VIDEO
TEXT
Electroreception
(Adapted for B1-level students from the British Council’s sample test)
Original text: https://takeielts.britishcouncil.org/take-ielts/prepare/free-ielts-english-practice-tests/reading-academic/section-1
- Without special equipment, humans would have difficulty communicating under deep sea water. They cannot see well in the murky water, and sound becomes garbled. However, fish manage very well. One important reason is a biological ability called electroreception, which allows animals to detect and respond to electrical signals in their environment. This ability exists only in aquatic or amphibious animals because water is a good conductor of electricity.
- There are two main types of electroreception. All animals produce small electrical signals through their nervous systems, but some animals can detect these signals from others. This is known as passive electroreception and helps them locate nearby animals. Some species have a more advanced system called active electroreception. These animals can produce their own electrical signals and use them to find food, communicate during mating, and mark their territory. They can also sense small differences in electrical resistance, which helps them decide whether another animal is prey, a predator, or not important. However, this ability works only over a short distance.
- A well-known example of active electroreception is the Jamming Avoidance Response. When two weakly electric fish with the same signal frequency meet, they change their signals so that they are different. This prevents confusion and allows each fish to recognize its own signals clearly. In a way, this is similar to people using different radio channels to avoid interference.
- Electroreception is also important for defence. For example, young rays develop inside egg cases on the sea floor. They move their tails to breathe, but if they detect a nearby predator, they stop moving. This stops their electrical signals and makes it harder for predators to find them. However, they do not react to every passing animal. They respond mainly to signals that match the breathing movements of predators such as sharks.
- Sharks are highly effective hunters. First, they use their strong sense of smell to locate prey. Then, as they get closer, they rely on electroreception to make a precise attack. This sense is so powerful that sharks can even attack with their eyes closed to protect them. Most shark attacks on humans happen by accident, as sharks cannot easily tell whether something is suitable food. They may bite first and then decide. However, if a person is bleeding, the electrical signals in the water become stronger, which can lead to repeated attacks.
- Scientists are now studying ways to protect humans by creating artificial electrical signals that could confuse or repel sharks. Even so, much about electroreception remains unknown. Researchers are still trying to understand how the brain processes these signals and how animals use them for navigation. Some believe that ocean water and the Earth’s magnetic field may work together to create electrical signals that help animals travel long distances. Electroreception is therefore a fascinating and important ability that plays a key role in survival in the marine world.
NEW WORDS
Murky, garble, comprehend, specialized, habitat, biological, phenomenon, electroreception, ability, perceive, stimulus, sense, aquatic, amphibious, species, efficient, conductor, variants, generate, emit, nervous, decode, creatures, possess, organ, on cue, mating, territorial, display, differentiate, resistance, current, encounter, prey, predator, range, host, fascinating, Jamming, Avoidance, Response, mechanism, frequency, each, discharge, prevent, faculty, yell, hapless, novice, cluttering, air waves, dispute, role, defense, ray fish, embryo, case, detect, vicinity, cease, move on, marine, respiratory movement, potential, shark, well grounded, lock onto, keen, devote, olfactory, tune, strike, recede, by accident, sinewy, muscle, plumper, seals, heighten, feeding frenzy, occur, explore, artificial, disorient, repel, documented, alter, observation, neurological, processes, encode, decode, navigation, magnetic fields, core, interact, migratory, purpose.
GRAMMAR
Reduced relative clauses.
Examples from the text:
- a biological ability called electroreception (= which is called…)
- a more advanced system called active electroreception
- A well-known example of active electroreception is the Jamming Avoidance Response (not reduced here, but often appears as “known as…”)
- signals generated by other animals (earlier idea, implied structure type)
- animals use them for navigation (not reduced, but similar compression pattern)
IELTS READING TEST PRACTICE
Which paragraph contains the following information?
- Unlike humans, some fish can communicate by electrical signal.
- Humans also produce electrical signals but only some animals can detect them.
- One possible method to protect humans from sharks is to create electrical signals that confuse them.
- Some animals can pick up but not send out electrical signals.
- Only creatures that live in or near water have electroreceptive abilities.
- Electroreception might help creatures find their way over long distances.
- Sharks don’t purposely attack humans.
- A description of how some fish can avoid disrupting each other’s electric signals.
- How some young animals know how to avoid detection by predators.
Answer key: 1-1,2-2,3-6,4-2,5-1,6-6,7-5,8-3,9-4
EXTERNAL VIDEO
VIDEO TRANSCRIPT.
We live in a world full of electric fields. Animals, plants — even the Earth itself — create them. But only a handful of creatures can actually sense them. Sharks, rays, and skates — a whole group of animals called elasmobranchs — can detect electricity. Maybe it’s like feeling the presence of someone hiding in a dark room, a different way of experiencing their world, an extra sense that we don’t have. And for sharks and rays, it’s an extra edge for finding their prey.
The discovery of this exceptional sense dates back three hundred years — long before the discovery of electricity — to a man named Stefano Lorenzini. Lorenzini was a doctor with a passion for anatomy, who one day found himself dissecting a ray. That’s when he noticed the strangest thing: tiny pores that dotted the ray’s skin. He drew a picture showing how each pore led to a tube full of goo, and each tube ended in a little pouch. Those little round pouches reminded him of ancient Roman flasks called ampullae, so that’s what he named them. But when it came to the function of those ampullae, Lorenzini was stumped.
