorus cycle:
  • Slower than the nitrogen cycle due to lack of atmospheric component.
  • Cycles through weathering of rocks, creating phosphates washed into soil and water via runoff.

Crop Rotation

• Crop rotation with legumes enriches soil with nitrogen through nitrogen fixation.
• Legumes' nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, which plants can use.

Trophic Pyramid and the 10% Rule

• The base (producers) contains 100% of the energy in the biome.
• Energy transfer between trophic levels is inefficient; 90% of energy is lost as heat or indigestible biomass.
• Only 10% of energy moves to the next level, impacting population sizes at higher levels.
  • Example: Eagles being few in a large forest due to energy loss at each level.
• Energy loss explained: Organisms use energy for metabolic processes, movement, and respiration, and some biomass is indigestible.
• Implications of the 10% rule:
  • There needs to be 10x more plant bio mass for each level.

Carbon Sequestration

• Carbon sequestration: the act of storing carbon.
  • Old growth forests store carbon in bark, leaves, and roots.
  • Oceans dissolve CO_2, which is taken up by organisms, that die, sink, compress, and form sedimentary rocks.
• Carbon sink: Stores more carbon than it releases.
• Reservoir : Generic term for anything that can hold carbon.
• Soils and wetlands can also sequester carbon when plants die and decompose.

Unit One Review

• Likely topics:
  • Carbon cycle
  • Primary productivity
  • 10% rule
• Recommended album: Women in Music Pt. III by Haim

Biodiversity

• Ecosystem diversity:
  • Variety of ecosystems within a large area.
  • High ecosystem diversity supports more species.
• Species diversity:
  • Number of species in an area (richness) and their distribution (evenness).
  • Benefits: complex food webs, stability.
• Genetic diversity:
  • Variations in genes within a population.
  • Importance: resilience to environmental stressors.
  • Example: Potatoes resistant to blight survive, while cloned potatoes all succumb.

Ecosystem Resilience

• The ability of an ecosystem to return to its original conditions after a disruption.
• High biodiversity helps stabilize ecosystems through repopulation and species redundancy.

Ecosystem Services

• Benefits humans receive from ecosystems.
• Types:
  • Provisioning: products obtained (e.g., lumber).
  • Regulating: benefits from ecosystem processes (e.g., climate regulation).
  • Supporting: essential for other services (e.g., pollination).
  • Cultural: recreational, aesthetic, and educational benefits.

Keystone Species

• Species with disproportionately large impact on their ecosystem relative to their abundance.
• Example: Beavers, which create new ecosystems by building dams.

Unit Two Review

• Must-know concepts: ecosystem services, keystone species, biodiversity.
• Likely FRQ topics: ecosystem services, keystone species, biodiversity as a consequence of human action.
• Recommended album: Bon Iver by Bon Iver

Population Ecology: r-selected vs. k-selected

• K-strategists:
  • Fewer offspring, high parental care (quality over quantity).
  • Slower sexual maturity, longer development.
  • Thrive in stable ecosystems.
• R-strategists:
  • Rapid reproduction, minimal parental care.
  • Many offspring, quick sexual maturity.
  • Favored in rapidly changing ecosystems.

Population Math

• Population Growth Rate (%): ((Crude Birth Rate - Crude Death Rate) / 10)
• Doubling Time (Years): 70 / Growth Rate

Total Fertility Rate (TFR)

• Average number of children a woman will have in her lifetime.
• Factors Increasing TFR:
  • Less education and job opportunities for women.
  • Cultural acceptance of large families in developing areas.
• Replacement Level Fertility: the number of children needed to maintain a stable population.

1. 1 in highly developed countries due to quality healthcare access.

Theory of Demographic Transition

• Stage 1: High birth and death rates (stable population).
• Stage 2: High birth rates, declining death rates (population explosion). Access to health care and clean water starts to increase.
• Stage 3: Declining birth rates, low death rates (slower population growth). Family planning access is important here.
• Stage 4: Low birth and death rates (stable population).

Unit Three Review

• Must-know vocab terms: r-selected, k-selected, TFR, demographic transition.
• Likely FRQ topics:
  • R-selected and k-selected species.
  • Factors that increase or decrease TFR, family planning.
  • Human population and environmental impacts.

Soil: Weathering and Erosion

• Weathering: Breakdown of rocks into smaller pieces.
• Erosion: Movement of sediments from one place to another.

Soil Characteristics

• Permeability: How easily water drains through the soil.
  • Large connected pores (e.g., sandy soil) = high permeability.
• Water Holding Capacity: How much water soil retains.
  • Opposite of permeability.
  • Too sandy = water drains quickly.
  • Too much clay = waterlogged roots.
• Loam = balanced mixture of sand, silt, and clay.
• Nutrient Depletion: When nutrients get leached out with the water.
• Soil Degradation: Loss of soil structure, compaction, and nutrient depletion.
• Nutrient depletion: growing N demanding crops, like corn.

Atmosphere: Common Gases and Important Layers

• Nitrogen (78%) > Oxygen (21%) > Argon > Water Vapor > CO_2
• Troposphere: Lower layer, where weather occurs.
• Stratosphere: Contains the ozone layer that saves us from the sun.

Watershed Pollutants & Solutions

• Cover Crops: Plants used after harvest to absorb nutrients and anchor soil.
• Riparian Buffer: Vegetation alongside streams that catches and absorbs nutrients/sediments.
• Manure Management:
  • Lined manure lagoons pumped out often.
  • Making pellet fertilizer out of manure.
• Tertiary Treatment: Filter systems to grab nitrogen and phosphorus.
• Septic Tank Upgrades: Having a deeper drainage, and making sure to pump it out often.
• Retention Basins: A way to hold and filter the water slowly through plants.

El Niño and La Niña

• El Niño (Little Boy):
  • Weakening/reversal of trade winds.
  • Warm ocean water off the coast of South America.
  • Suppressed upwelling, less productive fisheries.
  • Worse fishing off coast of South America.
• La Niña (Little Girl):
  • Larger than normal conditions (wind carries surface water East to West).
  • Extra cold water and better ocean water off of South America.
• Warm Air Rises:
  • Has less pressure because less atmosphere pushing down on it.

Unit Four Review

• Must-know vocab: weathering, erosion, soil characteristics, watersheds, El Niño/La Niña.
• Likely FRQ topics: Soil, watersheds and their pollutants/solutions, El Niño/La Niña.