Practice Test 8 - DAT Reading Comprehension

20 questions. Answer them in any order, then submit to see your score and every explanation.

The primary purpose of the passage is to:
What is the main purpose of the passage?
**Environmental Process: carbon cycling across reservoirs** Carbon moves among Earth's major reservoirs—atmosphere, biosphere, hydrosphere, and geosphere—through coupled physical, chemical, and biological fluxes. In the atmosphere, carbon is largely present as carbon dioxide (CO $_2$ ), a greenhouse gas that absorbs infrared radiation. Terrestrial plants remove CO $_2$ via photosynthesis (light-driven fixation of CO $_2$ into organic molecules), storing carbon in biomass and soils. In parallel, cellular respiration oxidizes organic carbon back to CO $_2$ , returning it to the atmosphere. The net balance between these processes determines whether an ecosystem is a carbon sink or a carbon source. In the ocean, CO $_2$ dissolves and reacts with water to form carbonic acid, which dissociates into bicarbonate (HCO $_3^-$ ) and carbonate (CO $_3^{2-}$ ). This set of reversible reactions is the carbonate system, and it buffers seawater pH by distributing dissolved inorganic carbon among species. Colder waters dissolve more CO $_2$ ; thus, high-latitude oceans can absorb atmospheric CO $_2$ , while warming reduces solubility. Phytoplankton fix dissolved CO $_2$ into organic matter; when organisms die, a fraction of this carbon sinks as particles in the biological pump, transferring carbon to deeper waters. Some sinking organic matter is remineralized by microbes, producing CO $_2$ at depth; some is buried in sediments, forming long-term geologic storage. Carbonate shells (CaCO $_3$ ) produced by organisms can also sink; however, in deep, high-pressure waters, CaCO $_3$ can dissolve below the carbonate compensation depth (CCD), limiting sedimentary carbonate burial. Over millions of years, tectonics and volcanism return geologic carbon to the atmosphere as CO $_2$ , while chemical weathering of silicate rocks consumes CO $_2$ by forming bicarbonate that is eventually transported to the ocean. Human activities have perturbed these fluxes by moving carbon from the geosphere to the atmosphere through fossil-fuel combustion and land-use change. Elevated atmospheric CO $_2$ increases ocean uptake, but this drives ocean acidification because added CO $_2$ shifts the carbonate system toward more HCO $_3^-$ and fewer CO $_3^{2-}$ ions. Reduced carbonate ion availability can impair calcifying organisms that build shells and skeletons. Meanwhile, warming can weaken ocean uptake by decreasing CO $_2$ solubility and altering circulation that ventilates deep waters. Feedbacks emerge because carbon fluxes respond to climate. For example, thawing permafrost can increase microbial decomposition of previously frozen organic matter, releasing CO $_2$ and methane (CH $_4$ ), another greenhouse gas. Conversely, reforestation can increase biomass carbon storage, but the permanence of that storage depends on disturbance regimes such as fire and drought. Understanding relationships among reservoirs requires tracking both fast biological exchanges and slow geochemical processes. How does increased atmospheric CO $_2$ lead to reduced carbonate ion availability in seawater according to the passage?
It can be inferred from the passage that xerophytes must have a mechanism to...
The author's tone regarding prion diseases can best be described as...
As described in the passage, the 'asthenosphere' is the:
**Medical Innovation: monoclonal antibodies and target specificity** Monoclonal antibodies (mAbs) are engineered immunoglobulins designed to bind a specific epitope on a target molecule. In oncology, many mAbs target cell-surface receptors that drive proliferation, such as HER2 or EGFR. Binding can block ligand-receptor interactions, induce receptor internalization, or recruit immune effector functions via the antibody Fc region, including antibody-dependent cellular cytotoxicity (ADCC). ADCC occurs when Fc receptors on natural killer cells bind the Fc portion of antibodies attached to tumor cells, triggering cytotoxic granule release. Developing a therapeutic mAb begins with identifying a target whose inhibition should impair disease while minimizing harm to normal tissues. Preclinical work evaluates binding affinity (strength of interaction), specificity (preference for the intended target over others), and functional effects in cell assays and animal models. Humanization of antibodies reduces immunogenicity by replacing non-human framework regions while preserving antigen-binding complementarity-determining regions. Even so, anti-drug antibodies can form and reduce efficacy or cause hypersensitivity. Clinical trials measure safety, dosing, and benefit in defined patient populations. Biomarkers can enrich trials by selecting patients whose tumors express the target, improving the chance of response. However, tumors can evolve resistance by mutating the epitope, activating downstream pathways, or reducing antigen expression. Combination therapies may counter resistance but can increase toxicity and cost. What is the relationship between Fc-mediated ADCC and antibody binding to tumor-cell epitopes as described?
From the passage, it can be inferred that the author believes...
