雅思阅读真题（Part 2）

Seeing in the sea

海洋动物视觉适应与石首鱼研究

本篇也叫：石首鱼视觉、海洋动物视力、鱼类视觉适应、石首鱼科、鼓鱼和鸣鱼、水下视觉

Part 2 · 最近考试：2026.9.10苏州大学

本篇为雅思阅读真题（Part 2）《Seeing in the sea》，共 11 题，2026.9.10苏州大学雅思考试真题回忆，页面提供完整原文、题目、答案与解析，并支持在线机考模式免费练习。本页同时提供 Markdown 版本 供 AI 助手与搜索引擎直接读取。

文章大意

文章探讨水生动物视觉的复杂性，以美国切萨皮克湾五种石首鱼科鱼类（弱鱼、斑点海鳟、红鼓鱼、大西洋鸣鱼、斑点鱼）为对象，研究它们在不同光照和水质条件下的视觉适应，通过视网膜电图测量其对光强度的敏感度，揭示自然选择如何塑造物种视觉系统。

题目原文

A 

For animals living in water, seeing clearly is far more complicated than it is for creatures on land. A single coastal region may contain bright surface water, shadowy depths and estuaries so muddy that very little light penetrates them. The amount of available light can change dramatically with depth, weather, tides and the concentration of suspended material in the water. Its colour also varies: blue wavelengths travel furthest through clear ocean water, whereas coastal and estuarine environments tend to transmit greener, yellowish or reddish light. No visual system can perform perfectly in all these conditions. An eye designed to gather as much light as possible may function well in darkness but usually processes detail more slowly. Conversely, an eye that detects rapid movement accurately often requires stronger illumination. Aquatic animals must therefore make compromises between sensitivity, speed and sharpness. Natural selection tends to favour the combination most appropriate for the habitat and behaviour of each species.

 

B 

To investigate such adaptations, marine biologist Andrij Horodysky and an international team studied five members of the fish family Sciaenidae found in and around Chesapeake Bay in the eastern United States. These fish, commonly known as drums and croakers, are closely related, yet they occupy noticeably different ecological niches. The species selected were weakfish, spotted seatrout, red drum, Atlantic croaker and spot. Some pursue prey in open or relatively shallow water, while others search for food on or close to the seabed. Their habitats differ greatly in brightness and water clarity, making them particularly useful for studying how visual systems become specialised. The researchers expected that the eyes of each species would reflect the light conditions in which it normally fed and avoided predators.

 

C 

The scientists measured the fishes’ vision using electroretinography. This technique records small changes in electrical activity in the retina when the eye is exposed to light. Six individuals from most of the species were examined. Before testing began, each fish was kept in darkness for at least 30 minutes so that its visual system could adjust to low-light conditions. The team then conducted three main experiments. First, they varied the intensity of white light to establish how little illumination each fish could detect and how wide a range of brightness its eyes could process. Second, they presented rapidly flickering light. By gradually increasing the flicker rate, they could identify the point at which the fish’s visual system was no longer able to distinguish separate flashes. This measurement provided an indication of how quickly visual information could be processed. Finally, the researchers exposed the fish to different wavelengths to determine which colours produced the strongest retinal responses.

 

D 

The results broadly supported the idea that lifestyle shapes visual performance. Atlantic croaker and spot, which commonly feed near the bottom, displayed particularly high sensitivity to faint light. Their visual systems also operated effectively across a relatively broad range of light intensities. This would be useful in habitats where clouds of sediment, changing tides and uneven depths cause illumination to fluctuate. However, these bottom-feeding species did not dominate every aspect of vision. Their eyes appeared to be general-purpose systems, balancing sensitivity, speed and resolution rather than being exceptional at one particular task. This represents a practical evolutionary solution: an animal feeding in unpredictable conditions may benefit more from reasonable performance across several functions than from outstanding performance in only one.

