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AP® Environmental Science Online Course

Master the Concepts. Score a 5.
Prepare for APES with UWorld’s all-in-one learning experience featuring expert video instruction, AP-style practice, complete print and digital study resources, and personalized tools designed to help you master advanced concepts and perform at your highest level in class and on exam day.
AP Environmental Science prep course suite by UWorld
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College Board CED Aligned
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APES Practice Questions
The UWorld Advantage

Everything You Need to Master APES

Build a strong foundation for class with our illustrated APES study guide and engaging video lessons. Practice with thousands of AP-style questions and visual answer explanations that simplify complex topics.
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Engaging Video Lessons

Expert-Led AP Environmental Science Review for Every Unit

Our quick videos make tough science topics simple and interesting. Whether you like reading or watching, our AP Environmental course covers every key concept to help you succeed in class and on the exam.

UWorld’s APES Video Lessons and Online Study Guide
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Interactive Study Guides

Complete Print & Digital Study Guides for APES

Our APES print and digital prep books make it easy to review every unit and topic without relying on huge textbooks. Built-in knowledge checks help you identify strengths, focus on gaps, and study more efficiently at your pace.

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Practice

Detailed Practice Questions

with Visual, Step-by-Step Explanations

Our APES course contains comprehensive MCQ questions to help you master every topic. Illustrated explanations make it easy to understand advanced scientific principles, so you’re fully prepared for the AP exam.

Powerful APES Learning Tools

Improve Your APES Score With Smarter Study Tools

UWorld’s AP Environmental Science course helps you strengthen your understanding of core concepts, improve problem-solving skills, and stay on track throughout the school year and exam season.

Personalized Study Planner

Build a smarter AP Environmental Science review routine with UWorld’s Study Planner. Personalized insights and progress tracking help you stay organized, target weak areas, and study more effectively.

  • Create customized assessments for challenging APES topics
  • Identify and improve weaker units with performance-based insights
  • Schedule flexible review sessions that fit your routine
  • Strengthen understanding with guided explanations and visuals
  • Track progress over time with detailed performance analytics

I love the personalized schedule it makes you depending on how much time you have!”

Karina C.

UWorld’s Study Planner for AP Environment Science

Smart Flashcards

Strengthen your AP Environmental Science knowledge with smart flashcards designed for efficient review. Master essential concepts faster and retain more with every study session.

  • Reinforce important APES vocabulary, formulas, and core concepts
  • Review topics in ecosystems, population dynamics, and more.
  • Strengthen memory with active retrieval and spaced-review techniques
  • Access your flashcards anytime with a mobile-friendly study experience

My favorite thing is the flashcards. It’s a really easy and quick way to memorize key concepts.”

A.J.

UWorld’s smart, customizable flashcards for APES exam prep

Detailed Performance Analytics

Make every AP Environmental Science study session count with powerful analytics that reveal your strengths, pinpoint areas for improvement, and help you focus on the topics that will have the greatest impact on your score.

  • Analyze performance by unit, topic, and question type
  • Identify weak areas faster with targeted insights
  • Monitor progress across practice tests and review sessions
  • Track accuracy trends and overall improvement over time
  • Use performance data to guide future study sessions

I could focus on my weak areas, track my progress, and practice consistently, which made studying much more organized and effective.”

Avnita P.

UWorld APES performance dashboard

Access Anywhere

Access AP Environmental Science questions, flashcards, study guides, explanations, and analytics wherever you study. UWorld’s mobile-friendly platform helps you stay consistent and make progress at home or on the go.

  • Review AP Environmental Science concepts anytime, anywhere
  • Complete practice tests and assessments from any device
  • Access visuals and step-by-step explanations on the go
  • Sync progress seamlessly across all devices

It was easy to do, and I often found myself using it in the go and when I was free.”

Neeraj K.

Student Success Stories

Hear From Our APES Students

UWorld’s service is pretty good and helps provide a lot of explanations on subjects I haven’t been confident on before.
Bence P.
The questions here are the most realistic to the AP tests I've seen so far! I appreciate the ability to customize tests as well.
Kaila H.
The best part is that all options are well-explained, telling clearly why they are not the right option.
Syeda Huma Z.

