EigoPro 1級 読解 — The Brittle Bargain: How Coral's Greatest Asset Became Its Achilles' Heel

The architecture of a coral reef testifies to one of evolution's most consequential bargains. Reef-building corals are, in themselves, unremarkable polyps incapable of producing the prodigious limestone scaffolding that underpins entire marine ecosystems. Their power derives instead from a partnership: microscopic algae called zooxanthellae take up residence within coral tissue, photosynthesising in the sunlit shallows and transferring as much as ninety percent of the resulting sugars to their host. In return, the algae receive shelter and a steady supply of nutrients. This metabolic exchange is so efficient that it permits corals to flourish in waters otherwise too nutrient-poor to sustain such exuberant life, transforming barren tropical shallows into the most biologically diverse habitats on the planet, and it is precisely this efficiency that has allowed reefs to accrete over millennia into structures visible from orbit. Yet the very intimacy that confers this advantage also encodes a profound vulnerability, a flaw written into the partnership at its inception. The symbiosis operates within a narrow thermal envelope, and when sea temperatures climb even a degree or two beyond the customary summer maximum, the algae's photosynthetic machinery malfunctions, leaking molecules toxic to the coral that hosts it. The host responds by expelling its tenants, and with them the pigments that lend reefs their characteristic colour. The resulting pallor—what we call bleaching—is not death itself but a desperate severance, a gamble that cooler waters might permit recolonisation before starvation intervenes. Increasingly, however, that reprieve never arrives, and the bleached skeleton is overgrown by suffocating weed. Herein lies the cruel arithmetic of a warming ocean. The alliance that built the reefs is the same alliance that warming dismantles, for a relationship optimised over geological time for stability cannot be renegotiated within the compressed span of anthropogenic change. To celebrate the partnership's productivity while lamenting its fragility is to misunderstand the matter: the two are inseparable. What evolution honed as an asset has, under conditions it never anticipated, been converted into a liability, and the reefs that took ages to build may unravel within a single human lifetime.

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この単元の問題を3問、解説つきで公開しています

1級 · 読解 · 全5問

問 1

Which statement best captures the central argument of the passage?

  • The coral-algae partnership is simultaneously the source of reefs' success and the mechanism of their vulnerability to warming.
  • Corals could survive warming if they evolved to host more heat-tolerant species of algae.
  • Reefs are declining mainly because warmer water carries fewer of the nutrients corals require.
  • Bleaching is a recently discovered phenomenon whose causes remain poorly understood by scientists.
Phrase

the very intimacy that confers this advantage also encodes a profound vulnerability

1級読解主旨把握論旨
⚡ひとことで

筆者の核心は 長所と弱点が不可分 であるという逆説。

選択肢の解説Choice Analysis

「The coral-algae partnership is simultaneously the source of reefs' success and the mechanism of their vulnerability to warming.」

正解

本文は「The alliance that built the reefs is the same alliance that warming dismantles」と述べ、共生がもたらす繁栄と脆弱性が表裏一体であると論じる。「the very intimacy that confers this advantage also encodes a profound vulnerability」が論旨の核。よって長所と弱点を同一の関係から導く選択肢が正解。

  • 「Corals could survive warming if they evolved to host more heat-tolerant species of algae.」

    = 耐熱性の藻類に進化すれば生き残れるという主張 ━ 本文は地質学的時間で最適化された関係は人為的変化の短期間では再交渉できないとし、適応による救済を否定している。。

  • 「Bleaching is a recently discovered phenomenon whose causes still remain poorly understood by marine scientists.」

    = 白化は最近発見され原因も不明という見方 ━ 本文は白化の機構（藻類の光合成装置の不調と毒性分子の放出）を明確に説明しており、原因不明とはしていない。。

  • 「Reefs are declining mainly because warmer water carries fewer of the nutrients corals require.」

    = 温暖化で栄養が減るため衰退するという説明 ━ 本文は栄養不足の海でも繁栄できる効率性を長所として挙げており、衰退の主因は栄養減少ではなく熱による共生崩壊だとする。。

▦Collocation
パターン意味例
confer an advantage優位性を与えるThe deep roots confer an advantage during droughts.
encode a vulnerability脆弱性を内包するMonoculture can encode a vulnerability to a single pest.
a profound vulnerability深刻な脆弱性The supply chain revealed a profound vulnerability.
the source of success成功の源泉Its candour was the source of the brand's success.
inseparable from～と不可分であるIts productivity is inseparable from its fragility.
❝例文

  • The reef's productivity and its fragility are two faces of the same bargain.

    サンゴ礁の生産性と脆弱性は同じ取引の表裏である。

  • What once conferred an advantage now encodes a fatal weakness.

    かつて優位性を与えたものが今や致命的弱点を内包する。

  • The author argues the two qualities are inseparable.

    筆者は両者が不可分だと論じる。

  • A strength optimised for one era can become a liability in another.

    ある時代に最適化された長所は別の時代では負債になりうる。

💡Tip · 覚えるコツ

主旨設問では、本文の 逆説（paradox） を正確に保持した選択肢を選ぶ。一方だけを強調する選択肢は罠。

問 2

According to the passage, what do the zooxanthellae provide to the coral?

