2022_심화영어

162 Appendices they can regenerate entire limbs or other body parts that have been detached for various reasons. For example, planarians, a kind of flatworm, have a surprising capacity to regenerate. As little as half or even less of an individual can regenerate into another specimen. And some species of starfish exhibit regenerative capacity when an arm is lost. They can either regrow a lost limb or spawn an entirely new individual from a detached body part. The zebrafish also stands out for the regenerative capacity of its tail fin and heart. Finally, certain lizards can voluntarily detach part of their tail to distract predators. Regeneration then begins, but the new tail does not usually grow back as long as the original one. Ready to Read A. Topic Preview p. 44 2 . M: We are going to learn about telomeres today. Have you heard of them? W: I haven’t. It’s not a familiar word. M: Well, telomeres are among your cells’ smallest structures. They protect the ends of chromosomes and keep them separated from one another in the DNA sequence. Do you know how many pairs of chromosomes every cell in our body has? W: Yes, 23 pairs. M: Right. Every cell in your body has 23 pairs of chromosomes, for a total of 46. And each one of them has a telomere at both ends―92 of these tiny caps per cell in all. W: Why are telomeres important? M: Telomeres directly influence how healthy each newly produced body cell will be. More importantly, telomeres are a yardstick for measuring human aging at the cellular level. Each time a cell divides, the telomere becomes shorter. That means as we get older and our cells have experienced more and more divisions, the telomeres become shorter and shorter. W: Then, that means people with longer telomeres will live longer than those with shorter telomeres? your eyes and rest. M: Thank you. Lesson 2 The Secret to Immotalilty Interactive Communication Listen andWrite p. 41 W: Michael, you know tortoises live really long lives, don’t you? M: Yes, I’ve heard that before. W: Do you know how old the oldest tortoise in the world is? M: I don’t know exactly, but I think they live much longer than humans. W: Yes, exactly. Look at this picture. This tortoise’s name is Jonathan. He is a Seychelles giant tortoise and is thought to be about 190 years old. That would make him the oldest living land animal in the world. M: ‌That would mean he was born in the 1800s. W: Right. Jonathan is believed to have been born in 1832. But his estimated age is based on the fact that he was fully mature when he was brought to St. Helena from the Seychelles in 1882 as a gift to its then-governor. In other words, he could potentially be even older than 190 years old. M: That’s hard to believe. Is he still healthy now? W: Jonathan is blind and has no sense of smell, so he is unaware of food if it is simply placed on the ground. His hearing, however, is excellent, and he responds to the sound of his doctor’s voice. Active Communication Communication Task 1 p. 42 1 . W: Hello, everyone. I have an interesting topic today. Have you heard about animals that have incredible abilities that humans do not possess? In the animal kingdom, there are some species that are able to regenerate to a greater degree than others. More than simply regenerating new skin over a wound,