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  • Focused APES Videos
    Expert instructors break down challenging concepts across all 9 units using clear visuals and step-by-step explanations that build understanding and confidence.
  • Print & Digital Study Guide
    Comprehensive AP Environmental Science study guides in print and digital formats help students review key concepts, environmental processes, and scientific reasoning skills through organized lessons and visual explanations.
  • 550+ Exam-Style Practice Questions
    Practice with real exam-like AP Environmental Science questions that closely mirror the timing, structure, and difficulty of the official exam, with detailed answer explanations and visual breakdowns for every question.
  • Customizable APES Quiz Generator
    Create personalized quizzes by unit, topic, or difficulty level, with options for timed practice, targeted drills, and focused review to strengthen weak areas.
  • Personalized APES Study Planner
    Build a customized APES study schedule based on your goals, availability, and exam date. Stay organized with a structured plan that keeps your prep consistent and manageable.
  • Real exam-like Timed Test Simulation
    Experience AP Environmental Science mock exams that replicate real test-day pacing, structure, and pressure to build confidence and readiness.
  • Colorful Visual Explanations
    Learn faster with colorful visuals and step-by-step answer explanations that simplify difficult concepts and clearly explain both correct and incorrect answer choices.
  • Progress Dashboard
    Monitor quiz and practice test performance with detailed analytics that track strengths, weaknesses, pacing, accuracy, and overall readiness for exam day.
  • Smart Flashcards
    Reinforce key vocabulary, environmental processes, and core concepts with interactive flashcards designed for fast, effective review on any device.
  • Digital Notebook & Study Tools
    Save explanations, bookmark important concepts, and organize personalized study notes for easier review and long-term retention throughout your AP Environmental Science prep journey.
Not Every Course Will Get You to a 5

Why UWorld Is the Better Choice for APES Prep

UWorld's AP Environmental Science course combines expert-led instruction, targeted practice, and data-driven insights to help students master challenging concepts and achieve their score goals.
Feature UWorld Other Providers
Expert-Led Video Lessons
Short, topic-specific videos for every APES concept. Long sessions covering broad topics without focus.
Complete Study Guides
Print and digital guides with built-in knowledge checks. Static guides with no reinforcement or self-testing.
Exam-Style Practice Questions
550+ exam-style questions modeled after APES. Fewer questions with lower exam accuracy.
Visual, Step-by-Step Content
High-quality visuals for Environmental Science concepts. Text-focused explanations with limited visuals.
Step-by-Step Answer Explanations
Visual step-by-step breakdowns that teach the concept. Answer revealed with no explanation of why.
Build-Your-Own Quizzes
Build targeted quizzes by unit, topic, or difficulty. Fixed practice sets with no customization options.
Real exam-like Test Simulations
Full-length tests mirroring exam-like conditions. Basic or no timed simulation available.
Personalized Study Planner
Personalized schedule for your target score & timeline. Generic plans with no score-based customization.
Performance Analytics
Dashboard highlights weak areas by unit and topic. Basic score summaries with no actionable insights.
Built-In Flashcard System
Built-in smart flashcards are available on any device. Not included. Requires separate third-party tools.
Expert-Led Video Lessons
UWorld

Short, topic-specific videos for every APES concept.

Other Providers

Long sessions covering broad topics without focus.

Complete Study Guides
UWorld

Print and digital guides with built-in knowledge checks.

Other Providers

Static guides with no reinforcement or self-testing.

Exam-Style Practice Questions
UWorld

550+ exam-style questions modeled after APES.

Other Providers

Fewer questions with lower exam accuracy.

Visual, Step-by-Step Content
UWorld

High-Quality Visuals for Environmental Science Concepts.

Other Providers

Text-Focused Explanations with Limited Visuals.

Step-by-Step Answer Explanations
UWorld

Visual step-by-step breakdowns that teach the concept.

Other Providers

Answer revealed with no explanation of why.

Build-Your-Own Quizzes
UWorld

Build targeted quizzes by unit, topic, or difficulty.

Other Providers

Fixed practice sets with no customization options.

Real exam-like Test Simulations
UWorld

Full-length tests mirroring exam-like conditions.

Other Providers

Basic or no timed simulation available.

Personalized Study Planner
UWorld

Personalized schedule for your target score and timeline.

Other Providers

Generic plans with no score-based customization.

Performance Analytics
UWorld

Dashboard highlights weak areas by unit and topic.

Other Providers

Basic score summaries with no actionable insights.

Built-In Flashcard System
UWorld

Built-in smart flashcards are available on any device.

Other Providers

Not included. Requires separate third-party tools.

Common APES Questions

AP Environmental Science Online Course: FAQs

UWorld’s AP Environmental Science course combines expert-led video lessons, illustrated study guides, and 550+ exam-style practice questions into one integrated learning system built around the College Board’s AP Environmental Science curriculum framework. Many APES resources treat content review and practice as separate activities, leaving students to connect concepts across ecosystems, biodiversity, energy resources, pollution, and global change on their own. UWorld eliminates that gap. Every component is created by subject-matter experts, regularly updated to reflect the current AP Environmental Science exam, and designed so each part reinforces the next.

