托福口语 Task 4

Today we're going to talk about a fascinating adaptation in the animal kingdom: the ability of some creatures to survive extreme dehydration. This is called anhydrobiosis, which literally means 'life without water.' The main point I want to emphasize is that anhydrobiosis is not just about withstanding dryness, but about entering a reversible state of suspended animation that allows the organism to resume normal activity once water returns. Let me give you two examples. First, consider the tardigrade, also known as the water bear. These tiny creatures live in mosses and lichens. When their habitat dries up, they curl into a ball, expel almost all water from their bodies, and produce a special sugar called trehalose that protects their cell membranes. In this state, they can survive for decades, even in the vacuum of space. When water is added, they rehydrate and become active within hours. Second, take the resurrection fern, a plant found in dry regions. During drought, its leaves curl and turn brown, and it loses up to 97% of its water. But its cells produce proteins that stabilize the cell structure. Once rain falls, the fern uncurls, turns green, and resumes photosynthesis within a day. So, both animals and plants use anhydrobiosis to survive harsh dry periods, and they can fully recover when conditions improve.