Ocean Acidification - TOEFL iBT® Reading Practice Test

Ocean acidification, caused by increasing levels of carbon dioxide in the atmosphere, is a pressing environmental issue with wide-reaching impacts on marine life and ecosystems. The TOEFL Reading section often features such scientific topics, requiring analysis and understanding of cause-and-effect relationships.

Practising passages on 'Ocean Acidification' equips you with the skills to interpret data, understand complex systems, and answer related questions effectively—key to excelling in the TOEFL Reading section.

Reading Instructions:

• You have 15 minutes to read the following passage and answer all 9 questions related to it.
• Most questions are worth 1 point, but the last question is worth more. The directions indicate how many points you will receive for that specific question.
• The specific section/paragraphs have been provided again with the question for ease of understanding and quick solution.
• Some questions include a word or phrase that is highlighted in the question as well as in
  the paragraph for quick reference. 

Ocean acidification is a big environmental problem that involves the ongoing drop in the pH levels of the Earth's oceans, mainly caused by the intake of carbon dioxide (CO2) from the atmosphere. Since the late 18th century, around 30% of the CO2 released into the air has been absorbed by the oceans. This process starts a series of chemical changes that form
carbonic acid, which then breaks down into baking soda and hydrogen ions. The rise in hydrogen ions leads to a lower pH. This makes seawater more acidic. This change in ocean chemistry poses serious threats to marine environments, especially to organisms like corals, mollusks, and certain plankton species, which need carbon compounds to build their
calcium carbonate structures.

The effects of ocean acidification are deep and varied, impacting not just individual species but entire environments. For example, coral reefs, which are crucial for the variety of life in the ocean and provide important services like coastal protection and habitats for many marine species, are especially at risk. The drop in carbon compounds due to acidification makes it harder for corals to create their calcium carbonate skeletons. This leads to weaker structures that are more likely to wear and get diseases. Research in places with high CO2 levels, like the Great Barrier Reef, shows worrying declines in coral cover. Some estimates suggest that up to 50% of coral reefs could be lost by 2050 if things keep going this way. Losing coral reefs can have ripple effects on marine life, as these environments are critical habitats and food sources for many species.

In addition to corals, other marine organisms also suffer from ocean acidification. Shellfish, such as oysters, clams, and some types of plankton, struggle to form their shells, which are made of calcium carbonate. Studies have found that higher CO2 levels can result in thinner shells and higher death rates among young shellfish, with some populations seeing declines of up to 70% in acidic waters. This is particularly worrying for fisheries and fish farming, as shellfish are important species that play a big role in global food security. Also, the impact of acidification reaches the wider marine food web, as many fish species
depend on shellfish as their main food source. So, the drop in shellfish populations could upset the balance of marine environments and threaten the livelihoods of communities that rely on these resources.

 The effects of ocean acidification go beyond individual species; they also affect ecological connections and behaviors. For instance, research shows that increased acidity can hurt fish's ability to sense their surroundings, making it harder for them to spot predators and food. This change in behavior can lead to lower survival rates and affect population dynamics. Also, the disturbance of predator and prey relationships can have far-reaching consequences for marine environments. As fish populations decline, the species that depend on them for food may also struggle, possibly leading to a collapse of local fisheries and changing the structure of marine communities. And the interaction between ocean acidification and other stressors, like rising sea temperatures and pollution, makes the situation even more complicated, as these factors can worsen the negative effects on marine life.

While the effects of ocean acidification are worrying, theres still a lot to learn about the long-term effects and how marine organisms might adapt. Some species may have the ability to adjust to changing conditions, but the rate of acidification is happening much faster than many organisms can evolve. For instance, certain types of plankton have shown some ability to cope with acidification, but this adaptability may not apply to all species. Understanding these connections is key to predicting the future of marine environments and creating effective conservation strategies. Additionally, looking at past geological events, like the Paleocene-Eocene Thermal Maximum, gives us valuable insights into how marine life responded to rapid changes in ocean chemistry.

In conclusion, ocean acidification is a major environmental challenge that threatens the health of marine environments and the livelihoods of communities that rely on ocean resources. As atmospheric CO2 levels keep rising, the oceans will absorb more carbon, leading to further acidification. The effects on the variety of life, fisheries, and global food security are serious and need urgent attention from scientists, policymakers, and the public. Ongoing research is crucial to understand the complex dynamics of ocean acidification and to guide strategies aimed at reducing its effects. As the world deals with climate change, addressing ocean acidification must be a priority to ensure the strength of marine ecosystems for future generations. Questions remain about how well marine species can adapt over the long term and how effective potential solutions will be, highlighting the need for continued exploration in this important area of environmental science. 

Directions: Once you have read the passage, answer the following questions.