What sets UWorld apart is what happens after a missed question. Rather than simply revealing the correct answer, detailed visual explanations break down the environmental concepts, scientific reasoning, and data analysis behind every question. Students learn not only why an answer is correct, but also why other options are incorrect. Combined with a personalized study planner, customizable quizzes, real exam-like timed test simulations, interactive flashcards, and a performance dashboard that tracks progress by unit and topic, students can study more efficiently and make measurable progress toward their target score. 

How UWorld compares:

UWorld vs. Kaplan: Kaplan’s AP Environmental Science resources often separate instruction from practice, and explanations may not fully explore the reasoning behind incorrect answers. UWorld connects learning, practice, and visual feedback in one seamless experience.

UWorld vs. The Princeton Review: Princeton Review focuses heavily on test-taking strategies and content summaries. UWorld emphasizes deeper understanding through detailed explanations, targeted practice, and personalized analytics that help students identify and improve weak areas.

UWorld vs. Khan Academy: Khan Academy offers broad environmental science content but is not specifically designed around the AP Environmental Science exam. UWorld provides AP-aligned practice questions, real exam-like test simulations, and a structured learning path tailored to the course framework.

UWorld vs. AP Classroom: AP Classroom provides official practice materials but lacks comprehensive instruction, personalized study planning, and detailed performance analytics. UWorld complements practice with expert teaching, visual explanations, and actionable insights that guide students throughout their preparation.

All content in the AP Environmental Science (APES) course from UWorld aligns with the latest College Board® Course and Exam Description (CED). The UWorld APES full review course includes detailed lessons, a study guide, and exam-style practice questions that cover every unit:

  • Unit 1: The Living World: Ecosystems – Explore energy flow, trophic levels, and biogeochemical cycles.
  • Unit 2: The Living World: Biodiversity – Learn about species interactions, natural disruptions, and conservation.
  • Unit 3: Populations – Examine population dynamics, growth models, and carrying capacity.
  • Unit 4: Earth Systems and Resources – Study soil formation, geology, and atmospheric processes.
  • Unit 5: Land and Water Use – Understand agriculture, deforestation, mining, and urban development.
  • Unit 6: Energy Resources and Consumption – Analyze fossil fuels, renewable energy, and energy efficiency.
  • Unit 7: Atmospheric Pollution – Investigate air quality, photochemical smog, and ozone depletion.
  • Unit 8: Aquatic and Terrestrial Pollution – Evaluate water pollution, waste management, and toxicology.
  • Unit 9: Global Change – Explore climate change, greenhouse gases, and sustainability solutions.

Each topic in the APES online course connects concepts across units to strengthen ecological reasoning and prepare students to confidently tackle both multiple-choice and free-response sections.

UWorld’s AP Environmental Science (APES) course offers a structured, exam-focused approach that free sites cannot match. Every unit is built to mirror the actual AP exam structure and difficulty, combining high-quality practice questions, vivid visuals, and concise explanations that clarify complex processes such as nutrient cycles or climate dynamics. Students can track their progress with performance analytics, create personalized quizzes, and take timed practice tests that simulate real exam conditions. 

The cohesive design ensures nothing important is missed, giving learners a clear path to earning top scores and walking into the APES exam with confidence.

The UWorld AP Environmental Science (APES) online course can be started anytime, whether during the summer, throughout the school year, or closer to exam season.

  • Summer Prep: Begin early to build a strong foundation before classes start.
  • During the School Year: Use it alongside your APES class for reinforcement and test prep.
  • Full Review Course: Ideal if your school doesn’t offer AP Environmental Science; it covers every topic from ecosystems to global change.
  • Crash Course Review: Perfect for quick, targeted review before midterms or the AP exam.

Our watch–read–practice method allows students to learn at their own pace while gaining confidence for test day.

When evaluating AP Environmental Science (APES) review courses, you should look for materials that provide:

  • Up-to-date content fully aligned with the latest College Board standards
  • Exam-style questions that mirror the real APES test format
  • Thorough answer explanations that teach reasoning, not just results
  • Progress tracking tools for identifying strengths and weaknesses
  • Interactive learning options to keep students engaged

UWorld’s full AP Environmental Science review course includes all of these features and more, offering students the structure, confidence, and quality practice needed to perform at their best on exam day.

