IELTS Reading: Decoding “Electroreception” – Vocabulary & Answer Key

When we submerge ourselves in the ocean, our world becomes blurred and distorted. Vision is limited, and sounds are chaotic. Humans are virtually helpless without specialized equipment. So, how do marine creatures manage to navigate, hunt, and defend themselves with such ease?

The answer lies in an incredible biological phenomenon called **Electroreception**—a sixth sense that allows them to detect electrical currents. This IELTS reading passage will take us deep into this silent yet signal-rich world. Let’s join ECE in uncovering these secrets and mastering these challenging reading question types!

IELTS Reading: Electroreception & Questions

(A) Open your eyes in sea water and it is difficult to see much more than a murky, bleary green colour. Sounds, too, are garbled and difficult to comprehend. Without specialised equipment humans would be lost in these deep sea habitats, so how do fish make it seem so easy? Much of this is due to a biological phenomenon known as electroreception – the ability to perceive and act upon electrical stimuli as part of the overall senses. This ability is only found in aquatic or amphibious species because water is an efficient conductor of electricity.

(B) Electroreception comes in two variants. While all animals (including humans) generate electric signals, because they are emitted by the nervous system, some animals have the ability – known as passive electroreception – to receive and decode electric signals generated by other animals in order to sense their location.

(C) Other creatures can go further still, however. Animals with active electroreception possess bodily organs that generate special electric signals on cue. These can be used for mating signals and territorial displays as well as locating objects in the water. Active electroreceptors can differentiate between the various resistances that their electrical currents encounter. This can help them identify whether another creature is prey, predator or something that is best left alone. Active electroreception has a range of about one body length – usually just enough to give its host time to get out of the way or go in for the kill.

(D) One fascinating use of active electroreception – known as the Jamming Avoidance Response mechanism – has been observed between members of some species known as the weakly electric fish. When two such electric fish meet in the ocean using the same frequency, each fish will then shift the frequency of its discharge so that they are transmitting on different frequencies. Doing so prevents their electroreception faculties from becoming jammed.

(E) Electroreception can also play an important role in animal defences. Rays are one such example. Young ray embryos develop inside egg cases that are attached to the sea bed. The embryos keep their tails in constant motion so as to pump water and allow them to breathe… If the embryo’s electroreceptors detect the presence of a predatory fish in the vicinity, however, the embryo stops moving (and in so doing ceases transmitting electric currents) until the fish has moved on. Because marine life of various types is often travelling past, the embryo has evolved only to react to signals that are characteristic of the respiratory movements of potential predators such as sharks.

(F) Many people fear swimming in the ocean because of sharks. In some respects, this concern is well grounded – humans are poorly equipped when it comes to electroreceptive defence mechanisms. Sharks, meanwhile, hunt with extraordinary precision. They initially lock onto their prey through a keen sense of smell… As the shark reaches proximity to its prey, it tunes into electric signals that ensure a precise strike on its target…

(G) Normally, when humans are attacked it is purely by accident. Since sharks cannot detect from electroreception whether or not something will satisfy their tastes, they tend to “try before they buy”… (our sinewy muscle does not compare well with plumper, softer prey such as seals). Repeat attacks are highly likely once a human is bleeding, however; the force of the electric field is heightened by salt in the blood… In areas where shark attacks on humans are likely to occur, scientists are exploring ways to create artificial electroreceptors that would disorient the sharks and repel them from swimming beaches.

(H) There is much that we do not yet know concerning how electroreception functions… Scientists are also exploring the role electroreception plays in navigation. Some have proposed that salt water and magnetic fields from the Earth’s core may interact to form electrical currents that sharks use for migratory purposes.

Questions

Questions 1-6

Reading Passage 1 has eight paragraphs, A–H.

Which paragraph contains the following information?

Write the correct letter, A–H, in boxes 1–6 on your answer sheet.

1. How electroreception can be used to help fish reproduce.
2. A possible use for electroreception that will benefit humans.
3. The term for the capacity which enables an animal to pick up but not send out electrical signals.
4. Why only creatures that live in or near water have electroreceptive abilities.
5. How electroreception might help creatures find their way over long distances.
6. A description of how some fish can avoid disrupting each other’s electric signals.

7. Shark’s __________ alert the young ray to its presence.

8. Embryo moves its __________ in order to breathe.

9. Embryo stops sending __________ when predator close by.

Questions 10 – 13

Complete the summary below. Choose NO MORE THAN THREE words from the passage for each answer.

