An ecosystem is a community of living organisms interacting with their non-living environment. The variety of life within an ecosystem is called biodiversity, and it is crucial for maintaining a healthy planet. Every species, from the largest whale to the smallest bacterium, plays a role in an intricate web of connections. The loss of even one species can send ripples of change throughout this entire web, sometimes in ways we don't expect.
To understand this, scientists study 'keystone species.' A keystone species is an organism that helps define an entire ecosystem. While all species are important, a keystone species has a disproportionately large effect on its environment relative to its abundance. A classic example is the sea otter in the kelp forests of the Pacific coast. Sea otters are not numerous, but their role is critical. They are voracious predators of sea urchins, which in turn feed on kelp, a type of giant seaweed that forms dense underwater forests.
What happens when this keystone is removed? In the 20th century, sea otters were hunted nearly to extinction for their fur. Without their primary predator, the sea urchin population exploded. Hordes of urchins grazed uncontrollably on the kelp. As a result, ① the kelp forests began to disappear, turning into barren underwater landscapes. This chain reaction is known as a trophic cascade. The loss of the kelp forests didn't just affect the urchins; it eliminated the habitat for hundreds of other species, including fish, snails, and crabs that relied on the kelp for food and shelter.
The story of the sea otter is a powerful illustration of interconnectedness. It demonstrates that the health of an ecosystem depends on the presence of all its members, especially its keystone species. By studying these critical relationships, scientists can better understand how to protect our planet's fragile biodiversity. Conservation efforts that focus on protecting keystone species can have a widespread, positive impact, helping to restore the balance of an entire ecological community. Understanding ecosystems biodiversity is an important part of learning about our world. The more we explore ecosystems biodiversity, the better we understand how things work.
A. surprisingly small for its size.
B. much bigger than expected based on its small population.
C. only important for a short period of time.
D. difficult to measure or observe.
A. Simple and easy to understand
B. New and recently discovered
C. Complex and full of interconnected parts
D. Strong and unbreakable
A. Sea otters are the most important animal in the Pacific Ocean.
B. The concept of keystone species illustrates how the loss of a single species can critically damage the delicate balance of its entire ecosystem.
C. Sea urchins are a destructive species that should be removed from kelp forests.
D. Hunting sea otters for their fur was the biggest ecological disaster of the 20th century.
A. Sea otters protect sea urchins from other animals.
B. Sea otters compete with sea urchins for kelp.
C. Sea otters are the main predators of sea urchins.
D. Sea otters and sea urchins help each other find food.
A. trigger a chain of harmful effects on many other species
B. allow the ecosystem to recover more quickly without it
C. have no impact on animals that live in a different layer of the forest
D. cause scientists to create identical species in a laboratory
A. the ocean floor became a desert-like area unable to support much life.
B. the water in the ocean became clearer for other plants to grow.
C. the sea urchins ate all the kelp and then moved to a new area.
D. the kelp forests were able to regrow quickly once the urchins left.
A. decoration, making the ecosystem more interesting.
B. regulation, keeping other populations in balance.
C. isolation, living separately from other species.
D. competition, fighting with all other species for resources.
A. To persuade readers to donate to sea otter conservation funds.
B. To provide a concrete and clear illustration of the abstract concept of a 'keystone species'.
C. To prove that all ecosystems are located in the ocean.
D. To entertain the reader with an interesting story about an animal.
A. The definition of an ecosystem as a community of organisms.
B. The fact that sea otters were hunted for their fur in the 20th century.
C. The description of the trophic cascade where the loss of kelp eliminated habitat for hundreds of species.
D. The statement that conservation efforts can have a positive impact.
A. "Every species, from the largest whale to the smallest bacterium, plays a role in an intricate web of connections."
B. "A keystone species is an organism that helps define an entire ecosystem."
C. "They are voracious predators of sea urchins, which in turn feed on kelp..."
D. "...it eliminated the habitat for hundreds of other species, including fish, snails, and crabs that relied on the kelp for food and shelter."
Q1. What is a 'keystone species'?
(A) A. The most common species in an ecosystem
(B) B. A species that has a very large effect on its ecosystem relative to its numbers
(C) C. A species that eats rocks and stones
(D) D. The first species to ever live in an ecosystem
Q2. What does 'biodiversity' mean?
(A) A. The study of animal biographies
(B) B. The variety of life in an ecosystem
(C) C. The amount of water in an ecosystem
(D) D. A dangerous chemical
Q3. In one sentence, explain what a trophic cascade is, using the passage's example.
Q4. What does 'intricate' mean?
(A) very complicated or detailed.
(B) the variety of life in the world or in a particular habitat or ecosystem.
(C) a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically.
(D) wanting or devouring great quantities of food; having a very eager approach to an activity.
Self-Reflection
How did you feel about this reading?