Online learning tools like UWorld’s AP Environmental Science (APES) course make complex topics easier to grasp through interactive visuals, step-by-step solutions, and instant feedback. Students can explore environmental systems, pollution, and sustainability through engaging explanations and real-world examples that clarify difficult ideas. Each practice question is paired with detailed reasoning for every answer choice, reinforcing understanding and retention. The digital platform encourages active learning and helps students build exam confidence through consistent practice. 

UWorld doesn’t just help you review, it helps you truly master APES concepts and feel fully prepared on test day.

Tracking progress is key to improving performance, and the UWorld AP Environmental Science online course makes it simple and personalized. Students can view detailed analytics that highlight strengths, pinpoint weaknesses, and measure performance across every unit, from ecosystems and biodiversity to pollution and energy use. Interactive reports and check-for-understanding questions provide real-time feedback and progress tracking. 

The built-in performance dashboard identifies areas for targeted review, helping students spend their study time more effectively. Over time, learners can see measurable growth, build stronger study habits, and gain the confidence needed to reach their APES goals.

Our AP Environmental Science full review course offers everything students need to learn efficiently, retain key ideas, and prepare with confidence:

  • Expert-led Video Lessons: Clarify difficult concepts with visual, step-by-step explanations covering complex topics like the carbon cycle or energy flow.
  • Print & Online Study Guide: A vibrant, easy-to-navigate guide available in both print and online formats with check-for-understanding questions to reinforce learning.
  • AP-Level Practice Questions (QBank): Exam-style questions mirror the format and difficulty of the real APES exam.
  • Real exam-like FRQ Practice with Scoring: Practice free-response questions using the same format and scoring criteria as the APES exam.
  • Score-Predicting AP Environmental Science Mock Exam: Simulate real test conditions and receive a projected AP score.
  • Customizable Quiz Generator: Focus practice on specific units or topics to target your weaker areas.
  • Smart Study Planner: Create a personalized study schedule that fits your calendar and learning goals.
  • Real exam-like Timed Exams: Build endurance with practice tests that simulate real exam conditions.
  • Performance Dashboard & Smart Flashcards: Track improvement over time and retain key terms with adaptive flashcards.
Every tool works together to help students achieve top results. You can explore these features risk-free through our Free 7-Day Trial.

Yes! The UWorld AP Environmental Science review course supports every learner, from those just starting out to students aiming for a 5.

  • If you’re struggling: Clear explanations, visuals, and digital flashcards make tough topics like biogeochemical cycles or air pollution easier to master.
  • If you’re an average student: The structured watch–read–practice format helps reinforce classroom learning, close knowledge gaps, and steadily raise test scores.
  • If you’re advanced: Use our rigorous question sets, exam-style simulations, and analytics tools to fine-tune timing and boost accuracy.

No matter your level, UWorld meets you where you are and gives you the resources to improve, stay motivated, and reach your potential on the APES exam.

Absolutely. The UWorld AP Environmental Science (APES) review course breaks down challenging topics, such as energy consumption, deforestation, and air or water pollution, into clear, visual lessons and practice questions. Each explanation includes detailed reasoning and examples that connect scientific theory to real-world applications. Students can create personalized quizzes to focus on areas they find difficult and use flashcards to reinforce essential vocabulary and formulas. 

The combination of visuals, feedback, and interactive tools helps transform confusing material into lasting understanding.

Most students see meaningful improvement within 4 – 8 weeks of consistent study using the AP Environmental Science online course. Learners who use the course for a semester often experience even greater score gains thanks to steady reinforcement and progress tracking. 

Those starting late can still use it effectively as a 2 – 3 week APES crash course for focused, high-yield review before exam day. The flexible study planner helps you organize study time around your schedule and academic goals. Whether you have months or weeks, UWorld ensures every session counts toward measurable progress and confidence growth.

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Question

Researchers studying the nesting behaviors of sparrows observed that cowbirds frequently deposited their eggs into sparrow nests. Surveys showed that sparrows raising cowbird chicks alongside sparrow chicks have fewer surviving offspring per breeding season than sparrows only raising sparrow chicks.

Which of the following best identifies and describes the ecological interaction between the sparrows and cowbirds?

A. Competition, because both bird species rely on limited nesting habitat
B. Commensalism, because the cowbirds benefit without affecting the sparrows
C. Mutualism, because both bird species increase reproductive success through shared parental care
D. Parasitism, because the cowbirds benefit while decreasing the sparrows' reproductive success

Explanation

Established biological communities contain many species that, over time, have learned to coexist. Although species compete for limited resources within a community, some have adapted to form a specialized ecological interaction known as symbiosis.

A symbiotic relationship can be categorized based on the type of interaction between two symbiotic species:

  • Mutualism occurs when both species benefit.
  • Commensalism occurs when one species benefits without affecting the other.
  • Parasitism occurs when one species benefits while harming the host.