Three hundred years later, we’re still figuring out exactly how electroreception works, and a big part of that is studying what creates these electrical fields in the first place. Every time a fish opens its mouth to breathe, it exposes its mucus membranes to the salty water, creating a tiny voltage that disappears every time the mouth closes. At Florida Atlantic University, scientists are able to measure this phenomenon. That repeating on–off pattern is an electric frequency carried easily through salt water — two hertz, two breaths a second.
Stingrays can tune in to that same frequency like a radio channel. Take a close look at a stingray and you can see those pores. They lead to long canals that cluster together. When an electric charge enters a pore, it travels through the highly conductive gel in the canal to the ampulla, where special cells detect the current and send a message along nerves to the brain. That’s how stingrays can spot prey hidden beneath them, even though their eyes are on top of their heads.
But the ampullae aren’t just for hunting. Pores on the ray’s back also let it know if someone is trying to sneak up on it from behind. Researchers place diodes on the floor of a tank, replicating the same electric frequency as a breathing fish. They flip the current from circle to circle, and the ray strikes at the active target.
Maybe by studying how this sense works, we can learn better ways to coexist with these ancient creatures — find new ways to keep them out of our nets and away from our surfers. Of course, none of this really explains what it’s like to feel electricity. Is it as simple as flipping a switch on and off, or as varied and subtle as smell or taste? A whole spectrum of experiences hidden to the rest of us.
NEW WORDS.
Electric field, handful, creature, sense them, shark, ray, and skate, elasmobranch, edge, prey, anatomy, found himself, dissecting, pore, dot, goo, pouch, flask, ampullae, stumped, figure out, electroreception, mucus, membranes, phenomenon, frequency, hertz, tune, channel, canal, cluster, gel, cell, spot, sneak up on, diodes, replicating, flip, surfer, subtle, spectrum
PRACTICE USING THE NEW WORDS.
- Marine animals can detect changes in the electric field around them.
- Only a handful of species have this special ability.
- Each creature uses this sense in a slightly different way.
- Sharks can detect tiny signals and quickly sense them in the water.
- This ability gives them an extra edge when hunting.
- They can detect the heartbeat of their prey.
- Scientists study the anatomy of these animals to understand their senses.
- One researcher found himself fascinated by these unusual organs.
- He spent hours dissecting specimens in the lab.
- Each pore on the skin connects to a sensing structure.
- Tiny spots dot the surface of the ray’s body.
- Inside the canal, there is a jelly-like goo.
- The signal travels to a small pouch at the end.
- The shape looks like a small ancient flask.
- These structures are called ampullae.
- At first, scientists were stumped by their function.
- Researchers are still trying to figure out how the system works.
- This sense is known as electroreception.
- The fish’s skin is covered in mucus.
- Its membranes interact with the surrounding water.
- This creates a measurable electrical phenomenon.
- The signal repeats at a certain frequency.
- It can be as low as a few hertz.
- Rays can tune into specific electrical signals.
- They respond to a particular channel of frequency.
- The signal travels through a narrow canal.
- Many canals cluster together on the head.
- A conductive gel fills each canal.
- Specialized cells detect the signal.
- This allows the animal to spot hidden prey.
- Predators can sneak up on their prey using this sense.
- In experiments, scientists use diodes to create signals.
- They are replicating the electrical patterns of living fish.
- The system can flip between different signals quickly.
- This research may help protect swimmers and surfers.
- The signals detected are extremely subtle.
- Animals may experience a whole spectrum of electrical sensations.
HUMOR – PUNS
Wordplay Classics
- I’m reading a book on anti‑gravity — it’s impossible to put down.
- I used to be addicted to soap, but I’m clean now.
- I stayed up all night wondering where the sun went… then it dawned on me.
- I’m on a seafood diet. I see food and I eat it.
Extra‑ Cheesy (but satisfying)
- I don’t trust stairs. They’re always up to something.
- The rotation of the Earth really makes my day.
- I’d tell you a construction pun, but I’m still working on it.
- I once heard a joke about amnesia, but I forgot how it goes.
Smart‑Kid Science Puns
- Never trust an atom — they make up everything.
- Two antennas got married. The ceremony was okay, but the reception was excellent.
- If you’re bad at math, it’s only natural — you can always count on mistakes.
Dry, Deadpan, Perfect
- I used to play piano by ear, but now I use my hands.
- My friend said he didn’t understand cloning. I told him, “That makes two of us.”
- I bought a belt made of clocks. It was a waist of time.
Animal Puns (because they always land)
- I’m so good at sleeping, I can do it with my eyes closed.
- What do you call a fish with no eyes? Fsh.
- I asked my dog what’s two minus two. He said nothing.
Short, Sharp, One‑Liners
- I have a few jokes about unemployed people, but none of them work.
- I told my suitcase we’re not going on vacation this year. Now I’m dealing with emotional baggage.
- I don’t play soccer because I enjoy the sport — I just do it for kicks.
METHOD
Listen- Comprehension-Read (Vocabulary, pronunciation) -Grammar- Speaking