It can be inferred that the therapeutic effectiveness of RNAi for a specific disease depends on...
In the context of the passage, 'immunogenicity' refers to the:
The use of sialometry to quantify both unstimulated and stimulated flow rates is a diagnostic tool that directly assesses the functions of which systems described in the passage?
The passage defines 'subduction' as the process where:
The passage presents the overall relationship between an initial stimulus of low blood pressure and the multifaceted response of the RAAS as a:
The author's tone toward the subject of extremophiles can best be described as...
**Environmental Process: trophic cascades in aquatic ecosystems** Aquatic food webs link primary producers (algae and phytoplankton), herbivores (zooplankton), and predators (fish) through energy transfer. A trophic cascade occurs when changes at one trophic level indirectly affect non-adjacent levels. For instance, adding piscivorous fish (fish-eating predators) can reduce planktivorous fish that consume zooplankton. With fewer planktivores, zooplankton populations may increase, intensifying grazing on phytoplankton and lowering algal biomass. Algal biomass influences water clarity and oxygen dynamics. Dense algal blooms can shade submerged vegetation and, when decomposed by microbes, increase biochemical oxygen demand, potentially leading to hypoxia. Nutrient inputs of nitrogen and phosphorus often stimulate algal growth, but food-web structure modulates whether nutrients translate into blooms. Therefore, lake management sometimes combines nutrient reduction with biomanipulation—altering fish communities—to improve water quality. However, cascades are context-dependent. If zooplankton are limited by refuge availability or if algae are inedible due to toxins or size, increased zooplankton may not reduce blooms. Additionally, predators can have non-consumptive effects by altering prey behavior, changing grazing patterns without large changes in prey abundance. How does adding piscivorous fish lead to improved water clarity according to the passage?
The passage implies that the primary relationship between bioaugmentation and the indigenous microbial community is one of:
The phrase 'surface topography' in this passage refers to the:
**Medical Innovation: antibiotic stewardship and resistance selection** Antibiotics impose selective pressure on bacterial populations. Within a population, some cells may carry resistance genes due to mutation or horizontal gene transfer via plasmids, transposons, or bacteriophages. When an antibiotic is administered, susceptible bacteria are killed or inhibited, while resistant bacteria survive and replicate, increasing the frequency of resistance. This is a textbook example of natural selection acting on heritable variation. Resistance mechanisms include enzymatic drug inactivation (e.g., β-lactamases), target modification (altered ribosomal binding sites), reduced permeability, and efflux pumps that export drugs. Incomplete courses, unnecessary prescribing, and broad-spectrum use can intensify selection by exposing bacteria without fully eradicating them or by disrupting normal microbiota that compete with pathogens. Hospitals are high-risk environments because dense patient populations and invasive devices facilitate transmission. Antibiotic stewardship programs aim to optimize drug choice, dose, and duration. Rapid diagnostics can narrow therapy by identifying pathogens and susceptibility, reducing broad-spectrum exposure. Infection control measures—hand hygiene, isolation, environmental cleaning—reduce spread of resistant strains. The goal is not to eliminate antibiotic use, but to preserve effectiveness by slowing resistance evolution. What link does the passage establish between broad-spectrum antibiotic use and increased resistance prevalence?
The passage suggests that the inflammatory response observed in necrosis is causally linked to the:
The author's tone in this passage can best be described as...

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