A special type of parasitism is brood parasitism where a bird, such as a cowbird, lays its eggs in another bird’s nest, such as a sparrow, and relies on the sparrow bird to raise its young. The cowbird benefits, while the sparrow’s reproductive success decreases because the cowbird chicks outcompete for food and space. Therefore the scenario depicts parasitism because the cowbirds benefits while decreasing the reproductive success of the sparrows.

(Choice A) Competition involves both species competing directly for the same limited resource. This scenario focuses on one species exploiting another’s parental care, not direct competition for the nesting sites.

(Choices B and C) Because the sparrows have fewer surviving offspring per breeding season, they are being harmed and thus this scenario demonstrates parasitism, not commensalism or mutualism.

Things to remember:
A long-term, physically close interaction between two species is called symbiosis. Parasitism is a type of symbiotic relationship where one species benefits at the expense of another.

Question

The type of power plant illustrated in the diagram would be most efficient at generating electricity all year long in which of the following terrestrial biomes?

A. Tundra
B. Desert
C. Boreal forest
D. Temperate seasonal forest

Explanation

Concentrated solar power plants generate electricity by concentrating and collecting solar energy. To maximize electricity production, these power plants require large areas of uninhabited land, plenty of sunlight, and relatively few days of rain.

Because each of Earth's major terrestrial biomes has a specific climate, they are not all suited to maximize electricity production via a concentrated solar power plant. For example, some biomes receive very little sunlight for half the year, while others have warm temperatures but frequent storms.

A desert biome would be ideal because this type of biome is characterized by high temperatures, plenty of sunlight, and low rainfall throughout the year. In addition, deserts typically have minimal plant life, open spaces, and low population densities, which allow for the construction of large concentrated solar energy plants with minimal disruptions to people and ecosystems.

(Choice A) Tundra have winters that are long and dark, which would prevent the production of electricity during the winter.

(Choice C) Boreal forests, also known as taigas, have many trees and relatively few days of sunlight due to long winters. These conditions would not be the most efficient for producing electricity all year long.

(Choice D) Although temperate seasonal forests can be suited for concentrated solar farms, this would not be the most efficient biome to produce electricity all year long because it is characterized by large trees, moderate rainfall, and cold, snowy winters.

Things to remember:
Deserts are terrestrial biomes characterized by high temperatures and low rainfall, which makes them ideal locations for concentrated solar power plants.

Passage

An Ecological Overview of Denali National Park and Preserve

During the past two million years, Denali's history has been characterized by repeated advances and retreats of a massive ice sheet. Over half of the park (Alaska Range and south) was intermittently covered by an extension of the ice sheet in Canada.…

Glacial ice has retreated significantly since the Pleistocene. Today, only about 16% of the park is covered by ice or perennial snow fields. However, glaciers continue to have a cooling effect near their termini and downstream. Glacial meltwaters affect local weather conditions and reconfigure floodplains downstream.…

The local ecosystems are shaped by the physical environment (geology, glaciers, climate). Interactions among these factors and the habitat preferences of plants create the mosaic of vegetation on the landscape. For example, stunted scattered spruce in northern areas of the park grow over permafrost, while more lush vegetation is supported on permafrost-free areas.…

The major processes on the landscape vary across ecological zones. Geomorphic disturbances such as landslides, avalanches, and other mass movements predominate in the alpine region.…

The action of flowing water is another important natural disturbance process in boreal lowlands. Large braided glacial rivers such as the McKinley, Toklat, Yentna, and Chulitna are constantly reshaping the land by shifting channels, creating new floodplain deposits, and eroding old terraces with established forests….

Denali is located in the northern boreal forest biome. The landscape is predominantly forested at elevations less than 2,500 feet, with scrub vegetation and spruce woodland in the subalpine zone and low tundra in the alpine zone (above 3,500 feet).…

Despite being a wilderness park, Denali faces threats from human activity on many scales, including increased tourism and development, introduction of exotic species, increased hunting pressures, and accumulation of trace amounts of global airborne contaminants. The retreat of glaciers and changes in vegetation due to climate change are easily seen in photographs taken only decades apart. These influences and their effects are difficult to measure, but they may dramatically alter the distribution and visibility of wildlife. Park management faces an increasing challenge to protect resources in the face of climate change and other human effects.

Credit: National Park Service

Question

The author assumes that glaciers play a significant role in the Alaskan landscape because

A. released greenhouse gases create a negative feedback loop
B. geomorphic disturbances decrease in alpine regions
C. the number of downstream flooding events decreases
D. the glacial rivers alter and reconfigure the environment

Explanation

P2: Glacial meltwaters affect local weather conditions and reconfigure floodplains downstream.

