The rate at which pollen settles is dictated principally by the size a

Question

Aristotle RC 99 - Passage 13     
   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 their pollen grains through air cavities in their walls. The grains of many species quickly dehydrate after release.

There is a limit, however, to the lower range of pollen size. The smaller a particle becomes, the more difficult its capture, because as airflow carrying particles sweeps past surfaces, inertia represents a principal component of the mechanism for capture. Usually considered a―primitive‖ feature in textbooks, wind-pollination has, in fact, reappeared independently in many plant groups relatively recently in geological time.

General textbooks still often give the impression that the anemophilous syndrome is rather uninteresting, often defining it mainly as a combination of negatives: a lack of nectar, scent, petals, etc. Wind pollination has traditionally been viewed as a reproductive process dominated by random events—the vagaries of the wind and weather. This view seems justified by the potential hazards a pollen grain is subject to when transported over long distances.

Pollen loss through happenstance is compensated for in wind-pollinated plants to a large degree by pollen-to-ovule ratios that greatly exceed those of insect-pollinated species. And 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 is huge, sticky, and feathery, the better to catch any floating pollen grains. Similarly, wind-pollinated plants typically evolved to grow in stands, such as pine forests, corn fields and grasslands. Indeed the wind vector is only useful in large, near-monoculture populations.

However, recent research has 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. The devices that operate to prevent self-pollination are also sometimes extremely intricate. Many species take advantage of the physics of pollen motion by generating aerodynamic environments within the immediate vicinity of their reproductive organs. Two biological features appear to be critical in this process: the density and size of the pollen grain and the morphology of the ovulate organ.

The shape of the female organ creates patterns of airflow disturbances through which pollen grains travel. The obstructing organ causes airflow to separate around windward surfaces and creates turbulence along leeward surfaces as ambient wind speeds increase. Because the geometry of female organs is often species-specific, airflow disturbance patterns that are also species-specific can be generated. The speed and direction of this pattern combines with the physical properties of a species‘ pollen to produce a highly synergistic pattern of pollen collision on windward surfaces and sedimentation on leeward surfaces of reproductive organs. The aerodynamic consequences of this synergism can significantly increase the pollen-capture efficiency of an ovulate organ   1 
 1. In general, according to the author of the passage, pollen grains that would have the greatest dispersal range would have which of the following characteristics?

I. Small size
 II. Dryness
III. Low-density

A. I only
 B. I and II only
 C. I and III only
 D. I, II and III
 E. II and III only

2 
 2. Which of the following is the tone of the passage, in the most part?

A. Critical
 B. Descriptive
 C. Laudatory
 D. Humorous
 E. Condescending

3 
 3. Based on the information set forth in the passage, all the following mechanisms serve to reduce pollen loss in wind-pollinated plants EXCEPT:

A. retention of pollen within the male organ when weather conditions are not conducive to dispersal.
 B. growth of plants in large populations with few species. 
C. creation of species-specific air-flow disturbance patterns by the morphology of the ovulate organ.
 D. development of intricate mechanisms to prevent self-pollination.
 E. high pollen-to-ovule ratios

4 
 4. Based on passage information, it is reasonable to conclude that windpollinated plants are LEAST likely to be found:

A. in tropical rain forests of South America.
 B. in the taiga and other northern European coniferous forests.
 C. in the valleys of California.
 D. along river banks in temperate climates
 E. on the windy slopes of the Himalayas

SeaGul · Accepted Answer

I don't agree with the OA for #3 - there is nothing about exactly  "male organ"  - so answer A should be correct.
what about D - anyway it is transferable from the text, you can compare "development of intricate mechanisms to prevent self-pollination" and "The devices that operate to prevent self-pollination are also sometimes extremely intricate". So answer D is not.

carcass · Answer

Replying to a private message

A) It is stated

B) It is stated

C) It is stated

D) It is not stated anywhere

E) It is stated

Hope this helps.

Regards

chetandhemre · Answer

Option (D) talks about Pollen capture efficiency, whereas we are asked in the question about the Pollen Loss.
Reverting back to the point of reference takes us to the 3rd Paragraph. Whereas Option D is found in the 5th paragraph.
The point of reference and the description of both the para's do not match. Hence, D.
Open for counter.