  • Up to ninety percent of the sugars produced through their photosynthesis.
  • A protective limestone scaffolding that supports the reef.
  • The pigments that the coral uses to capture sunlight directly.
  • A steady supply of nutrients drawn from the surrounding water.
Phrase

transferring as much as ninety percent of the resulting sugars to their host

1級読解詳細把握
⚡ひとことで

藻類はサンゴに 光合成由来の糖 を供給する。

選択肢の解説Choice Analysis

「Up to ninety percent of the sugars produced through their photosynthesis.」

正解

本文は藻類が「photosynthesising in the sunlit shallows and transferring as much as ninety percent of the resulting sugars to their host」と述べる。供給するのは光合成で得た糖であり、これが正解。

  • 「A protective limestone scaffolding that supports the reef.」

    = サンゴ礁を支える石灰の骨格を提供する ━ 骨格（limestone scaffolding）はサンゴ自身が産み出すものであり、藻類が提供するものではない。。

  • 「A steady supply of nutrients drawn from the surrounding water.」

    = 周囲の水から得た栄養を安定供給する ━ 本文では栄養と住処を受け取るのは藻類の側（「the algae receive shelter and a steady supply of nutrients」）であり、方向が逆。。

  • 「The pigments that the coral uses to capture sunlight directly.」

    = 太陽光を捉えるための色素を与える ━ 色素は藻類自身に由来し白化で失われる要素であって、サンゴへ供給される対価ではない。。

▦Collocation
パターン意味例
transfer sugars to糖を～へ渡すLeaves transfer sugars to the roots for storage.
as much as ninety percent最大で九割ものAs much as ninety percent of the heat is lost.
in return for～の見返りにIn return for shelter, they share their food.
a steady supply of安定した供給のCities need a steady supply of clean water.
take up residence within～の内部に住みつくBacteria take up residence within the gut.
❝例文

  • The algae hand over the bulk of the sugars they make.

    藻類は作った糖の大半を引き渡す。

  • Photosynthesis in the shallows fuels the partnership.

    浅瀬での光合成が共生を支える。

  • The host receives carbohydrates rather than minerals.

    宿主は鉱物ではなく炭水化物を受け取る。

  • Nearly all the sugar is passed to the coral.

    糖のほぼ全てがサンゴに渡される。

💡Tip · 覚えるコツ

詳細設問は 対価の方向（誰が誰に何を渡すか） を取り違えやすい。本文の give/receive を整理して読む。

問 3

What does the passage say happens during a bleaching event?

  • The coral dies immediately once its tissue loses all colour.
  • The algae abandon the coral in search of cooler, deeper water.
  • The coral expels its algae after their photosynthesis begins leaking toxic molecules.
  • The coral absorbs additional algae to compensate for the heat stress.
Phrase

leaking molecules toxic to the coral

1級読解詳細把握
⚡ひとことで

白化は宿主が 毒性を帯びた藻類を排出 する反応。

選択肢の解説Choice Analysis

「The coral expels its algae after their photosynthesis begins leaking toxic molecules.」

正解

本文は高温で藻類の光合成装置が不調になり「leaking molecules toxic to the coral」、その結果「The host responds by expelling its tenants」と説明する。サンゴが毒性化した藻類を排出するのが白化であり、これが正解。

  • 「The coral dies immediately once its tissue loses all colour.」

    = 色を失えばサンゴは即座に死ぬ ━ 本文は「bleaching—is not death but a desperate severance」と明記し、白化＝即死を否定している。。

  • 「The algae abandon the coral in search of cooler, deeper water.」

    = 藻類が冷たい深海を求めて去る ━ 排出するのは宿主のサンゴ側（expelling its tenants）であり、藻類が主体的に逃げるとは書かれていない。。

  • 「The coral absorbs additional algae in order to compensate for the heat stress.」

    = 熱ストレスを補うため藻類を取り込む ━ 本文では追加吸収ではなく排出（severance）が起こるとされ、説明が逆。。

▦Collocation
パターン意味例
expel its tenants間借り人を追い出すThe reef will expel its tenants under heat stress.
respond by V-ing～することで応じるThe body responds by raising its temperature.
toxic to～に有害なThe runoff proved toxic to fish.
lose its colour色を失うThe fabric loses its colour in sunlight.
a desperate severance死に物狂いの切断Selling the asset was a desperate severance.
❝例文

  • Heat makes the algae's chemistry turn poisonous.

    熱が藻類の化学反応を毒性に変える。

  • The coral ejects the partners it can no longer tolerate.

    サンゴはもはや耐えられない相手を排出する。

  • Bleaching strips away colour without causing instant death.

    白化は色を奪うが即死は招かない。

  • The pale skeleton may yet be recolonised.

    白化した骨格は再び住みつかれる可能性がある。

💡Tip · 覚えるコツ

detail で 行為の主体 が問われやすい。expel（追い出す）の主語が宿主であることを確認する。

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