 

E 

The most striking contrast occurred between weakfish and spotted seatrout. Although the two species belong to the same genus, their visual systems process changing images at very different speeds. Under strong illumination, spotted seatrout produced the fastest response to flickering light of all five species. This suits a predator that pursues moving prey in comparatively bright, shallow environments. Weakfish, by contrast, had the slowest response. At first sight, slow visual processing might seem disadvantageous. Yet by collecting light over a slightly longer period, the weakfish eye can capture more photons before transmitting a signal. This improves sensitivity in dim or turbid water, although it reduces the animal’s ability to distinguish extremely rapid movement. Its visual system has consequently exchanged speed and fine detail for better performance when light is scarce.

 

F 

The colour experiments revealed another unusual feature of weakfish vision. Most of the species responded primarily to wavelengths within the visible range from approximately violet to orange-red. Weakfish, however, also reacted to ultraviolet light. Examination of the tissues inside their eyes showed that ultraviolet wavelengths could pass through the cornea, internal fluid and lens, making some form of ultraviolet vision possible. This ability may help weakfish detect objects or prey under suitable conditions, although its usefulness is probably reduced in highly turbid water because ultraviolet light is absorbed and scattered quickly. The researchers also observed that the spectral sensitivity of weakfish and Atlantic croaker shifted towards shorter wavelengths at night. Red drum and spot showed no comparable day-to-night change. These differences demonstrate that even related species do not necessarily solve the problem of underwater vision in the same way.

 

G 
The findings suggest that the five fishes are well matched to the visual environments in which they evolved. Nevertheless, the researchers warned that those environments are being altered rapidly. Industrial development, population growth and nutrient pollution have increased the amount of organic material and suspended particles entering many estuaries. As a result, water may become darker and more turbid, changing both the quantity and the colour of the available light. Evolutionary adjustment occurs over many generations, whereas human-driven changes in water quality can happen within decades. A species whose eyes were once suitable for its habitat may therefore find it increasingly difficult to locate prey, recognise potential mates or avoid predators. Horodysky argues that studying the relationship between sensory physiology and animal behaviour is consequently important for fisheries management. Protecting a population requires more than counting the number of fish; it also requires an understanding of whether those animals can still perceive and function effectively in their changing environment.

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题目与答案

  1. An explanation of why improving one aspect of underwater vision may weaken another
    • A
    • B
    • C
    • D
    • E
    • F

    答案：A

    原文定位：An eye designed to gather as much light as possible may function well in darkness but usually processes detail more slowly. Conversely, an eye that detects rapid movement accurately often requires stronger illumination

    同义替换：「improving one aspect of underwater vision」↔「gather as much light as possible」

  2. A description of how the researchers prepared the animals before conducting the experiments
    • A
    • B
    • C
    • D
    • E
    • F

    答案：C

    原文定位：Before testing began, each fish was kept in darkness for at least 30 minutes so that its visual system could adjust to low;light conditions

    同义替换：「prepared the animals」↔「each fish was kept in darkness」，「before conducting the experiments」↔「Before testing began」，「researchers」↔「team」

  3. An example of two closely related fish displaying very different capacities for processing movement
    • A
    • B
    • C
    • D
    • E
    • F

    答案：E

    原文定位：The most striking contrast occurred between weakfish and spotted seatrout. Although the two species belong to the same genus, their visual systems process changing images at very different speeds

    同义替换：「two closely related fish」↔「two species belong to the same genus」，「displaying very different capacities」↔「at very different speeds」

  4. A visual ability whose value may decline in water containing a large amount of suspended material
    • A
    • B
    • C
    • D
    • E
    • F

    答案：F

    原文定位：This ability may help weakfish detect objects or prey under suitable conditions, although its usefulness is probably reduced in highly turbid water because ultraviolet light is absorbed and scattered quickly

    同义替换：「whose value may decline」↔「its usefulness is probably reduced」，「water containing a large amount of suspended material」↔「highly turbid water」