PearlRay · Answer

Please explain the OE of Q3 and Q4 for this passage?

naveens222 · Answer

Q3 is explained by Carcass above
Q4: My 10 cents
The question says that "it is reasonable to conclude that" and also most part of the passage describes about the wind and the effect of its speed on pollination.
I believe he is looking for places where the likely hood of wind carrying away the seeds is less. 
1) Tropical rainforests would have less wind and also humidity wouldn't remove the weight from seeds, making it less for wind pollination.
Other options imply a more windy environment at their locations 
ex: option 2 says that "European coniferous forests" which have usually long trees and more wind.
Hope this makes any sense.

Gmatsaiyan · Answer

Topic and Scope  - discusses the evolution and unique adaptations of wind pollination.
 Mapping the Passage 
¶s1 and 2 describe adaptations specific to pollen grain size.
¶s2 and 3 elaborate on the traditional view of wind pollination as primitive and suggest that wind pollination has independently evolved several times.
¶4 describes wind pollination and the traditional view of it.
¶5 describes recent evidence and introduces two sophisticated features of wind pollination: pollen grain size and ovulate organ morphology.
¶6 describes adaptations specific to ovulate organ morphology.

Gmatsaiyan · Answer

Answers and Explanations OE 
 1) Where does the author discuss pollen grains? Go back to ¶s1 and 2. Since the Roman Numeral choices are fairly short, it‘s probably fastest in this case not to worry about searching for the one that appears most frequently; start in order. The author discusses in ¶s1 and 2 that small, low-density grains are preferable, which validates RNs I and III. Dryness can be inferred from the author‘s point that many pollen grains ―quickly dehydrate after release.‖ Therefore, all RNs are valid and the
answer choice must be (D). 
(A): Opposite. As described above.
(B): Opposite. As above.
(C): Opposite. As above.
(D): The correct answer
(E): Opposite. As above.
 2) The passage is primarily describing wind pollination and related concepts. ‗B‘ captures this very well
(A): The author is not criticising anything in the passage
(B): The correct answer
(C): The author is not praising anything in the passage
(D): There is no humour in the passage
(E): The passage does not ‗condescend‘ or look down upon anything
 3) A scattered detail question. You‘re looking for an answer choice that doesn’t function to prevent pollen loss. While three of the choices can be eliminated based on the text of the passage, (D) is an adaptation with an entirely different function. Preventing self-pollination is never discussed in the context of pollen loss; it‘s useful only to prevent inbreeding.
(A): Opposite. This is mentioned in ¶4.
(B): Opposite. This paraphrases the author‘s point in ¶3 that ―the wind vector is only useful in large, near-monoculture populations.‖
(C): Opposite. This is the topic of ¶6, which is focused with adaptations necessary for pollen capture.
(D): The correct answer
(E): Opposite. This is mentioned in ¶4.
 4) Predict: where would wind pollinated plants not do well? Probably in a place without much wind and with lots of moisture. (A) looks good: tropical rain forests certainly match both these criteria.
(A): The correct answer
(B): Opposite. This is a dry, windy biome. Perfect for wind pollination. Conifers are specifically mentioned in the passage as wind pollinators.
(C): Opposite. The author mentions certain plants in central California valleys in ¶2 as having recently adapted to wind pollination.
(D): Opposite. Since the plants are right by a riverbank, they might be less likely to wind pollinate, but they would still be far more likely to use wind pollination by a river (which doesn‘t guarantee humidity) than in a tropical rain forest (which does).
(E): Opposite. Windy places are ideal for wind pollination.

Aadi01 · Answer

Hi, Is there any source of glossary related to Natural Sciences Biology and other Hectic topics like this. I am not a biology stundent and it is very difficult to understand such passages

Aadi01 · Answer

Also, is there any strategy to solve  A scattered detail question  . These are quite exhaustive and time taking

Naman18 · Answer

A. retention of pollen within the male organ when weather conditions are not conducive to dispersal....where it has been written in the passage?

MartyTargetTestPrep · Answer

That is not mentioned anywhere in the passage. Question 3 is busted.

trulyness · Answer

MartyTargetTestPrep  Also, what about Q 4? Can it be solved without bringing in any additional information from outside the passage? All that is given in the passage is:

Please help.

Vanshgarg · Answer

I too marked A with same logic.

VerbalBot · Answer

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The rate at which pollen settles is dictated principally by the size a

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The rate at which pollen settles is dictated principally by the size a

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