P5: Large braided glacial rivers such as the McKinley, Toklat, Yentna, and Chulitna are constantly reshaping the land by shifting channels, creating new floodplain deposits, and eroding old terraces with established forests.

Locate and summarize the points in the article that discuss the significant role that glaciers play in the Alaskan landscape. According to the article, retreating glaciers create glacial:

  • rivers, which reshape the land by shifting the flow of channels (streams and rivers).
  • meltwaters, which reconfigure floodplains downstream.

Because glaciers are a major reservoir of freshwater, their melting creates runoff that leads to the formation of freshwater biomes (rivers, streams, lakes, ponds) that provide a vital source of drinking water for wildlife and humans. As such, glaciers play a significant role in the Alaskan landscape because their glacial rivers alter and reconfigure the environment.

(Choice A) The release of greenhouse gases from glaciers is not mentioned in the article and would create a positive, not a negative, feedback loop.

(Choice B) The change in geomorphic disturbances, such as landslides and mass movements, in the alpine regions is not mentioned in the article.

(Choice C) The melting of glaciers is likely to increase, not decrease, flooding events.

Things to remember:
The runoff from precipitation and melting snow and ice creates freshwater biomes (streams, rivers, lakes, ponds), which are a vital source of drinking water.

Passage

The diagram below shows a light-dark bottle experimental setup used to investigate the primary productivity of a marine ecosystem. The experiment was performed with two samples of ocean water containing phytoplankton taken from the same area. One sample was placed in a light (clear) glass bottle, and the other sample was placed in a dark (painted black) glass bottle. Each sample was sealed and kept at a depth of 10 meters. After 24 hours, the dissolved oxygen levels were measured in each sample.

Question

Based on the experimental setup, which process in the carbon cycle is occurring in the dark bottle?

A. Respiration by phytoplankton
B. Photosynthesis in producers
C. Primary productivity in the water sample
D. Ammonification of aquatic organisms

Explanation

The carbon cycle involves the movement of carbon through the environment. The two processes in the carbon cycle that move carbon between living organisms and their environment include:

  • photosynthesis, which involves producers consuming carbon dioxide (CO2) and water (H2O) in the presence of sunlight to produce glucose (C6H12O6) and oxygen (O2).
  • cellular respiration, which involves organisms consuming O2 and C6H12O6 to produce CO2 and H2O.

Because the dark bottle in the experimental set-up blocks sunlight from reaching the phytoplankton, the phytoplankton are only able to undergo the process of respiration.

(Choices B and C) Although the experiment could be used to determine the primary productivity in the light and dark bottles, photosynthesis and primary productivity are not occurring in the dark bottle because sunlight does not enter the bottle.

(Choice D) Ammonification—the conversion of organic nitrogen to ammonium—is a process in the nitrogen cycle, not the carbon cycle.

Things to remember:
Photosynthesis and cellular respiration are processes that cycle carbon between living organisms and their environment.

Passage

Directions: Carefully read each question before answering. For questions that require an explanation or description, elaborate with specific examples and relevant content. For questions that require calculations, provide work for full credit.

The nitrogen cycle involves various processes that move nitrogen between reservoirs. Nitrogen is moved out of the largest reservoir and into ecosystems through nitrogen fixation. The movement of nitrogen between ecosystems can be facilitated by the hydrologic cycle.

(a) Describe the movement and conversion of nitrogen-containing molecules during biotic nitrogen fixation.

(b) Describe how the hydrologic cycle facilitates the movement of nitrogen between ecosystems.

Prior to the Industrial Revolution, global nitrogen fixation contributed an estimated annual 203 teragrams (Tg) of nitrogen to terrestrial and marine ecosystems. By 2010, global nitrogen fixation contributed an estimated annual 413 Tg of nitrogen to terrestrial and marine ecosystems.

(c) Calculate the percent change in global nitrogen fixation from before the Industrial Revolution to 2010. Show your work.

(d) Describe one environmental problem associated with increased nitrogen in terrestrial or marine ecosystems.

(e) Propose a solution to minimize the effects of the environmental problem described in part (d).

Of the total global nitrogen fixation in 2010, 210 Tg of nitrogen came from anthropogenic activities. Nitrogen-fixing crops used in agriculture provided 29% of that amount, and combustion reactions (which combine O2 and N2 at high temperatures) provided 14%. The remaining anthropogenic nitrogen fixation came from the Haber-Bosch process, an industrial process that combines H2 and N2 at high temperatures in the presence of a catalyst.

