TOEFL IBT Listening Practice Test 12 Solution, Explanation & Transcripts

Questions 23 through 28.

Listen to part of a talk in a biology class.

The bird’s bill is composed of a homy sheath over a bony core. The entire structure has evolved in numerous ways to the specialized needs of its owner. The bird’s bill is highly modified for a variety of activities such as cutting and crushing seeds, probing tree crevices for insects, drinking nectar from flowers, catching fish, and so on. There’s a large variety in the diets of birds throughout the world. Different birds have evolved different bill types to assist in their feeding. What I mean is, the shape of the bird’s bill is specially adapted to specific foods.

A large number of birds are primarily seed eaters. These birds typically have stout, coneshaped bills and strong jaw muscles for crushing seeds. The edible kernel of a seed is protected by a husk, or shell, which must be removed before the seed can be digested. The smaller finches, sparrows, and grosbeaks use their heavy conical bills to process seeds by removing the outer covering before swallowing them. Larger birds, such as pigeons and pheasants, swallow seeds whole and rely on grit in the gizzard to remove the husks and crush the seeds.

A wide variety of birds are nectar drinkers. These birds prefer the sweet liquid nectar of flowering plants. The co-evolution of birds and flowers has led to specialization, in which the bird’s bill is adapted for the collection of nectar. The bill evolved so that it could reach the nectar at the bottom of a flower’s long tubular corolla. Birds who drink nectar have long, narrow bills and tongues with finely divided tips that form a brush. The tongues are very long, and the edges roll inwards to make a narrow scoop, so the bird can sort of lap up nectar, taking several licks every second. The tongue holds the nectar by capillary action a physical force that causes fluids to rise in narrow tubes. The tongue moves in and out rapidly, carrying nectar up tiny grooves in the tongue, all the way to the mouth.

Hummingbirds can stick their long tongues out far beyond the tips of their bills. This enables them to reach the nectar at the base of flowers. But along with drinking nectar, hummingbirds will also grab any insect they meet. As they flit from flower to flower, they consume the flower’s nectar as well as insects and spiders that provide them with protein.

Birds that eat insects collect their food in a number of ways. The warblers have short, slender, tweezerlike bills, that they sort of use like tweezers to pick small insects off leaves and twigs. Plovers pluck insects from the soil with their short bills. Starlings have longer bills, which they push into the earth and force open to make a hole, and then look down the hole for insects.

The insect eater’s tongue like the bill is specialized to the bird’s diet. The tongue of some woodpeckers is long, sticky, and barbed, which makes it easier for the bird to catch its insect prey. Several species of woodpeckers use their bills as wedges to pry the bark off trees to reach the insects underneath and then lap them up with their long, sticky tongues.


Questions 29 through 34.

Listen to part of a talk in a chemistry class.

Chemistry is sometimes called the central science. This isn’t surprising, since most of the processes going on around us involve chemical changes. Here are just a few of them:

A plant grows by changing simple substances into more complex substances.

The steel in a car rusts. Eggs, sugar, flour, and baking powder are mixed and baked into a cake. Emissions from a power plant cause the formation of acid rain.

Chemistry is the science that deals with the materials of the universe and the changes these materials go through. Chemistry is at the heart of our efforts to create new materials to make our lives better for example, to produce new sources of energy. Chemists work on a lot of different things. Some examine the fundamental particles of matter. Others are looking for molecules in space. Still others are looking for ways to control the diseases that threaten our food supply or us.

But whatever the work, all chemists need certain skills. When my former students come back to visit me, they all say the same thing. They say that what’s essential in their success is an understanding of the fundamentals, the ability to solve problems, and the ability to communicate.

Some people think education is just storing information in the brain. A lot of students just want to memorize lists of facts and then sort of spit it all out on tests. Of course, storing facts in the brain is important. The language of chemistry is unfamiliar at first, and you do have to memorize a lot of terms and definitions. You have to learn the vocabulary before you can communicate. Memorizing facts is important, but it’s just the beginning of education. Don’t stop there. Don’t be afraid to do some thinking of your own, and don’t be afraid to trust yourself to figure things out. Analytical thinking is the center of education. Chemistry courses have a reputation for being difficult. This isn’t surprising, since chemical systems are, well, complicated. Don’t expect to understand everything right away. Just remember that even experienced chemists don’t understand everything at first. It’s not a disaster to make a mistake, but it could be, if you don’t learn from your mistake.

To solve a typical chemistry problem, you have to go through the given information and decide what information is really important. If you can’t do one of the homework problems, don’t just look up the answer in the back of the book. That’s not how you learn. You’ll learn more if you go back and review the relevant material, and then try the problem again. Don’t be afraid to struggle with it. If you do struggle with the problems, then find a classmate to work with, and struggle together. Actually, this is kind of a good way to learn about how scientists work together, trying one thing and then another until they come up with a solution.

It takes time to learn chemistry. You might not understand everything at first, and you might not be able to do the problems the first time you try. You might feel frustrated when you make a mistake. Just keep working and learning from your mistakes and you’ll make steady progress.