Confident / Okay / Confused - Circle one
What is one new word you will remember?
| Problem # | My Answer | Error Type | What I Learned / Correct Answer |
|---|---|---|---|
| #2 | B | Vocabulary | "I confused 'affect' with 'effect'. Affect = verb, effect = noun." |
Error Types: Vocabulary (어휘) | Grammar (문법) | Comprehension (독해) | Inference (추론) | Careless (실수)
| # | Answer | Type | Explanation |
|---|---|---|---|
| 1 | B | marker_reference | The passage states that a keystone species has this effect 'relative to its abundance' and uses the example of sea otters, which 'are not numerous.' The prefix 'dis-' often means 'not' or 'opposite,' and 'proportionate' means balanced. Therefore, 'disproportionately large' means an effect that is not in balance with, or much larger than, its cause (the small number of animals). B correctly captures this meaning. |
| 2 | C | vocabulary | In paragraph 1, 'intricate' is used to describe a 'web of connections' where the loss of one species can cause 'ripples of change.' A web is a structure with many connected threads, suggesting complexity. The idea that change ripples in unexpected ways also points to a complicated system. Therefore, 'complex and full of interconnected parts' is the best definition. A is the opposite, while B and D are not supported by the context. |
| 3 | B | main_idea | The passage introduces the idea of biodiversity and an interconnected web, then uses the sea otter as a detailed example to explain the concept of a 'keystone species' and the 'trophic cascade' that results from its removal. Option B correctly identifies this central argument: the sea otter is an example of the larger principle. A, C, and D are all details or potential overstatements related to the example, not the main idea of the entire passage. |
| 4 | C | cause_effect | Paragraph 2 explicitly states, 'They are voracious predators of sea urchins.' This is a direct statement of the cause-and-effect relationship in the food chain where one animal eats another. C is a direct restatement of this fact. The other options describe different ecological relationships (mutualism, competition) that are not supported by the text. |
| 5 | A | inference | The passage explains that an ecosystem is a community where living organisms interact with each other and their environment. The word 'community' and 'interacting' imply interconnectedness, so removing one species would disrupt the web of relationships that other species depend on. |
| 6 | A | inference | The word 'barren' means empty, bleak, and unable to produce much life. By describing the landscape this way, the author implies a severe and destructive transformation. The passage follows this by stating the change 'eliminated the habitat for hundreds of other species.' This supports the idea that the area became a desolate, desert-like environment, as described in A. B and D are overly optimistic and contradicted by the negative tone, while C focuses only on the urchins, not the wider impact on the landscape. |
| 7 | B | character_analysis | The entire example focuses on how the sea otter's predation on sea urchins keeps the urchin population from destroying the kelp forest. By doing this, the otter maintains the health and balance of the whole system. This is a role of regulation. The text shows the otter is deeply connected, not isolated (C) or purely competitive (D). Its role is functional and critical, not decorative (A). |
| 8 | B | author_purpose | The passage first introduces the scientific term 'keystone species' and then immediately says, 'A classic example is the sea otter.' The detailed story that follows serves to make this complex, abstract idea easy to understand. The author's primary purpose is to explain the science. B accurately describes this educational strategy. While the story might be entertaining (D) or inspire conservation (A), its main function in this expository text is to explain the key concept. |
| 9 | C | evaluate | The claim is that biodiversity (variety of life) is crucial. The most powerful evidence would show what happens when that variety is lost. Option C details the severe consequences of losing the kelp: 'it eliminated the habitat for hundreds of other species.' This directly demonstrates that the loss of one part of the ecosystem (reducing biodiversity) had a massive negative impact, proving its crucial importance. A is a definition, B is a historical fact but doesn't show the impact, and D is about solutions, not the problem's severity. |
| 10 | D | text_evidence | This question asks for the best evidence of 'widespread, negative effects.' Option D explicitly states that the loss of kelp (caused by the removal of otters) 'eliminated the habitat for hundreds of other species.' This is the clearest and most direct statement of a widespread negative consequence in the entire passage. A is a general statement of the concept, B is a definition, and C describes a single link in the food chain, not the widespread result. |
| MQ1 | B | mini_quiz | A keystone species is one that has a disproportionately large impact on its environment compared to how many of them there are, like the sea otter in the kelp forest. |
| MQ2 | B | mini_quiz | Biodiversity refers to the variety of different species of plants, animals, and microorganisms in a specific habitat or in the world as a whole. |
| MQ3 | mini_quiz | A trophic cascade is a chain reaction where removing a top predator like the sea otter causes a huge increase in its prey, the sea urchins, which then destroy the kelp forest habitat. | |
| MQ4 | A | mini_quiz | 'intricate' means very complicated or detailed. |
이번 주 학습은 생태계의 섬세한 균형과 '핵심종'의 중요성에 대해 배우는 과학 정보 지문입니다. 자녀가 글을 읽은 후, '우리 동네 생태계에는 어떤 동식물이 서로 연결되어 있을까?'와 같은 질문으로 주변 환경에 대한 관심을 유도해 보세요. 글에 나온 '연쇄 효과(trophic cascade)'라는 개념은 하나의 행동이 예상치 못한 큰 결과로 이어질 수 있다는 중요한 교훈을 줍니다. 이 원리를 일상생활의 예시와 연결하여 설명해주시면 비판적 사고력 확장에 도움이 될 것입니다.
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