AP Environmental Science:: Unit 5 - Landwater

The Green Revolution, a major mid-20th-century shift in global agricultural practice, is best described as an effort to significantly increase crop yields primarily through:

- **A)** Exclusively expanding the total land area under cultivation, with no meaningful role for any change in seed variety, fertilizer, irrigation, or pesticide use
- **B)** The combined introduction of high-yield crop varieties (bred specifically for greater productivity), synthetic fertilizers, chemical pesticides, and expanded irrigation - this combination dramatically increased global food production per unit of cultivated land (helping avert the kind of Malthusian food-scarcity crisis discussed in an earlier unit) but has also been associated with significant environmental trade-offs, including increased fertilizer/pesticide runoff pollution and greater dependence on fossil-fuel-intensive agricultural inputs
- **C)** A complete abandonment of synthetic fertilizer and pesticide use in favor of exclusively organic farming methods across the entire globe
- **D)** A shift toward farming only within densely-forested tropical regions, with no meaningful application of this shift to any other biome or region

Synthetic nitrogen fertilizer, a central input of Green Revolution-style industrial agriculture (discussed above), can contribute to a significant water pollution problem downstream of heavily fertilized farmland primarily through the process of:

- **A)** Bioaccumulation, a concept introduced in an earlier unit describing toxin build-up within a single organism's own body tissue, rather than accurately describing fertilizer runoff's own distinct water pollution mechanism
- **B)** Biomagnification, a concept introduced in an earlier unit describing toxin concentration at higher trophic levels, rather than accurately describing fertilizer runoff's own distinct water pollution mechanism
- **C)** A process that has no meaningful, describable relationship to nutrient runoff, algae, or water pollution of any kind
- **D)** Nutrient runoff, in which excess fertilizer not absorbed by crops washes off farmland (especially after heavy rainfall) into nearby streams, rivers, and eventually lakes or coastal ocean waters - this excess nutrient input can trigger eutrophication, an process covered in much greater depth in a later unit on aquatic pollution, in which excessive algae growth is fueled by the added nutrients, ultimately depleting the water body's dissolved oxygen as that excess algae later dies and decomposes

Monoculture agriculture (discussed in an earlier unit's coverage of biodiversity threats) is also closely associated with a heavier reliance on chemical pesticides, primarily because:

- **A)** A large, uniform planting of a single crop species/variety provides an unusually abundant, concentrated food source for any pest species well-adapted to that specific crop, allowing pest populations to grow and spread unusually quickly across the entire uniform planting - a diverse planting (intercropping several different crop species together, discussed further below) instead tends to naturally limit a given pest's ability to spread as easily, since suitable host plants are more scattered and interspersed with non-host plants
- **B)** Monoculture planting has no meaningful, describable relationship to pest population size, spread, or pesticide reliance of any kind
- **C)** A diverse, multi-crop planting is, in fact, always more vulnerable to pest outbreaks than a single-crop monoculture planting, the general opposite of this question's own actual, well-established typical relationship
- **D)** Monoculture farming always completely eliminates any possibility of a pest outbreak occurring at all, contradicting monoculture's own actual, well-established increased vulnerability to pest outbreaks discussed in an earlier unit

Pesticide resistance, an increasingly significant agricultural challenge, develops in a pest population over time primarily through the process of:

- **A)** A pesticide directly and permanently altering every individual pest's own genetic makeup upon exposure, rather than accurately describing how pesticide resistance actually develops within a population over successive generations
- **B)** A process that has no meaningful, describable relationship to natural selection, genetic variation, or pesticide application of any kind
- **C)** Natural selection acting on naturally-occurring genetic variation already present within the pest population - repeated pesticide application kills off the more pesticide-susceptible individuals, while any individuals that happen to already carry a naturally-occurring resistance-conferring gene variant survive and reproduce, gradually increasing the resistant gene variant's overall frequency within the population over successive generations, until the pesticide eventually becomes considerably less effective against that now largely-resistant population
- **D)** A pest population's total genetic diversity always decreasing to zero upon a single pesticide application, rather than accurately describing how resistance actually develops gradually over multiple generations of selection

