AccelePrep for the ACT Test 2nd Edition Student Text

C HAPTER 8 | H YPER P REP R EADING • 155

POWER PRACTICE 1

his dual theory of lichens that the true nature of the lichen association began to emerge. Schwendener’s hypothesis, which at the time lacked experimental evidence, arose from his extensive analysis of the anatomy and development in lichens, algae, and fungi using a light microscope. Many of the leading lichenologists at the time rejected Schwendener’s hypothesis because the consensus was that all living organisms lived independently. Other prominent biologists were not so quick to reject Schwendener’s ideas and the concept soon spread into other areas of study. When the complex relationships between pathogenic microorganisms and their hosts were ϐ‹ƒŽŽ› ‹†‡–‹ϐ‹‡†ǡ…Š™‡†‡‡”ǯ• Š›’‘–Š‡•‹• „‡‰ƒ to gain popularity. Lichens play an important role in our environment, and they are a valuable tool for •…‹‡–‹ϐ‹…•–—†›Ǥ Š‡…Š‡‹…ƒŽ• ’”‘†—…‡† „› lichens have been used to make all sorts of products, including dyes, cosmetic ingredients, and homeopathic medicines. Scientists also use lichens to gauge the effects of pollutants in air or water. Because lichens are vulnerable to environmental disturbances, they are used to study the effects of air pollution, ozone depletion, and metal contamination. They help break down material that keeps soil healthy, and they provide food and shelter for all sorts of creatures—big and small. 1. The passage mentions all of the following as being functions of the fungal component of a lichen EXCEPT: A. protecting the lichen from stressful conditions. B. using sunlight to produce sugars to be used for food. C. retaining water for use by both organisms. D. providing a surface area for capturing mineral nutrients. 2. According to the passage, lichens are ’ƒ”–‹…—Žƒ”Ž› —•‡ˆ—Ž ‹ –Š‡ •…‹‡–‹ϐ‹…•–—†› ‘ˆ environmental issues because they are: F. sensitive to environmental changes. G. used in manufacturing various products. H. observable underneath a microscope. J. found in the most extreme conditions.

DIRECTIONS: The passage below is followed by a set of items. Read the passage and choose the best answer for each item. You may refer to the passage as often as necessary to answer the items. Answers are on p. 310. Items #1–5 refer to the following passage. Natural Science: This passage is excerpted from an article about lichens. Lichens (“lie-kins”) are life forms that can grow on surfaces in some of the most extreme environments on earth—from the frozen arctic tundra and scorching hot deserts, to rainforests and steep cliff faces. Lichens are a combination of two organisms living together in a relationship called “symbiosis.” The two partners are algae, such as stoneworts, seaweed, or pond scum, and fungi, such as molds, rusts, or mushrooms. How these two elements form a lichen is one of the great puzzles in biology. But their partnership is a successful one, as there are as many as 30,000 lichen species worldwide. Many of these species are quite beautiful and colorful, their appearance looking much like crystals under a microscope. Once joined together, an alga begins using sunlight to make sugars as food for both itself and its fungal partner. The fungus’ job includes protecting them both from intense sunlight and other stresses. Š‹• ’ƒ”–‡”•Š‹’ ‹• ƒ ˜‡”› ‡ˆϐ‹…‹‡– ™ƒ› –‘ ‰‡– nutrients—up to 20 percent of fungus species live in a lichen partnership. The algal or cyanobacterial cells are photosynthetic, and, as in plants, they reduce atmospheric carbon dioxide into organic carbon sugars to feed both the fungus and the alga. Both partners gain water and mineral nutrients, mainly from the atmosphere, through rain and dust. The fungal partner protects the alga by retaining water and serving as a larger capture area for mineral nutrients. This system has worked for –Š‘—•ƒ†• ‘ˆ ›‡ƒ”•ǡ ƒ• Ž‹…Š‡• Šƒ˜‡ ϐ‹‡Ǧ–—‡† –Š‡‹” feeding mechanisms. Although lichens had been recognized as organisms for quite some time, it was not until 1867, when Swiss botanist Simon Schwendener proposed 5 10 15 20 25 30 35

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