The Structure of the Feet and Legs Varies Greatly Among Frog Species

Reading Passage Question

The structure of the feet and legs varies greatly among frog species, depending in part on whether they live primarily on the ground, in water, in trees, or in burrows. Frogs must be able to move quickly through their environment to catch prey and escape predators, and numerous adaptations help them do so.

Many frogs, especially those that live in water, have webbed toes. The degree to which the toes are webbed is directly proportional to the amount of time the species lives in the water. For example, the completely aquatic African dwarf frog (Hymenochirus sp.) has fully webbed toes, whereas the toes of White's tree frog (Litoria caerulea), an arboreal species, are only a half or a quarter webbed. Arboreal frogs have "toe pads" to help grip vertical surfaces. These pads, located on the ends of the toes, do not work by suction. Rather, the surface of the pad consists of interlocking cells, with a small gap between adjacent cells. When the frog applies pressure to the toe pads, the interlocking cells grip irregularities on the substrate. The small gaps between the cells drain away all but a thin layer of moisture on the pad, and maintain a grip through capillarity. This allows the frog to grip smooth surfaces, and does not function when the pads are excessively wet.

In many arboreal frogs, a small "intercalary structure" in each toe increases the surface area touching the substrate. Furthermore, since hopping through trees can be dangerous, many arboreal frogs have hip joints that allow both hopping and walking. Some frogs that live high in trees even possess an elaborate degree of webbing between their toes, as do aquatic frogs. In these arboreal frogs, the webs allow the frogs to "parachute" or control their glide from one position in the canopy to another.

Ground-dwelling frogs generally lack the adaptations of aquatic and arboreal frogs. Most have smaller toe pads, if any, and little webbing. Some burrowing frogs have a toe extension—a metatarsal tubercle—that helps them to burrow. The hind legs of ground dwellers are more muscular than those of aqueous and tree-dwelling frogs.

“The structure of the feet and legs varies greatly among frog species” - is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 5 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. Which of the following best characterizes the main idea of the passage?

1. An introduction mentioning the different frog types is followed by a discussion about the structure and use of webbed feet in arboreal and aquatic frogs and brief mentions of other adaptations.
2. After the first paragraph follow details on how to identify the different types of frogs based on their adaptations.
3. Detailed descriptions of the structure and function of frog toe pads explain how some frogs can “parachute” in the canopy.
4. The role of webbed feet in the survival behaviors of three kinds of frogs is detailed.
5. A general discussion of frog adaptations leads to a core passage concerning the “intercalary structure” common to all frogs.

2. Of the following choices, the best title for this passage is

1. Structure and Function of Frog Foot Webbing and Toe Pads
2. Capillarity and Suction in the Webbed Feet of Frogs
3. Muscular Differences Among Frogs
4. Foot Structure in Arboreal, Aquatic, and Ground-Dwelling Frogs
5. Burrowing Behavior in Frogs

3. According to the passage, webbed feet would most likely be found on which type of frog?

1. arboreal
2. aquatic
3. ground-dwelling

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

4. A frog with a metatarsal tubercle and highly developed hind legs most likely lives

1. in a burrow; the adaptations help the frog dig
2. in the water; the adaptations allow the frog to swim quickly through its environment to catch prey and avoid predators
3. in the trees, occasionally “parachuting”; the adaptations help the frog make safe landings when moving from one position in the canopy to another
4. in the trees, occasionally walking along the ground to get from tree to tree; the adaptations help the frog move quickly to avoid predators and catch prey
5. in areas with many smooth surfaces or where other toe pad adaptations are likely to get excessively wet

5. It may be inferred from the passage that capillarity

1. requires plenty of water to function
2. is a type of suction
3. is the term for interlocking cells on the toe pad
4. works only with thin films of water
5. works even better when found in conjunction with an intercalary structure

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