GMAT Exam Dumps : Graduate Management Admission Test (2022)

Parasitic wasps propagate by injecting their eggs into a caterpillar that then becomes paralyzed as the eggs inside develop into wasp larvae. The wasp larvae kill the caterpillar host as they feed on it, form cocoons, and finally develop into wasps. In attempting to discover how such wasps detect the presence of the caterpillar hosts that are so critical to the wasps' propagation, researchers have uncovered an intriguing defense mechanism developed by the plants on which the caterpillars feed.

When chewed on, many plants release volatile compounds from both damaged and undamaged tissues. When these compounds are toxic to the insects that feed on the plants, they can help defend the plants from such attacks. However, the plants on which the wasps' caterpillar hosts feed have evolved an even more complex defense: the caterpillar-infested plants appear to release volatile chemicals that attract parasitic wasps, which then prey on the caterpillars. Scientists originally suspected that the wasps were attracted by an odor, reminiscent of cut grass, that is released as the caterpillar feeds, but a recent study suggests that a different set of volatile attractants is involved. In this study, when researchers used a razor blade to mimic caterpillar damage on the leaves, only grassy odors were emitted, not the volatile compounds that attracted wasps. However, when oral secretions from the caterpillars were applied to these damaged leaves, the leaves released the wasp attractants several hours later. Further tests revealed that oral secretions placed on the razor-damaged leaves stimulated the release of such attractants, making the plants as attractive to wasps as plants that had suffered actual caterpillar damage. These results suggest that chemicals from the caterpillar must be present for these attractants to be released and that unlike the grassy scent, which emanates only as the caterpillar on the plant, the wasp attractants are produced several hours after the attack and persist for several hours, perhaps days. Researchers have launched additional studies to determine whether the wasps' capacity to prey on caterpillars can be enhanced to the extent that the wasps could be used as a natural pesticide to "police" plants and protect them from crop-destroying caterpillars.

Previously unknown extrasolar planets-planets outside our solar system— probably await discovery In archival images taken by the Hubble Space Telescope. A new technique allows astronomers to model the amount and distribution of scattered light produced by young stars suspected of spawning planets and remove that light from images of those stars. Once the glare of the parent stars' light is removed, planets may show up In Images already taken by Hubble's infrared cameras, since heat emitted by planets produces telltale wavelengths of infrared light.

In 2008, astronomers using powerful Earth-based telescopes were able to detect three planets orbiting the star HR 8799 that were not previously detected by astronomers who examined infrared Hubble images of the star in 1998. David Lafrentere—a member of the team of astronomers who detected the planets in 2006 —then applied the new technique to those Hubble images and managed to uncover the outermost of the three planets. The others, tying closer to the star, still could not be distinguished against the background of the star's light.

Lafrenifre's work has helped reaffirm the importance of maintaining long-term archives, and—because Hubble's infrared cameras record some wavelengths of light that cannot penetrate through the atmosphere to reach Earth's surface-revealed new information about the outermost of HR 8799's planets.