(f) Calculate the total amount of nitrogen (in Tg) the Haber-Bosch process produced in 2010. Show your work.

Globally, the Haber-Bosch process produces about 150 million metric tons of ammonia per year. In addition to producing ammonia, the Haber-Bosch process produces atmospheric carbon dioxide as a byproduct. For every metric ton of ammonia the Haber-Bosch process produces, approximately 1.87 tons of carbon dioxide are emitted.

(g) Calculate the total amount of carbon dioxide the Haber-Bosch process releases each day. Show your work.

Question

(a) Describe the movement and conversion of nitrogen-containing molecules during biotic nitrogen fixation.

Explanation

Student responses are provided that received 0 or 1 point for this part. The associated reasoning for the given score is provided after each response.

(a) Describe the movement and conversion of nitrogen-containing molecules that occur during biotic nitrogen fixation.

Student examples

Example of a response that receives 1 point: Nitrogen in the atmosphere is taken in by bacteria to produce ammonium in soil.

Reasoning: This response earned a point for providing the correct reactant and product of nitrogen fixation and mentioning that "bacteria" is performing the conversion.

Example of a response that receives 0 points: Nitrogen is moved out of the largest reservoir by plants.

Reasoning: This response did not earn a point because it did not provide the product of biotic nitrogen fixation and "plants" is not specific enough to describe the types of plants that support nitrogen fixation.

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Frequently Asked Questions

New Purchase: All new subscriptions go into effect from the time they are activated and not at the time of setup/purchase. A subscription can be activated immediately or any time thereafter. If your initial purchase consists of multiple courses (Qbank, Self-Assessment exam, CCS, etc.), each can be activated individually and independently via your account on our website. This process of activating a subscription after purchase allows you the flexibility to start a subscription when you are truly ready to use it.

We recommend that all subscriptions be activated within 180 days of setup/purchase. Once a subscription is activated, it cannot be paused or suspended for any reason and will run continuously for the duration of the course material.

Renewal: A renewal is an extension of time to continue access to a current activated subscription. Because a renewal is an extension to an already active subscription, it is effective from the existing expiration date, not from the day of purchase and cannot be deferred to start at a later date/time.

Note: All of our subscriptions are based on the Eastern Time Zone (GMT/UTC -5 hours or New York Time), which may be different than your local time zone.

Any of our product offerings can be purchased from our website with payment due in full at time of purchase via a credit or debit card with American Express/Discover/MasterCard or Visa logo.

You will need to register for an account in order to purchase any of our products. Once you have registered for an account or if you already have an account:

  • Log in to your UWorld account
  • Click on the Cart icon at the top of the page and then select your desired product to see a list of available packages and their prices
  • Select the package you wish to purchase
  • Verify your profile information, address, and educational status, then click the Update button
  • Enter your Billing address and credit/debit card information, then click Review Order
  • Verify that the correct product is in your cart and click Place Order
  • A purchase receipt will automatically be sent to your registered email address

If you complete your purchase but do not receive a receipt, please contact the Customer Care Team at [email protected]

You can subscribe to any of our online courses/services using a credit or debit card with a Visa, MasterCard, Discover or American Express logo. After a successful payment, your subscription will immediately be available for activation via your account on our website or available complementary mobile applications.

You can also subscribe via personal check, money order, or demand drafts taken in U.S. dollars. These types of payments should be mailed to us and should include the name of the subscription and the duration, along with the details asked for in the registration form. We will set up your account as soon as we receive your payment and notify you via email of your access credentials. All direct-mail payments must be in U.S. dollars and made payable to:

UWORLD, LLC
P.O. Box 739478

Dallas, TX 75373-9478

We do not accept cash via mail, currencies other than U.S. dollars or payments via fax.

Individuals purchasing our CPA Review product may finance their purchase using Affirm during checkout process. Your eligibility depends on your credit score and other criteria, as per Affirm’s policies (outlined here). A soft credit check, a credit check that does not affect your credit score, will be performed by Affirm to determine your loan eligibility. You will need a US based bank account to qualify.

All refunds are evaluated on a case-by-case basis for products purchased directly from UWorld. One case has no bearing on another. Refund amounts determined by UWorld are final.

In-App Purchases: We are unable to process any refunds for purchases made via mobile application (in-app). Please contact Apple for all refund/credit requests for Apple in-app purchases.

USMLE Step 2 CS, Step 3 CCS, Subject Reviews & Self-Assessment Exams: These subscriptions are non-refundable, non-transferable, and cannot be converted into another subscription.

