With the Evolution of Terrestrial Life About 400 Million Years Ago, Wind Replaced Water

Reading Passage Question

With the evolution of terrestrial life about 400 million years ago, wind replaced water as the primary vector by which plants moved male sex cells. Wind pollination has traditionally been viewed as a reproductive process dominated by random events—the vagaries of wind and weather. Pollen loss through happenstance is compensated for in wind-pollinated plants by pollen-to-ovule ratios that greatly exceed those of insect-pollinated species. Unlike the sticky pollen grains of plants pollinated by insects, the pollen grains of wind-pollinated plants are smooth and dry, to avoid clumping and precipitating, and the stigma of the female plant is large and sticky, the better to catch any floating pollen grains. Similarly, wind-pollinated plants typically evolved to grow in stands, such as cornfields, grasslands, or other large, near-monocultural populations.

While wind pollination is usually considered a “primitive” feature by textbooks, recent research has, in fact, shown that several remarkably sophisticated mechanisms for dispersal and capture are characteristic of wind-pollinated plants. Pollen release is often tied to the recognition of unambiguous environmental clues; thus, many plants will not release pollen when wind speeds are low or while humid conditions exist, which might cause pollen grains to clump and fall. The devices that operate to prevent self-pollination are also at times extremely intricate.

Recent findings have revealed another intricacy that compensates for wind pollination’s inefficiency—the physics of pollen motion. The rate at which pollen settles is dictated principally by the size and density of the grain. The slower the settlement rate, the greater the dispersal range. Numerous species reduce the density of pollen grains with air cavities in their walls. There is a limit, however, to the lower range of pollen size.

“ With the evolution of terrestrial life about 400 million years ago, wind replaced water” - is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 4 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

1. According to the author, pollen grains that would have the greatest dispersal range would have which of the following characteristics?

1. Small size
2. Dryness
3. Low-density

1. I only
2. II only
3. I and II only
4. I and III only
5. I, II, and III

2. If rainfall levels in a particular growing season were abnormally high, it is most reasonable to conclude, based on the passage, that the

1. amount of pollen released by wind-pollinated species would be less than normal because of sophisticated mechanisms tied to environmental clues
2. amount of pollen released by wind-pollinated species would be greater than normal to compensate for the greater resulting pollen loss
3. pollen-to-ovule ratios of wind-pollinated species would be unaffected by the change in weather
4. amount of seed produced and released by wind-pollinated species would be greater than normal
5. amount of pollination carried by insect pollinators would remain unchanged

3. According to the passage, all the following mechanisms serve to reduce pollen loss in wind-pollinated plants EXCEPT:

1. development of a large specially shaped stigma
2. retention of pollen within the male organ when weather conditions are not conducive to dispersal
3. growth of plants in large populations with few species
4. development of intricate mechanisms to prevent self-pollination
5. efficient design of the airborne pollen grain

4. The author’s attitude towards textbooks that describe wind pollination as “primitive” is best described as one of

1. reasoned rejection
2. tempered uncertainty
3. vehement disagreement
4. mild displeasure
5. complete support

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