Paragraph 1 

Ocean acidification is a big environmental problem that involves the ongoing drop in the pH levels of the Earths oceans, mainly caused by the intake of carbon dioxide (CO2) from the atmosphere. Since the late 18th century, around 30% of the CO2 released into the air has been absorbed by the oceans. This process starts a series of chemical changes that form carbonic acid, which then breaks down into baking soda and hydrogen ions. The rise in hydrogen ions leads to a lower pH. This makes seawater more acidic. This change in ocean chemistry poses serious threats to marine environments, especially to organisms like corals, mollusks, and certain plankton species, which need carbon compounds to build their calcium carbonate structures.

Factual Information Questions

1. According to paragraph 1, what is the primary cause of ocean acidification?
   
   1. The increase in ocean temperature
   2. The intake of carbon dioxide from the atmosphere
   3. The depletion of oxygen levels in the ocean
   4. The rise in sea levels

Negative Factual Information Questions

1. The author mentions all of the following as consequences of ocean acidification in
   paragraph 1 EXCEPT:
   
   1. The formation of carbonic acid
   2. The increase in hydrogen ions
   3. The rise in fish populations
   4. The threat to organisms that build calcium carbonate structures

Paragraph 2 

The effects of ocean acidification are deep and varied, impacting not just individual species but entire environments. For example, coral reefs, which are crucial for the variety of life in the ocean and provide important services like coastal protection and habitats for many marine species, are especially at risk. The drop in carbon compounds due to acidification makes it harder for corals to create their calcium carbonate skeletons. This leads to weaker structures that are more likely to wear and get diseases. Research in places with high CO2 levels, like the Great Barrier Reef, shows worrying declines in coral cover. Some estimates suggest that up to 50% of coral reefs could be lost by 2050 if things keep going this way. Losing coral reefs can have ripple effects on marine life, as these environments are critical habitats and food sources for many species.

Inference Questions

1. What can be inferred from paragraph 2 about the importance of coral reefs?
   
   1. They are not significantly affected by ocean acidification.
   2. They play a crucial role in maintaining marine biodiversity.
   3. They are primarily important for commercial fishing.
   4. They are less important than other marine environments.

Negative Factual Information Questions

1. Why does the author mention the Great Barrier Reef in paragraph 2?
   
   1. To highlight a successful conservation effort
   2. To provide an example of a location severely affected by ocean acidification
   3. To compare coral reefs with other marine environments
   4. To suggest that coral reefs are thriving despite challenges

Paragraph 3 

In addition to corals, other marine organisms also suffer from ocean acidification. Shellfish, such as oysters, clams, and some types of plankton, struggle to form their shells, which are made of calcium carbonate. Studies have found that higher CO2 levels can result in thinner shells and higher death rates among young shellfish, with some populations seeing declines of up to 70% in acidic waters. This is particularly worrying for fisheries and fish farming, as shellfish are important species that play a big role in global food security. Also, the impact of acidification reaches the wider marine food web, as many fish species depend on shellfish as their main food source. So, the drop in shellfish populations could upset the balance of marine environments and threaten the livelihoods of communities that rely on these resources.

Rhetorical Purpose Questions

1. The word upset in paragraph 3 is closest in meaning to:
   
   1. Restore
   2. Disturb
   3. Enhance
   4. Maintain

Vocabulary Questions

1. Which of the sentences below best expresses the essential information in the following
   text in paragraph 3?
   1. Higher CO2 levels lead to thinner shells and increased mortality in young shellfish.
   2. Young shellfish are unaffected by higher CO2 levels.
   3. Shellfish populations are thriving in acidic waters.
   4. Higher CO2 levels have no impact on shellfish.

Sentence Simplification Questions

1. Which of the sentences below best expresses the essential information in the following text in paragraph 3?

      "Studies have found that higher CO2 levels can result in thinner shells and higher death rates among young shellfish, with some populations seeing declines of up to 70% in acidic waters."

   1. Higher CO2 levels lead to thinner shells and increased mortality in young shellfish.
   2. Young shellfish are unaffected by higher CO2 levels.
   3. Shellfish populations are thriving in acidic waters.
   4. Higher CO2 levels have no impact on shellfish.

Paragraph 4 

The effects of ocean acidification go beyond individual species; they also affect ecological connections and behaviors. For instance, research shows that increased acidity can hurt fishs ability to sense their surroundings, making it harder for them to spot predators and food. This change in behavior can lead to lower survival rates and affect population dynamics. Also, the disturbance of predator and prey relationships can have far-reaching consequences for marine environments. As fish populations decline, the species that depend on them for food may also struggle, possibly leading to a collapse of local fisheries and changing the structure of marine communities. And the interaction between ocean acidification and other stressors, like rising sea temperatures and pollution, makes the situation even more complicated, as these factors can worsen the negative effects on marine life.

