Table of Contents
BEST IELTS General Reading Test 479
IELTS GENERAL READING TEST 479 – PASSAGE – 2
IELTS GENERAL READING TEST
READING PASSAGE – 2
Gills
A. Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids, and ammonia. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide.
B. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing counter-current exchange. The gills push the oxygen-poor water out through openings in the sides of the pharynx. Some fish, like sharks and lampreys, possess multiple gill openings. However, bony fish have a single gill opening on each side. This opening is hidden beneath a protective bony cover called the operculum. Juvenile bichirs have external gills, a very primitive feature that they share with larval amphibians.
IELTS General Reading Test
C. Previously, the evolution of gills was thought to have occurred through two diverging lines: gills formed from the endoderm, as seen in jawless fish species, or those form by the ectoderm, as seen in jawed fish. However, recent studies on gill formation of the little skate (Leucoraja erinacea) have shown potential evidence supporting the claim that gills from all current fish species have in fact evolved from a common ancestor.
D. Air breathing fish can be divided into obligate air breathers and facultative air breathers. Obligate air breathers, such as the African lungfish, are obligated to breathe air periodically or they suffocate. Facultative air breathers, such as the catfish Hypostomus plecostomus, only breathe air if they need to and can otherwise rely on their gills for oxygen. Most air breathing fish are facultative air breathers that avoid the energetic cost of rising to the surface and the fitness cost of exposure to surface predators.
IELTS General Reading Test
E. All basal vertebrates breathe with gills. The gills are carried right behind the head, bordering the posterior margins of a series of openings from the esophagus to the exterior. Each gill is supported by a cartilaginous or bony gill arch. The gills of vertebrates typically develop in the walls of the pharynx, along a series of gill slits opening to the exterior. Most species employ a counter-current exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other.
F. The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange. When a fish breathes, it draws in a mouthful of water at regular intervals. Then it draws the sides of its throat together, forcing the water through the gill openings, so that it passes over the gills to the outside. The bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate antecedent no doubt had more arches, as some of their chordate relatives have more than fifty pairs of gills.
IELTS General Reading Test
Questions 15-20
Choose the correct heading for the given sections from the list of headings below.
Write the correct number in the answer sheet.
List of Headings
i. Location of the organ that is responsible for fish breathing.
ii. Increased external side of protein structures for swapping oxygen and carbon dioxide.
iii. Gills are more robust than lungs in terms of breathing capacity.
iv. Current studies clarifying the development of gills.
v. An ancestral specie having more gills.
vi. Divergent air breathing fish compared.
vii. Air breathing fish are faster in water than fish that breath through gills.
viii. Some marine species have numerous gill slots.
ix. The evolution of the gills has resulted in better reproduction.
IELTS General Reading Test
15. Paragraph A
16. Paragraph B
17. Paragraph C
18. Paragraph D
19. Paragraph E
20. Paragraph F
IELTS General Reading Test
Read the text below and answer questions 21-26.
Maize
The maize is also known as corn in North American and Australian English. It is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The leafy stalk of the plant produces pollen inflorescences and separate ovuliferous inflorescences called ears that yield kernels (seeds), which are fruits. Maize has become a staple food in many parts of the world, with the total production of maize surpassing that of wheat or rice. In addition to being consumed directly by humans (often in the form of masa), maize is also used for corn ethanol, animal feed and other maize products, such as corn starch and corn syrup.
The six major types of maize are dent corn, flint corn, pod corn, popcorn, flour corn, and sweet corn. Sugar-rich varieties called sweet corn are usually grown for human consumption as kernels, while field corn varieties are used for animal feed, various corn-based human food uses (including grinding into cornmeal or masa, pressing into corn oil, and fermentation and distillation into alcoholic beverages like bourbon whiskey), and as chemical feedstocks. Maize is also used in making ethanol and other biofuels.
IELTS General Reading Test
Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. In 2014, total world production was 1.04 billion tonnes. Maize is the most widely grown grain crop throughout the Americas, with 361 million metric tons grown in the United States alone in 2014. Genetically modified maize made up 85% of the maize planted in the United States in 2009.
Subsidies in the United States help to account for its high level of cultivation of maize and its position as the largest producer in the world. The maize plant is often 3 m in height, though some natural strains can grow 13 m. The stem is commonly composed of 20 internodes of 18 cm length. The leaves arise from the nodes, alternately on opposite sides on the stalk. A leaf, which grows from each node, is generally 9 cm in width and 120 cm in length.
IELTS General Reading Test
Ears develop above a few of the leaves in the midsection of the plant, between the stem and leaf sheath, elongating by around 3 mm per day, to a length of 18 cm with 60 cm being the maximum alleged in the subspecies. They are female inflorescences, tightly enveloped by several layers of ear leaves commonly called husks. Certain varieties of maize in the past were bred to produce many additional developed ears.
These are the source of the “baby corn” used as a vegetable in Asian cuisine. The apex of the stem ends in the tassel, an inflorescence of male flowers. When the tassel is mature and conditions are suitably warm and dry, anthers on the tassel dehisce and release pollen. Maize pollen is anemophilous (dispersed by wind), and because of its large settling velocity, most pollen falls within a few meters of the tassel.
IELTS General Reading Test
Elongated stigmas, called silks, emerge from the whorl of husk leaves at the end of the ear. They are often pale yellow and 18 cm in length, like tufts of hair in appearance. At the end of each is a carpel, which may develop into a “kernel” if fertilized by a pollen grain. The pericarp of the fruit is fused with the seed coat referred to as “caryopsis”, typical of the grasses, and the entire kernel is often referred to as the “seed”.
The cob is close to a multiple fruit in structure, except that the individual fruits never fuse into a single mass. The grains are about the size of peas, and adhere in regular rows around a white, pithy substance, which forms the ear.
IELTS General Reading Test
The maximum size of kernels is reputedly 2.5 cm. An ear commonly holds 600 kernels. They are of various colours: blackish, bluish-grey, purple, green, red, white, and yellow. When ground into flour, maize yields more flour with much less bran than wheat does. It lacks the protein gluten of wheat and, therefore, makes baked goods with poor rising capability.
A genetic variant that accumulates more sugar and less starch in the ear is consumed as a vegetable and is called sweet corn. Young ears can be consumed raw, with the cob and silk, but as the plant matures, the cob toughens and the silk dries to inedibility. By the end of the growing season, the kernels dry out and become difficult to chew without cooking them tender first in boiling water.
IELTS General Reading Test
Questions 21-26
Write no more than TWO WORDS and/or numbers for each answer.
21. The grassy tail of the maize plant delivers pollens that produce …………………..
22. The total production of maize outstripping wheat and rice has made it a ………………….. in many countries.
IELTS General Reading Test
23. …………………..are offered in United States that encourages the farming of maize.
24. Some variations of maize have been ………………….. to yield vegetables like baby corn.
25. If inseminated by a pollen, the carpel may evolve in a …………………..
26. The cob of the sweetcorn ………………….. as the plant mellows.
IELTS General Reading Test
IELTS General Reading Test
ANSWERS
15. II
16. VIII
17. IV
18. VI
19. I
20. V
21. KERNELS OR SEEDS
22. STAPLE FOOD
23. SUBSIDIES
24. BRED
25. KERNEL
26. TOUGHENS
IELTS General Reading Test