Exercise
You will hear a series of passages. Click the Exercise link and as you listen, write notes in Exercise 1 that might help you remember the main ideas. Remember to organize them as well as you can based on last week’s note taking lessons.
Listening
Number 1
Transcript
Chocolate is a favorite treat and ingredient used all over the world. It's interesting to learn where chocolate actually originates, but what's even more interesting is the detailed process that is necessary to produce it. Over 3,000 years ago, chocolate began to be produced in an area that stretches from Mexico south into northern South America. It is in these areas that the cacao tree grows. That's cacao, C-A-C-A-O. The seeds or pods that grow on the tree is where we get the ingredients to make chocolate.
Each pod contains cacao beans inside, which by themselves are not really edible due to the fact that they are so bitter. So they have to go through a process that allows the flavor to come out. The beans are removed from the pods and placed in a large pile or bin for several days, where the process of fermentation takes place. During this time, yeast and various bacteria interact with the beans, producing different types of acids, which begin to release a flavor that resembles what we come to know as chocolate.
After fermentation, the beans need to be thoroughly dried in the sun for up to another week. The dried beans are then shipped off to processing areas, where they are further cleaned and sorted before being roasted, much like they do to coffee beans before they're used. The outside of the bean needs to be peeled off and discarded, because it is only the inside part, called the nib, that is used in the next part of production. The nibs are then ground up into a fine powder called cacao liquor, and it is a pure form of chocolate that can be used in a number of applications.
The cacao liquor contains two ingredients, the cacao solids and the cacao butter. By changing the proportion of each of these components and adding other substances, the variety of chocolate can be made. Melting the cacao liquor and forming it into solid pieces creates unsweetened baking chocolate, which is still quite bitter and is generally used in baking and never eaten on its own. To make the sweet, dark chocolate we enjoy so much requires adding other types of fat and sugar. For milk chocolate, not surprisingly, milk products are added. White chocolate, however, is unique in that it actually contains no cacao solids at all, only the fatty cacao butter extracted from the cacao nibs.
Number 2
Transcript
Number two. Ants are one of the most common and easily identifiable types of insects on the planet and they have been here for well over a hundred million years and consist of nearly 12,000 different species. They are social insects and live in colonies, some small with only a dozen members or so and others simply enormous which may contain millions of members. They are so numerous in some places that is estimated they make up 15% or more of all animal biomass, that is the weight of all animals in a given tropical rainforest. Some even believe all the ants in the world would weigh more than every human.
Well let's take a look at some of the different types of ants. Hopefully this will give a good picture of the huge diversity that exists among them. First, leafcutter ants, whose name pretty much describes their primary function. These ants are found in Central and South America and they have developed an advanced system of agriculture where they actually farm their own food. They eat a special fungus like mushrooms that only grows underground under certain conditions. They cut leaves from above ground and carry them back into their underground nests where they lay the leaves next to the fungus which uses the leaves as a food source. The ants even protect the fungus from other insects.
Unlike leafcutter ants, fire ants live in large above-ground mounds which they create and don't grow their food. They eat young plants and various types of seeds. They're originally from South America but have made their way around the world and they get their name from the burning sting they can give. Unlike other ants which may bite and excrete acid in the wound, fire ants bite, hold on, then use a stinger on their abdomen. They will often work together to attack and kill small animals for protection or food.
The last type of ant we'll look at are army ants which are found in two major areas, Central America and Africa. Whereas leafcutters and fire ants construct permanent structures to live in, colonies of army ants are always on the move. They are strictly carnivorous, eating only other animals and no plants, and march for several weeks searching for and killing their food. Each night they find a hidden place where they make a nest out of their own bodies by biting and holding on to each other. In the morning they're off again in search of food. Obviously the term army ant is derived from this behavior.
Number 3
Transcript
One key element of auto mechanics that we have to go over first is the basics of what is actually happening inside the engine of a car or truck. It's hidden and all we usually experience is the power produced by an engine which allows a car to move. So what's going on inside there? Let's look at the function of a four-stroke engine. It's called four-stroke simply because there are four very distinct parts of the process. Intake, compression, power, and exhaust. So first, intake. The air-gas mixture enters the top of the cylinder when the intake valve is in the open position and the exhaust valve is closed. The piston is at the lowest point in the cylinder at this time, allowing the whole cylinder, known as the compression chamber, to fill with the air-gas mixture. During the second stage of the process, compression, both the intake and exhaust valves are in the closed position and the piston, pushed by the connecting rod and crankshaft, moves up the cylinder, effectively compressing the air-gas mixture in preparation for the next stage, which is power. At the top of the cylinder is a spark plug, which, as the name suggests, creates an electric spark just as the air-gas mixture reaches its maximum compression. This spark ignites the gas and creates a small but very powerful explosion, which forces the piston down towards the bottom of the cylinder. The air-gas mixture, which can now no longer be ignited, needs to be removed from the cylinder, which leads to the exhaust part of the cycle. The intake valve is closed and the exhaust valve is open, so as the piston moves up the cylinder, the burned gas is pushed out of the compression chamber. Both valves reverse their state once again at this point, and the piston is ready to move down and draw in a new air-gas mixture and start the process all over again.