1.
What drives the movement of elements in geochemical cycles?
Correct Answer
A. Solar energy
Explanation
Solar energy is a primary driver of the movement of elements in geochemical cycles. It powers processes like photosynthesis, evaporation, and convection currents in the atmosphere and oceans, which are crucial for the cycling of elements such as carbon, nitrogen, and water across different parts of the Earth's system (biosphere, atmosphere, hydrosphere, and lithosphere). While gravity, plate tectonics, and human activity also influence these cycles, solar energy is fundamental to driving the global movement and transformation of elements.
2.
Which cycle involves the transformation of nitrogen gas into usable forms for organisms?
Correct Answer
B. Nitrogen cycle
Explanation
The Nitrogen cycle transforms atmospheric nitrogen (N2) into ammonia (NH3), nitrates (NO3-), and nitrites (NO2-) that organisms can utilize. Nitrogen fixation, either biologically by diazotrophs (nitrogen-fixing bacteria and archaea) or abiotically (through lightning and industrial processes), converts N2 into ammonia. Nitrification by soil bacteria then turns ammonia into nitrites and nitrates, which plants can absorb. This cycle is crucial for synthesizing proteins and nucleic acids in living organisms.
3.
In the carbon cycle, what is the primary process by which carbon dioxide is removed from the atmosphere?
Correct Answer
C. pHotosynthesis
Explanation
Photosynthesis primarily removes carbon dioxide from the atmosphere. This process, carried out by plants, algae, and cyanobacteria, captures CO2 and sunlight to produce oxygen and glucose, a simple sugar that serves as an energy source for the plant. This not only reduces atmospheric CO2 levels but also is the basis for the carbon cycle, influencing climate and the energy flow through ecosystems.
4.
Which element is cycled through the environment primarily by the process of weathering and erosion?
Correct Answer
D. pHospHorus
Explanation
Phosphorus is cycled through weathering and erosion of rocks, which releases phosphate ions into the soil. Plants absorb these ions, which are then transferred through the food chain. When organisms die, decomposers return phosphorus to the soil, and it can also end up in water bodies, where it supports aquatic life. Unlike other cycles, the phosphorus cycle does not have a significant atmospheric component, making it primarily a terrestrial and aquatic cycle.
5.
How does human activity impact the nitrogen cycle?
Correct Answer
D. All of the above
Explanation
Human activity significantly impacts the nitrogen cycle, mainly through the use of synthetic nitrogen fertilizers, which increase nitrogen availability in the soil beyond natural levels. This can lead to nitrogen runoff into water bodies, causing eutrophication and dead zones. Burning fossil fuels releases nitrogen oxides into the atmosphere, contributing to smog and acid rain, and extensive agriculture practices release ammonia into the air, altering biodiversity and ecosystem structure.
6.
What is the main reservoir of carbon in the carbon cycle?
Correct Answer
B. Oceans
Explanation
Oceans are the main carbon reservoir in the carbon cycle, storing about 50 times more carbon than the atmosphere. They absorb CO2 directly from the atmosphere and through the biological pump, where phytoplankton convert CO2 into organic carbon, part of which sinks to the ocean floor. This process regulates atmospheric CO2 levels and, consequently, Earth's climate.
7.
The movement of water from the surface of the Earth to the atmosphere and back is known as the...?
Correct Answer
C. Hydrologic cycle
Explanation
The hydrologic cycle describes water's continuous movement through evaporation, transpiration, condensation, precipitation, and runoff. This cycle is essential for distributing heat around the globe, supporting life, and shaping weather patterns. It also plays a critical role in other geochemical cycles by transporting nutrients and chemicals.
8.
Which cycle is essential for the synthesis of ATP in living organisms?
Correct Answer
C. pHospHorus cycle
Explanation
The Phosphorus cycle is crucial for ATP synthesis, the molecule responsible for energy transfer within cells. Phosphorus, in the form of phosphate, is a component of ATP, as well as DNA and RNA, making it essential for energy storage and genetic information transfer in all living organisms.
9.
In which form do plants primarily absorb nitrogen?
Correct Answer
C. Nitrates (NO₃⁻)
Explanation
Plants absorb nitrogen primarily as nitrates (NO3-), the end product of the nitrification process. This form of nitrogen is more easily assimilated by plants compared to other forms, such as ammonium (NH4+) or nitrogen gas (N2), making it crucial for plant nutrition and, subsequently, for the diet of herbivores and omnivores.
10.
What role do decomposers play in the nitrogen cycle?
Correct Answer
C. Release nitrogen from organic matter
Explanation
Decomposers, such as bacteria and fungi, release nitrogen from organic matter by breaking down the complex proteins, nucleic acids, and other organic compounds in dead organisms and waste products into simpler compounds, including ammonium (NH4+). This process, called mineralization, is essential for recycling nitrogen within ecosystems, making it available for use by plants again.
11.
Which process in the carbon cycle involves the conversion of organic carbon to carbon dioxide?
Correct Answer
B. Respiration
Explanation
Respiration is a biochemical process in which organic carbon (in the form of glucose) is converted back into carbon dioxide (CO2) and water (H2O), releasing energy for cellular activities. This process is fundamental for life and balances photosynthesis in the carbon cycle, as it returns CO2 to the atmosphere and oceans, making it available for photosynthesis again.
12.
The sulfur cycle is unique due to its inclusion of which atmospheric phenomenon?
Correct Answer
C. Acid rain
Explanation
The sulfur cycle includes acid rain as a unique atmospheric phenomenon, resulting from the oxidation of sulfur dioxide (SO2) and sulfur trioxide (SO3) in the atmosphere, which forms sulfuric acid upon mixing with water vapor. This acid can fall as acid rain, affecting soil and water pH levels, damaging ecosystems, and altering the availability of nutrients for plants.
13.
What is the significant impact of phosphorus runoff into aquatic ecosystems?
Correct Answer
A. EutropHication
Explanation
Phosphorus runoff leads to eutrophication, an over-enrichment of water bodies with nutrients (primarily phosphorus and nitrogen), causing excessive growth of algae. When the algae die, their decomposition consumes oxygen, leading to hypoxic conditions that can kill fish and other aquatic life, disrupting ecosystems and reducing biodiversity.
14.
Which geochemical cycle does not have a significant gaseous phase?
Correct Answer
C. pHospHorus cycle
Explanation
The Phosphorus cycle lacks a significant gaseous phase, making it unique among major biogeochemical cycles. Phosphorus moves from rocks on land to soil, where it is taken up by plants, moves through the food web, and eventually returns to the soil or sediments in water bodies, often without volatilizing into the atmosphere.
15.
What is the term for the process by which atmospheric nitrogen is converted into a form usable by plants?
Correct Answer
A. Nitrogen fixation
Explanation
Nitrogen fixation is the conversion of atmospheric nitrogen (N2) into ammonia (NH3) or related nitrogenous compounds that plants can directly utilize, typically carried out by symbiotic bacteria within root nodules of legumes or by free-living bacteria in soil. This process is essential for incorporating inert N2 gas from the atmosphere into biological processes, enabling the synthesis of vital organic molecules like amino acids and nucleotides.