PTE Listening Practice Test 13

"Today I want to talk about coral bleaching, one of the most visible signs of stress in the world's oceans. Corals are animals, but they depend on tiny algae living inside their tissues, which produce food through photosynthesis and give corals their bright colours. When the water becomes unusually warm, even by just one or two degrees for several weeks, this partnership breaks down and the coral expels the algae. Without the algae, the coral's white skeleton shows through its transparent tissue, which is why we call this process bleaching. Bleached corals are not dead, and if temperatures return to normal quickly, the algae can return and the coral may recover. However, if the heat lasts too long, the coral starves, and the entire reef community, including the fish that depend on it, begins to collapse. Because bleaching events are becoming more frequent as ocean temperatures rise, scientists are testing heat-tolerant corals and restoration techniques to give reefs more time to adapt."

কোরাল তার ভেতরের শৈবালের ওপর নির্ভর করে। পানি অস্বাভাবিক গরম হলে কোরাল শৈবাল বের করে দেয় এবং সাদা হয়ে যায় — একে ব্লিচিং বলে। তাপমাত্রা দ্রুত স্বাভাবিক হলে কোরাল বাঁচতে পারে, নইলে পুরো প্রবাল প্রাচীর ধ্বংস হয়। বিজ্ঞানীরা তাপ-সহনশীল কোরাল নিয়ে গবেষণা করছেন।

"Many parents worry that raising a child with two languages might confuse them or slow down their speech. In fact, research suggests that bilingual children reach their main language milestones at roughly the same ages as children who speak only one language, even if they sometimes mix words from both languages early on. Some studies have found that bilingual people are better at switching attention between tasks, perhaps because their brains constantly manage two competing language systems. There is also evidence that lifelong bilingualism may delay the onset of dementia symptoms by several years, although it does not prevent the disease itself."

"Rooftop gardens are spreading across crowded cities, from Dhaka to Singapore. Covering a roof with soil and plants keeps the building below noticeably cooler in summer, which can reduce the need for air conditioning. The plants also absorb rainwater, easing pressure on drains during heavy storms, and provide fresh vegetables for residents. The main obstacles are the cost of waterproofing and the need to check whether an older roof can safely carry the extra weight."

"Teenagers are often criticised for going to bed late and struggling to get up in the morning. But sleep researchers point out that during adolescence the body's internal clock naturally shifts later, so many teenagers genuinely do not feel sleepy until around eleven at night. When schools start very early, these students lose sleep they cannot easily make up. Several school districts that moved their start times later reported better attendance and fewer car accidents involving teenage drivers."

"When a honeybee finds a good source of nectar, it returns to the hive and performs a special movement known as the waggle dance, in which the angle and length of the dance tell the other bees where the food is located."