Integrated pest management (IPM), an increasingly favored alternative/complementary approach to relying on chemical pesticides alone, is best described as a strategy that:

- **A)** Relies exclusively on a single chemical pesticide applied at maximum possible strength and frequency, with no meaningful use of any non-chemical pest control method
- **B)** Combines multiple complementary pest-control strategies - such as biological control (introducing or encouraging a pest's natural predators), crop rotation, resistant crop varieties, and targeted, more limited pesticide use only when genuinely needed (rather than on a fixed, routine schedule) - in order to keep pest populations below an economically damaging threshold while minimizing both pesticide resistance development (discussed above) and pesticide-related environmental harm
- **C)** A pest-control approach that has no meaningful, describable relationship to biological control, crop rotation, or targeted pesticide application of any kind
- **D)** A strategy that applies only to organic farming operations, with no meaningful applicability to any conventional, non-organic farming operation

Crop rotation, an agricultural practice in which different crop species are planted in a sequential rotation on the same field across different growing seasons (rather than planting the identical crop repeatedly), provides agricultural benefits primarily by:

- **A)** Permanently depleting the soil of all its nutrients at a faster rate than continuous monoculture planting of a single crop would, the general opposite of crop rotation's own actual, well-established soil-nutrient benefit
- **B)** Increasing, rather than decreasing, a field's vulnerability to the pest and disease buildup associated with continuous single-crop planting, the general opposite of crop rotation's own actual, well-established pest-management benefit
- **C)** A practice that has no meaningful, describable relationship to soil nutrients, pest cycles, or agricultural sustainability of any kind
- **D)** Interrupting the life cycle of pests and diseases that are specifically adapted to a single crop species (since a pest specialized on last season's crop finds a different, unsuitable crop planted this season), and by varying the specific nutrients drawn from (and, in the case of a nitrogen-fixing legume crop planted in rotation, sometimes even added back into) the soil across the different crops in the rotation - both effects help reduce the reliance on chemical pesticides and synthetic fertilizer that continuous monoculture planting (discussed above) tends to require

Desertification, the process by which productive land in a dryland region becomes progressively degraded into a considerably less productive, desert-like state, is most commonly driven by a combination of natural drought conditions and:

- **A)** Unsustainable human land-use practices such as overgrazing by livestock (removing vegetation faster than it can naturally regrow), deforestation, and poor irrigation practices (which can sometimes cause soil salinization, discussed further below) - these human pressures can push an already-fragile dryland ecosystem past a tipping point from which natural recovery becomes considerably more difficult, even once a drought period itself eventually ends
- **B)** A process that has no meaningful, describable relationship to overgrazing, deforestation, or irrigation practices of any kind
- **C)** Excessive, rather than insufficient, vegetation cover, the general opposite of desertification's own actual, well-established association with vegetation loss
- **D)** A phenomenon that occurs at a perfectly uniform rate across every dryland region on Earth, entirely independent of any specific local human land-use practice

Overgrazing, a significant contributor to desertification (discussed above), occurs when:

- **A)** Livestock are prevented from grazing on a given parcel of land for an extended period of time, the general opposite of overgrazing's own actual, well-established definition
- **B)** A parcel of land supports a smaller number of livestock than its own natural carrying capacity (a concept introduced in an earlier unit) could otherwise sustainably support
- **C)** Livestock consume vegetation on a parcel of land faster than that vegetation can naturally regrow, which is conceptually the same basic carrying-capacity overshoot dynamic introduced in an earlier unit's coverage of wild animal populations, just applied here specifically to a human-managed livestock grazing context - persistent overgrazing can strip away protective vegetation cover, leaving the underlying soil considerably more exposed and vulnerable to erosion, potentially triggering the desertification process discussed above
- **D)** A phenomenon that has no meaningful, describable relationship to livestock, vegetation, or carrying capacity of any kind