NC EOG Practice Test 3

The Plant That Bites Back

¹Most plants get everything they need from sunlight, air, water, and soil. The Venus flytrap is different. This small plant catches and digests insects and spiders. In the whole world, it grows wild in only one small area: the wet, sandy lowlands of North and South Carolina, within about 75 miles of Wilmington, North Carolina.

²Why would a plant need to catch bugs? The answer is in the soil. Flytraps grow in boggy places called wet savannas, where the ground is sandy and soaked. The soggy soil is very poor in nutrients. In particular, it has little nitrogen, which plants use to build healthy leaves and stems. Most plants would struggle there. The flytrap solves the problem by getting nitrogen from the bodies of the animals it catches. It still uses sunlight to make its food, like other plants do. The insects are more like vitamins than meals.

³Each trap is a leaf with two lobes joined by a hinge, like the two halves of a clamshell. Stiff bristles line the edges. On the inside of each lobe are three tiny trigger hairs. When an insect crawls inside, looking for the sweet nectar the trap gives off, it may brush against one of these hairs.

⁴One touch is not enough. The trap shuts only if trigger hairs are touched twice within about 20 seconds. This clever system keeps the trap from wasting energy on a falling raindrop or a bit of blowing leaf, which usually touch a hair only once. A living insect moving around will almost always touch a hair again. When it does, the trap snaps shut in about a tenth of a second.

⁵At first, the trap closes loosely. The bristles cross like the bars of a cage. A very small insect can squeeze out between them, and the trap soon opens again, since such a tiny meal is not worth the effort of digesting. If the insect is too big to escape, its struggling keeps brushing the trigger hairs, and the lobes press tightly together, sealing the trap.

⁶Then digestion begins. The trap fills with juices that slowly break down the soft parts of the insect. This takes about ten days. When it is finished, the trap opens again. Only the hard outer shell of the insect is left, and wind or rain carries it away. A single trap works only a handful of times before it withers, but the plant keeps growing new ones.

⁷Today, the Venus flytrap is in trouble. Much of the wet land where it grows has been drained to build roads, houses, and farms. Fire is also part of the story. Natural fires once swept through the savannas every few years, clearing away taller plants that would otherwise shade the sun-loving flytraps. When fires are stopped, shrubs crowd the flytraps out. Some people also dig up wild plants to sell. In North Carolina, taking a Venus flytrap from the wild without permission is now a serious crime.

⁸In 2005, North Carolina named the Venus flytrap its official state carnivorous plant. Scientists and land managers are working to protect its home, sometimes by setting careful, controlled fires. Their goal is to keep this remarkable plant snapping in the Carolinas for many years to come.