Directions: An introductory sentence for a brief summary of paragraph 4 is provided below. Complete the summary by selecting the TWO answer choices that express the most important ideas in the paragraph. Ocean acidification affects not only individual species but also

1. Ocean acidification affects not only individual species but also
   
   1. fishes' ability to sense their surroundings
   2. the overall health of marine ecosystems
   3. the economic viability of fisheries
   4. the reproductive behaviours of marine organisms

Prose Summary Questions

Paragraph 5 

The effects of ocean acidification go beyond individual species; they also affect ecological connections and behaviours. For instance, research shows that increased acidity can hurt fishs ability to sense their surroundings, making it harder for them to spot predators and food. This change in behaviour can lead to lower survival rates and affect population dynamics. Also, the disturbance of predator and prey relationships can have far-reaching consequences for marine environments. As fish populations decline, the species that depend on them for food may also struggle, possibly leading to a collapse of local fisheries and changing the structure of marine communities. And the interaction between ocean acidification and other stressors, like rising sea temperatures and pollution, makes the situation even more complicated, as these factors can worsen the negative effects on marine life.

Insert Missing Sentence Question

1. In paragraph 5, there is a missing sentence. The paragraph is repeated below and shows four letters (A, B, C, and D) that indicate where the following sentence could be added. This highlights the urgency of studying marine adaptability. Where would the sentence best fit?
   
   1. While the effects of ocean acidification are worrying, theres still a lot to learn about the
      long-term effects and how marine organisms might adapt.
   2. Some species may have the ability to adjust to changing conditions, but the rate of acidification is happening much faster than many organisms can evolve.
   3. Understanding these connections is key to predicting the future of marine environments and creating effective conservation strategies.
   4. Additionally, looking at past geological events, like the Paleocene-Eocene Thermal Maximum, gives us valuable insights into how marine life responded to rapid changes in  ocean chemistry.

Paragraph 6 

In conclusion, ocean acidification is a major environmental challenge that threatens the health of marine environments and the livelihoods of communities that rely on ocean resources. As atmospheric CO2 levels keep rising, the oceans will absorb more carbon, leading to further acidification. The effects on the variety of life, fisheries, and global food security are serious and need urgent attention from scientists, policymakers, and thepublic. Ongoing research is crucial to understand the complex dynamics of ocean acidification and to guide strategies aimed at reducing its effects. As the world deals with climate change, addressing ocean acidification must be a priority to ensure the strength of marine ecosystems for future generations. Questions remain about how well marine species can adapt over the long term and how effective potential solutions will be, highlighting the need for continued exploration in this important area of environmental science. 

Purpose of the Passage Questions

1. What is the main purpose of paragraph 6?
   
   1. To summarise the key points about ocean acidification
   2. To provide a historical context for ocean acidification
   3. To suggest potential solutions to ocean acidification
   4. To highlight the economic impact of ocean acidification

Answer Key with Explanation for TOEFL Reading Passage - Ocean Acidification

1. Answer: B
Explanation: The passage clearly states that ocean acidification is primarily caused by the intake of carbon dioxide (CO2) from the atmosphere. This is the main focus of the first paragraph, which discusses how CO2 absorption leads to a drop in pH levels in the oceans.

2. Answer: C
Explanation: The passage discusses various consequences of ocean acidification, including the formation of carbonic acid, the increase in hydrogen ions, and the threats to organisms that build calcium carbonate structures. However, it does not mention any rise in fish populations; rather, it implies that fish populations may decline due to the effects of acidification.

3. Answer: B
Explanation: The passage highlights the importance of coral reefs in providing habitats and services for marine life. It suggests that their decline could have significant ripple effects on marine biodiversity, indicating their crucial role in maintaining the overall health of marine ecosystems.

4. Answer: B
Explanation:The mention of the Great Barrier Reef serves to illustrate a specific case where ocean acidification has led to worrying declines in coral cover. This example underscores the severity of the issue and helps to contextualise the broader impacts of ocean acidification.

5. Answer: B
Explanation:In this context, "upset" means to disturb the balance or stability of marine environments. The passage discusses how the decline in shellfish populations could disrupt the marine food web, which aligns with the meaning of disturb.

6. Answer: A
Explanation:This option accurately captures the essential information from the original sentence, summarising the impact of higher CO2 levels on shellfish without losing any critical details about the consequences.

7. Answer: A
Explanation: Both options highlight significant ideas from paragraph 4. The first option addresses the direct impact of acidification on fish behaviour, while the second option encompasses the broader implications for marine ecosystems, making them key points in summarising the paragraph.

8. Answer: B
Explanation: The missing sentence fits best after this option because it emphasises the urgency of studying marine adaptability in the context of the rapid rate of acidification, reinforcing the idea that understanding adaptability is crucial.

9. Answer: A
Explanation: The main purpose of paragraph 6 is to summarise the overall findings and implications of ocean acidification discussed throughout the passage. It encapsulates the urgency and importance of addressing this environmental challenge.

10. Answer: A
Explanation: These three options reflect the main ideas presented in the passage. They highlight the causes of ocean acidification, the challenges faced by marine organisms, and the specific vulnerability of coral reefs, all of which are central themes in the text. Options D and E do not accurately represent the passage content.

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