Write your answers in boxes 10–13 on your answer sheet.

Shark Attack

A shark is a very effective hunter. Firstly, it uses its 10.__________ to smell its target. When the shark gets close, it uses 11.__________ to guide it toward an accurate attack. Within the final few feet the shark rolls its eyes back into its head. Humans are not popular food sources for most sharks due to their 12.__________. Nevertheless, once a shark has bitten a human, a repeat attack is highly possible as salt from the blood increases the intensity of the 13.__________.

Summary of the “Electroreception” Reading

The “Electroreception” passage introduces a “sixth sense” found in aquatic species, allowing them to detect electrical signals.

• Basic Principle: This sense exists only in aquatic environments because water is an efficient conductor of electricity.
• Two Main Types:
  • Passive: Only capable of receiving and decoding electric signals from other organisms for location sensing.
  • Active: Possesses specialized organs to emit electric signals, used for communication, mating, and identifying prey or predators.
• Applications in Nature:
  • Communication: Weakly electric fish can shift frequencies to avoid “signal jamming.”
  • Defense: Ray embryos stop moving (and stop emitting electricity) when they detect the electrical signals of a shark’s respiratory movements.
  • Hunting: Sharks use their sense of smell for long-distance tracking and electroreception for precise strikes at close range.
• Human Interaction and Future Outlook: Scientists are researching artificial electroreceptors to deter sharks and protect humans. This sense may also play a role in long-distance migratory navigation.

Vocabulary Summary

1. Garbled (adj): Distorted or unclear (usually referring to sound).
2. Amphibious (adj): Living or able to live both on land and in water.
3. On cue (idiom): At the appropriate moment; in response to a signal.
4. Vicinity (noun): The area near or surrounding a particular place.
5. Olfactory organs (noun phrase): Organs related to the sense of smell.
6. Sinewy muscle (noun phrase): Lean, tough, and muscular tissue.
7. Feeding frenzy (noun phrase): A state of aggressive, competitive feeding by a group of animals.
8. Disorient (verb): To make someone or something lose their sense of direction.

Answer Key & Detailed Analysis

1. C

• Information needed: How electroreception aids fish reproduction.
• Evidence (Paragraph C): “These can be used for mating signals…”

2. G

• Information needed: A potential application benefiting humans.
• Evidence (Paragraph G): “…scientists are exploring ways to create artificial electroreceptors that would disorient the sharks and repel them from swimming beaches.”

3. B

• Information needed: The term for the ability to receive but not send signals.
• Evidence (Paragraph B): “…some animals have the ability – known as passive electroreception – to receive and decode electric signals…”

4. A

• Information needed: Why only aquatic creatures possess this ability.
• Evidence (Paragraph A): “…because water is an efficient conductor of electricity.”

5. H

• Information needed: How electroreception aids long-distance navigation.
• Evidence (Paragraph H): “…electrical currents that sharks use for migratory purposes.”

6. D

• Information needed: How fish avoid signal interference.
• Evidence (Paragraph D): “…each fish will then shift the frequency of its discharge so that they are transmitting on different frequencies.”

7. respiratory movements

• Evidence (Paragraph E): “…the embryo has evolved only to react to signals that are characteristic of the respiratory movements of potential predators such as sharks.”

8. tail

• Evidence (Paragraph E): “The embryos keep their tails in constant motion so as to pump water and allow them to breathe…”

9. electric currents

• Evidence (Paragraph E): “…the embryo stops moving (and in so doing ceases transmitting electric currents)…”

10. keen sense of smell

• Evidence (Paragraph F): “They initially lock onto their prey through a keen sense of smell…”

11. electric signals

• Evidence (Paragraph F): “…it tunes into electric signals that ensure a precise strike on its target…”

12. sinewy muscle

• Evidence (Paragraph G): “…(our sinewy muscle does not compare well with plumper, softer prey such as seals).”

13. electric field

• Evidence (Paragraph G): “…the force of the electric field is heightened by salt in the blood…”

The “Electroreception” passage demonstrates that the natural world holds wonders far beyond our ordinary perception. In terms of skills, this is an excellent exercise for “Locating Information” tasks, which require you to quickly grasp the main idea of each paragraph. Additionally, the “Diagram Labelling” and “Summary Completion” tasks test your ability to scan for specific details. We hope that through these detailed analyses from ECE, you have gained the necessary skills to conquer scientific reading passages in your IELTS exam.