TOEFL iBT Practice Test 39

Sign: Visitor Parking Maximum stay: 2 hours Monday to Saturday, 8:00 a.m.–6:00 p.m. Permit holders exempt Free parking on Sundays and public holidays Vehicles parked longer than permitted may be fined $60.

Sign: Elevator out of order The elevator in this building is temporarily out of order due to a mechanical fault. A technician has been called and repairs are expected to be completed by Friday. Residents on the upper floors needing assistance with heavy items should contact the building manager at extension 12.

Sea turtles undertake some of the animal kingdom's most impressive long-distance migrations, with some species crossing entire ocean basins between feeding grounds and the specific beaches where they themselves hatched decades earlier, a behaviour known as natal homing. Female loggerhead turtles, for instance, will travel thousands of kilometres to return and lay eggs on the same short stretch of coastline where they emerged from the sand as hatchlings, sometimes located with an accuracy of only a few kilometres despite years spent ranging across open ocean with few obvious landmarks. Researchers now believe turtles accomplish this feat largely through geomagnetic imprinting: hatchlings appear to memorise the unique magnetic signature of their home beach, since Earth's magnetic field varies subtly and predictably by location, and this magnetic map, imprinted early in life, allows adult turtles to navigate back with remarkable precision even after years at sea. Experimental support for this theory comes from studies in which researchers exposed hatchling turtles to magnetic fields simulating different geographic locations far from where the animals were actually hatched; the turtles adjusted their swimming direction as though genuinely responding to that distant location's magnetic signature, behaviour difficult to explain by any mechanism other than an innate sensitivity to magnetic cues. This reliance on magnetic imprinting, however, creates a vulnerability that concerns conservationists: coastal development and other human activity that subtly alters local magnetic conditions, though such effects remain understudied, or gradual shifts in Earth's magnetic field itself over turtle lifespans, could in principle disrupt the accuracy of natal homing in ways not yet fully understood, complicating long-term conservation planning for a group of species already threatened by habitat loss and fishing bycatch.