  5. The argument that information about animal senses has a practical role in protecting fish populations
    • A
    • B
    • C
    • D
    • E
    • F

    答案：G

    原文定位：Horodysky argues that studying the relationship between sensory physiology and animal behaviour is consequently important for fisheries management. Protecting a population requires more than counting the number of fish; it also requires an understanding of whether those animals can still perceive and function effectively in their changing environment

    同义替换：「information about animal senses」↔「studying the relationship between **sensory physiology** and animal behaviour」，「has a practical role」↔「is consequently important for fisheries management」

  6. 19-20 Which TWO characteristics did the researchers associate with the bottom-feeding Atlantic croaker and spot?
    • They were particularly effective at detecting weak light.
    • They could function across a comparatively wide range of brightness.
    • They processed flickering images faster than all the other species.
    • They were the only fish able to respond to ultraviolet wavelengths.
    • Their eyes were highly specialised for one visual task.

    答案：They were particularly effective at detecting weak light.,They could function across a comparatively wide range of brightness.

    原文定位：Atlantic croaker and spot, which commonly feed near the bottom, displayed particularly high sensitivity to faint light. Their visual systems also operated effectively across a relatively broad range of light intensities

    同义替换：「characteristics」↔「Their visual systems also operated」

  7. 21-22 Which TWO statements are correct about the weakfish?
    • It recorded the highest flicker-processing rate in bright conditions.
    • It normally depends on clear surface water when hunting.
    • Its visual responses were slower than those of the other species.
    • Its eyes allowed ultraviolet wavelengths to reach the retina.
    • Its sensitivity to different wavelengths remained unchanged between day and night.

    答案：Its visual responses were slower than those of the other species.,Its eyes allowed ultraviolet wavelengths to reach the retina.

    原文定位：Weakfish, by contrast, had the slowest response;Examination of the tissues inside their eyes showed that ultraviolet wavelengths could pass through the cornea, internal fluid and lens, making some form of ultraviolet vision possible

    同义替换：「had the slowest response」↔「visual responses were slower than those of the other species」，「allowed ultraviolet wavelengths to reach the retina」↔「internal fluid and lens」

  8. The Investigation
    The researchers used electroretinography to record electrical activity in the fishes’ 23_____ .

    答案：retina

    原文定位：This technique records small changes in electrical activity in the retina when the eye is exposed to light

    同义替换：「electroretinography」↔「technique」，「record electrical activity」↔「records small changes in electrical activity」

  9. Before being tested, the animals spent a minimum of 30 minutes in darkness. The scientists assessed the speed of visual processing by exposing each fish to 24_____ light.

    答案：flickering

    原文定位：Second, they presented rapidly flickering light. By gradually increasing the flicker rate, they could identify the point at which the fish’s visual system was no longer able to distinguish separate flashes. This measurement provided an indication of how quickly visual information could be processed

    同义替换：「assessed the speed of visual processing」↔「provided an indication of how quickly visual information could be processed」

  10. They found that species which frequently searched for food near the seabed generally had a greater 25_____ to low levels of illumination.

    答案：sensitivity

    原文定位：Atlantic croaker and spot, which commonly feed near the bottom, displayed particularly high sensitivity to faint light

    同义替换：「searched for food near the seabed」↔「feed near the bottom」，「greater」↔「high」，「low levels of illumination」↔「faint light」

  11. Although the fishes appeared well suited to their natural habitats, increasing 26_____ caused by human activity may transform their visual environment more quickly than they can evolve.

    答案：turbidity

    原文定位：As a result, water may become darker and more turbid, changing both the quantity and the colour of the available light. Evolutionary adjustment occurs over many generations, whereas human;driven changes in water quality can happen within decades

    同义替换：「increasing」↔「more」，「caused by human activity」↔「human‑driven changes in water quality」，「transform their visual environment」↔「changing both the quantity and the colour of the available light」，「more quickly than they can evolve」↔「Evolutionary adjustment occurs over many generations」

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