CPA Review: Students may request to cancel their CPA review product only within 10-days of activation of any of the materials. To qualify for a refund, no more than 10% of the course (lectures, Qbank, or a combination there-of) may have been used per exam section. All CPA Review refunds are subject to a cancellation fee of $75 (for single section purchases) or $250 (for package
purchases), plus any applicable shipping charges. No return of merchandise is necessary.

All other Qbanks: Refunds are considered for subscriptions of more than 30 days. Refund amounts are based on the number of days elapsed since the subscription start date or the number of questions used, whichever amounts to a higher deductible.

Example scenarion: An individual purchases a 180-day Qbank subscription and generates a few test blocks equal to 20% of the questions in the Qbank. After 45 days, he/she requests a refund. Because the elapsed duration is greater than the percentage of questions used, the refund amount will be based on a subscription converted to the closest duration (60 days) by deducting the applicable 60-day subscription fee from the refund. In the same scenario, if the individual had used 85% of the questions, the refund would be 15% of the subscription fee paid.

Note 1: A processing fee of 10% (minimum of $10 and maximum of $25) will be applied to all refund amounts.

Note 2: All refunds, pro-rated or otherwise, must be requested within 360 days of original purchase. Refunds for purchases made more than 360 days ago will be issued as non-refundable, non-transferable store credit.

Note 3: Subscribers must notify UWorld of their intent to obtain a refund before activating their subscription (or) during the active duration. If the reset option is used or all of the questions are used, no refund will be allowed (see “I want to reset/delete my Qbank test history (or) start all over again, is this possible?” below for further details). No refunds will be offered for expired subscriptions.

Note 4: For combination package purchases, individual subscription fees will be applied when calculating the refund. If any self-assessment Exam(s) is utilized from a package, the entire purchase is rendered non-refundable.

Note 5: Although access to Qbanks via certain mobile devices is provided as an additional feature, it is not intended to be a replacement for computer access, and no refunds or cancellations will be honored due to user inability to install and/or use the provided software on any mobile device (regardless of whether the device meets the minimum system requirements).

Please use the following steps to purchase a renewal for your subscription:

  • Log in to your account on our website
  • Click on the User Icon in the top right corner of the screen
  • Click on the Renew button corresponding to your subscription
  • Select the Renewal duration you wish to purchase
  • Verify your profile information, address, and educational status, then click the Update button
  • Enter your Billing address and credit/debit card information, then click Review Order
  • Verify that the correct package is in your cart and click Place Order

Upon a successful transaction, you will be sent a confirmation email receipt.

A renewal is an extension of time to continue accessing an active subscription, and it will not start the subscription over, provide a reset, or grant access to additional questions that were not previously accessible. Because a renewal is an extension to an already active subscription, it is effective from the existing expiration date, not from the date of purchase, and cannot be deferred in any way to start at a later date/time.

Please note that to qualify for renewal pricing, you will need to renew the course before it expires. Renewals are not offered to expired subscriptions. If you fail to secure a renewal before the expiration date, you will need to purchase a new subscription at the regular price directly from our website to regain access to the material.

Note: All times and dates displayed for subscription expiration correspond with the Eastern Time Zone (GMT/UTC -5 hours or New York Time), which may be different than your local time zone.

Note: If your initial purchase was a combination package, you will need to renew each active subscription individually. You do not need to renew a course that has not been activated.

You may request to upgrade or downgrade your subscription purchase as long as it has not been activated. If you purchase a combination package, all included subscriptions must be unused. Please be advised that current subscription pricing will apply.

If your subscription has been activated, unfortunately, we cannot upgrade it retroactively. If seeking to downgrade, please refer to our refund policy for available options.

We do not offer custom duration(s) or combination packages other than those outlined on the website. Please refer to our purchase page for currently available subscriptions (including discounted combination packages for some products).

Self-Assessment exam subscriptions are for 14 days each. Subscribers whose active subscription(s) have not expired can purchase renewals from 7 days or more at any time before their active subscription expires. Please refer to the respective course description page for renewal options.

We offer a demo on each of our product pages that contains a sample of the product interface and a few sample questions. We do not offer guest/trial accounts to test our software and view materials.

It is possible to purchase a subscription as a gift for someone else. However, the intended recipient will need to register an account on our website (or have an account registered for them, with their profile information entered accurately). If the user is present at the time of purchase, the purchase can be made from their account on our website using any credit or debit card with a Visa, MasterCard, American Express, or Discover logo.

If the user is not present, or you wish for the gift to be a surprise, please contact Support directly using the contact form to arrange payment for the gift subscription. You will need to provide the user’s registered email address so the account can be located.