Passage 2 | Agriculture
Plants reproduce when genetic material from the male reproductive organ, the anther, is transferred to the female reproductive organ, the carpel. This process is called pollination, a reference to the pollen (the male sex cell) that is carried to the carpel. Some plants are self-pollinators and do not require any outside help to transfer pollen grains from the male anther to the female carpel. Many plants, however, rely on external pollinating agents like water, wind, animals, and, most often, insects to assist with pollination.
In human agricultural activities, successful external pollination is essential because plants produce fruits and vegetables only when pollination occurs. There are three methods for accomplishing such agricultural pollination. The first method is “natural pollination,” carried out most commonly by birds and wild insects that happen to move pollen between flowers as they visit different blossoms to feed. The process is quite accidental, but it nevertheless successfully spreads genetic material among the plant population.
As the term implies, natural pollination has been going on for a long time without human interference. However, in modem U.S. food production, this method alone is no longer sufficient to fertilize all the plants involved. This is because current agricultural practices often encourage the seeding of large fields with a single crop, thus reducing the diversity of the land. Since there is only one kind of food and one kind of habitat, the amount of species that find the land suitable is severely limited, and many natural pollinators are forced to vacate the area. Furthermore, because all the plants in a single-crop field bloom at the same time, dense concentrations of pollinators are needed, but only for a short amount of time, while, during the rest of the year, the field does not offer enough food to support these natural pollinators. Other factors contributing to the failure of natural pollination include modern human activities such as logging, pesticide use, and urban growth, as well as natural factors like insect diseases, all of which are causing natural pollinators to disappear.
In order to ensure the continued productivity of their crops, growers have had to find other ways of pollinating their fields. Managed pollinators and artificial pollination offer two solutions to the problem of disappearing natural pollinators. “Managed 5 pollinators” is a term ascribed to bees that are cultivated for the specific purpose of agricultural pollination. Although many kinds of bees are used as managed pollinators, the most common variety is the honeybee. Honeybees collect pollen and store it using “pollen baskets,” which are located on their back legs. This means that they can gather more pollen at each blossom, and that more will be accidentally distributed as they travel from flower to flower.
Fruit and vegetable growers all over the United States contract with beekeepers, hiring the services of honeybees to pollinate their fields.[A] In the United States agricultural i industry, ninety different crops rely on honeybees for pollination, but the crop requiring the most bees is the California almond. [B] In total, this industry uses one million hives—almost half the U.S. population rs of managed honeybees. [C] Managed pollinators like honeybees are an important alternative to natural pollination, but the main drawback is that managed honeybee populations are susceptible to the same factors—such as harmful pesticides and insect diseases—that have reduced natural pollinator populations. [D] The worst threat to the survival of honeybees is the Varroa mite, a parasite that has destroyed 95 to 98 percent of the wild honeybee population. Although cultivated honeybees are somewhat protected because humans provide them with sheltered environments and use chemicals to ward off mites, they are still at risk.
“Artificial pollination” is another alternative to natural pollination. This method accomplishes pollination through artificial techniques, eliminating the need for natural or managed pollinators like honeybees. One such technique currently in use is called electrostatic pollination. Past studies have revealed that pollinating insects like bees have an electrostatic charge that causes pollen to cling to their bodies. Scientists applied this information to test and develop this artificial pollination method. They introduced an electrostatic charge to test plants and then dusted charged pollen grains over them. They found that the pollen was electrostatically :: attracted to the plants, which increased the rate of pollination and led to larger crop yields. The downside is that the quality of electrostatically pollinated crops is slightly reduced. Vet, it is nonetheless an important s option for agricultural growers, considering the lack of natural pollinators and the risks facing the populations of managed pollinators.
14. The word external in the passage is closest in meaning to
15. According to paragraph 1, what is pollination?
(A) The ability to reproduce without any assistance
(B) The transfer of pollen from plants to insects
(C) The use of pollinating agents in the reproductive process
(D) The movement of sex cells from the anther to the carpel
16. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
(A) Many pollinators are needed to pollinate single-crop fields, which contain plants that come into bloom all at once.
(B) In a single-crop field, sometimes there are more blossoms than can be used, and other times pollinators are without food.
(C) A single-crop field cannot rely on natural pollinators alone, so other methods of pollination must be used to help the field produce a harvest.
(D) After a single-crop field blooms, natural pollinators are unable to find enough food to survive.
17. According to paragraph 4, “managed pollinators” are
(A) domesticated bees that are raised to pollinate commercial crops
(B) not capable of meeting the needs of agricultural pollination
(C) primarily used in research to develop artificial pollination methods
(D) not as useful to farmers for pollination as honeybees are
18. In paragraph 5, why does the author mention California almond?
(A) To support the claim that honeybees are the most important pollinator
(B) To suggest that managed pollinators are ineffective in U.S. agriculture
(C) To introduce artificial pollination as a method of agricultural pollination
(D) To give an example of a large crop that honeybees help pollinate
19. The word susceptible in the passage is closest in meaning to
20. The passage identifies all of the following as threats to populations of natural pollinators EXCEPT
(A) human activities related to industrialization, construction, and urban development
(B) temperature changes caused by shifts in climate and season
(C) natural infestations of honeybee hives by harmful bee parasites
(D) the use of pesticides on plants and fields cultivated for agricultural purposes
21. The word cling in the passage is closest in meaning to
22. The word them in the passage refers to
23. According to paragraph 6, what is the function of a honeybee’s electrostatic charge?
(A) It helps the honeybee locate the flowers with the most pollen.
(B) It is a form of navigation used by many varieties of bees.
(C) It causes plants to become electrostatically charged.
(D) It attracts pollen from the flower to the honeybee’s body.
24. Look at the four squares m that indicate where the following sentence could be added to the passage.
Another crop that requires large amounts of honeybees is the Maine blueberry, which uses 50,000 hives yearly for the purpose of pollination.
Where would the sentence best fit?
25. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Pollination takes place when pollen is carried from one part of a plant to another, and this process has occurred naturally for thousands of years.
(A) The amount of fruits and vegetables that are produced by agricultural crops depends on the amount of pollination that takes place.
(B) Modern human practices, such as creating single-crop fields, have led to the failure of natural pollination in many cases.
(C) Farmers throughout the United States employ large concentrations of honeybees to pollinate their fields, a process known as managed pollination.
(E) Scientists use artificial pollination techniques to control the levels of electrostatic charge present in plants and pollen.
(D) Managed pollination has become impractical because a sizable portion of the honeybee population has been destroyed by parasites.
(F) Artificial pollination methods such as electrostatic pollination offer an alternative to the use of insects that are vulnerable to diseases and environmental changes.