Latihan: Literasi Bahasa Inggris Dasar 2

Text 1: The Animal That Refuses to Die

Tardigrades, sometimes called “water bears,” are tiny animals, most of them less than a millimeter long, that live almost everywhere: in moss on rooftops, in the sand of beaches, in the mud at the bottom of lakes. Under a microscope they look like plump, slow-moving bags with eight stubby legs, each ending in small claws. They need a thin film of water around their bodies to be active, to eat, and to reproduce.

What has made tardigrades famous is what happens when that water disappears. As the moss they live in dries out, many tardigrades pull in their legs and head, curl into a compact shape known as a “tun,” and lose almost all the water in their bodies. Their metabolism slows to a point that is barely measurable. In this state they can survive conditions that would quickly kill most other animals, including extreme cold, high doses of radiation, and, in one 2007 experiment, about ten days of exposure to open space in orbit around the Earth.

How do they do it? Part of the answer lies in special proteins. Researchers have found that some tardigrade species produce proteins that, as the animal dries, form a glass-like material inside its cells. This material appears to hold the cell’s delicate structures in place until water returns. Another protein seems to shield the animal’s DNA from damage.

Popular articles often describe tardigrades as nearly indestructible, but this picture is misleading. Tardigrades survive these extremes only in the tun state, and only for limited periods; an active, water-filled tardigrade is far more fragile. Most of them spend their lives quietly in a patch of damp moss. Their real lesson for scientists is not invincibility but the possibility of pausing life and starting it again.