A lecture from a science class

Do you like our tests? Check out our shop!

TOEFL Test 3 (PDF+MP3) is waiting for you!

Listen to audio recording and answer the questions.

Listen to part of a lecture from a science class.

Prof: Many people, including scientists, are confused about the distinction between nuts and seeds. Some dictionaries say a nut is also a seed, others say a nut is a fruit, and still others say a nut can be both a fruit and a seed. How can an average person tell the difference? Well, in a nutshell, nuts are seeds but seeds cannot be nuts. Clear as a bell, right?

Part of the confusion stems from the fact that seeds and nuts are classified differently for botanical purposes and culinary ones. Botanists -- that is, scientists who study plants -- define a seed as part of the, er, a flowering plant or tree that will grow into a new plant or tree if it's, uh, buried in the ground and germinated. In this respect it's similar to a human egg, which becomes an embryo when fertilized by sperm. Sometimes the plant embryo becomes enclosed in a covering, called an integument: I-N-T-E-G-U-M-E-N-T. The embryo plus its integument, therefore, constitute a seed. Um, sunflower seeds are good examples of this. You've got to crack open the black outer part, the integument, to eat the white embryo inside, right? That's why we call them sunflower seeds, and not sunflower nuts.

However, it's possible for an embryo to have no type of integument at all. As these embryos grow, the tissue surrounding them develops into a fruit. We see this form in many berries, as well as tomatoes, and in peanuts and beans. So an embryo, or seed, doesn't need a covering to be called a fruit. Now, some plants produce a type of fruit called nuts. A nut is a plant fruit containing a single seed (with or without integument) that does not attach itself to the ovary, or, uh, inside wall of the nut. Nuts have a dry, tough outer shell that doesn't crack open when the seed becomes mature. Acorns, chestnuts, and walnuts are good examples of nuts. In the botanical sense, a nut is a seed because it is a compound ovary; it contains both the seed and the fruit of a plant. Oft [false start] Usually, a plant's seed can be separated from its fruit, like when you poke seeds from a watermelon. But with nuts, the part inside the outer shell contains both the seed and the fruit, and these can't be pulled apart.

This inside part of the nut, the part inside the outer shell, is called a kernel. The kernel is definitely not a nut. It's a fruit. People often eat the kernel, and when they do this, they say that they are eating a nut -- for example, "I'm eating a pecan," or "I'm eating a chestnut." What they should be saying, technically, is "I'm eating pecan meat," or "I'm eating a chestnut kernel." In the same sense, a peanut typically refers to the entire package of seed-slash-fruit encased in its outer shell, as well as to the edible inner seed-slash-fruit. So, while a nut is botanically classified as a seed, it is primarily in this culinary sense that people confuse nuts and seeds.

Because a nut in cuisine is more, uh, loosely defined than a nut in botany, the term "nut" gets slapped on many seeds that are not true nuts. Almonds, for example, are mistakenly called nuts, even though they are actually the edible seeds of plants called drupes, as are coconuts and pistachio nuts. Cashews are another example of nuts that are really seeds, along with Brazil nuts, which are seeds that come from capsules. In culinary language, any kernel used in cooking that is found within a shell may be labeled as a nut. One attribute nuts and seeds have in common is that both are highly nutritious. Nuts are a great source of energy because they have lots of oil, and are also an excellent source of protein, fiber, magnesium and zinc. Additionally, recent [false start] recent studies have also shown they are beneficial for the blood and heart. Many seeds are packed with vitamin E, which is touted for its anti-aging properties. Nuts and seeds are good not only for humans, but also for wildlife, a fact confirmed each fall when animals such as squirrels, chipmunks and jays can be seen busily storing nuts to avoid starvation in the coming winter cold.


What is the lecture mainly about?


According to the professor, how do botanists define a seed?

Listen again to part of the passage and answer the following question.


What does the professor mean when he says this: "Clear as a bell, right?"


Why does the professor mention kernels?


What is true of both nuts and seeds?


Do you like our tests? Check out our shop!

TOEFL Test 3 (PDF+MP3) is waiting for you!