Re-tell Lecture — Marine Biology

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. Bioluminescence in the deep ocean In the deep ocean, where sunlight cannot reach, an astonishing number of organisms produce their own light through a chemical reaction called bioluminescence. The process involves a molecule called luciferin, which emits light when it reacts with oxygen in the presence of an enzyme called luciferase. Different species use bioluminescence for different purposes. Anglerfish dangle a glowing lure to attract prey in the darkness. Squid and shrimp use sudden flashes to startle predators and escape. Some fish produce light on their undersides to match the faint light filtering from above, effectively erasing their silhouette and making them invisible to predators looking up from below, a technique called counter-illumination. Scientists estimate that roughly seventy-five per cent of deep-sea organisms are bioluminescent, making it the most common form of communication in the largest habitat on Earth. Despite its prevalence, much remains unknown about deep-sea bioluminescence because the extreme depth and pressure make observation and collection extremely difficult.

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. Whale migration patterns Many whale species undertake some of the longest migrations in the animal kingdom, travelling thousands of kilometres between feeding grounds in cold polar waters and breeding grounds in warm tropical seas. Humpback whales, for example, feed on krill and small fish in Antarctic waters during summer, then swim north to breed and give birth in the warm, shallow waters near the equator during winter. The journey can exceed eight thousand kilometres each way. Scientists believe whales migrate because the two locations serve different biological needs: cold waters are rich in food but too cold for newborn calves, which lack the thick blubber layer needed for insulation. Warm tropical waters are safer for birth and nursing but offer little food, so mothers fast during this period, living on energy stored as blubber. Navigation over such distances is remarkable. Whales appear to use a combination of the Earth's magnetic field, ocean currents, coastline features, and possibly even the position of the sun and stars to find their way.

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. Plastic pollution and marine life Plastic pollution in the ocean has become one of the most visible environmental problems of our time. An estimated eight million tonnes of plastic enter the ocean every year, where currents concentrate it into enormous floating accumulations like the Great Pacific Garbage Patch. But the visible surface debris is only part of the problem. Over time, sunlight and wave action break plastic into tiny fragments called microplastics, smaller than five millimetres. These particles are now found throughout the water column, from the surface to the deepest ocean trenches, and in the bodies of marine organisms at every level of the food chain. Sea turtles mistake plastic bags for jellyfish, seabirds feed coloured fragments to their chicks, and filter-feeding whales ingest microplastics along with their food. Research has shown that microplastics can carry toxic chemicals on their surfaces, which may accumulate in the tissues of animals that consume them. The long-term effects on marine ecosystems and on humans who eat seafood are still being studied, but early findings are cause for serious concern.