PASSAGE 3 – Questions 21-30
Symbiosis is a close ecological relationship between two dissimilar organisms. They assist each other with feeding, defending, and reproducing. In symbiosis, at least one of the pair benefits from the relationship. The other may be injured (parasitism), unaltered (commensalism), or may also benefit (mutualism).
An interesting mutually dependent relationship exists between the pine and the pinon jay. Blue pinon jays settle on the tops of pine trees and pick at the dark round seeds from the sticky cones. They store the seeds in their throats, fly off and hide them somewhere, and then return to repeat the process again. It seems the reproductive cycle of a pine jay corresponds with the ripening of the pine's seed. Similarly, the pine is dependent on the pinon jays for distribution of the seeds.
Seeds are stored in the bark of a tree or in the ground. Using their long bills, pinon jays plant and store them for later consumption. Their throats can expand to hold a large number of seeds; one pinon jay has been reported carrying 50 seeds in one trip. After they have planted the seeds, they return to eat them. Using their bills like a woodpecker, they hammer the seed until the shell breaks. Any unrecovered nuts are then grown into new trees. This fascinating relationship has been ongoing for thousands of years.
When both species benefit each other, this is called mutualism. An example of mutualism is a plant and fungi. The fungus occupies the cortex cells of the secondary roots of the plant. This relationship is called a ‘mycorrhiza.’ It helps the plant absorb inorganic nitrogen and phosphorus from the soil. Some fungi also produce antibiotics which may prevent the invasion of parasitic fungi and bacteria. Another example of mutualism is pollination. Bees carry pollen from one plant to the next when they seek out plants for nectar. They feed themselves on the nectar, and the plants reproduce after fertilization by the pollen from other plants.
Mutualism can also bring together two very different organisms, for example, a buffalo and an ox bird. These birds journey on the backs of African buffalo eating their parasites. The bird receives food, and the buffalo is rid of irritating insects. There are also a number of fish that provide an excellent example of mutualism. Known as ‘cleaner fish,’ these fish get rid of parasites and dead skin found on other fish. The best-known example is the ‘cleaner wrasse,’ which dwells in the Pacific and Indian oceans. They clean large predatory fish by eating tissue and parasites off their skin. This relationship provides food and protection for the wrasse and several health benefits for the other fish.
The other two types of symbiosis, besides mutualism, are commensalism and parasitism. [A] Commensalism refers to a symbiotic relationship where one organism eats the unused food of another. [B] One benefits, but the other is not affected. Examples include the remora and the shark. The remora attaches itself to the shark, when the shark feeds itself, the remora picks up scraps. [C] One example of commensalism in humans is bacteria living in our intestines that feed on food in our gut. [D]
In parasitism, one organism benefits and the other is harmed. Parasites live off the body of other organisms and receive nourishment from their tissues, while also inflicting damage on their hosts. Plants are parasitized by bacteria, fungi, and a handful of other plants. Parasites cause harm by entering the tissue of the host for their own nutritional benefit.
None of these relationships are fixed, and it is likely that what starts as a parasitic relationship may gradually evolve into a mutualistic one. For example, in 1966, amebas were discovered that had become infected with bacteria. However, after five years, it was found that the core of the amebas had become dependent on the bacteria; thus, parasitism had evolved into mutualism. Unfortunately, the inverse is also possible; mutualistic associations may evolve into parasitic ones.
According to paragraph 2, what does the pinon jay do for the pine tree?
- A. It gives the tree important nutrition.
- B. It provides a primary means of seed dissemination for pinon trees.
- C. It keeps the tree free from parasites.
- D. It helps the tree produce larger seeds.
- A. matches
- B. includes
- C. exposes
- D. protects
- A. By holding up to 50 in its mouth
- B. By burying them in the ground
- C. By protecting them in its nest
- D. by allowing them to develop into new trees
- A. bacteria
- B. mutualism
- C. mycorrhiza
- D. fungus
- A. An animal eating parasites from another
- B. An animal licking the body of another
- C. An animal providing protection for another
- D. An animal keeping another awake and alert
- A. explain the details behind a mutualist association
- B. demonstrate a connection between an active parasite picker and host
- C. show how one animal can benefit from the acts of another
- D. give an example of one animal causing the suffering of, another
- A. There are many types of creatures that are very well developed and have the strength to support other species.
- B. Sometimes, the organisms supplying parasites are very harmful to their hosts.
- C. Some animals are selfish and only cause damage to their hosts.
- D. Organisms which must depend on others die easily because they are not strong.
- A. slowly
- B. increasingly
- C. constantly
- D. rapidly
- A. A plant and its fungi
- B. Pollen transfer from one plant to another
- C. The remora and the shark
- D. A buffalo and an ox bird
- A. [A]
- B. [B]
- C. [C]
- D. [D]
PASSAGE 4 – Questions 21-40
Earth has several distinct layers; the outermost of these is the crust, which has an inconsistent thickness of 35-70 km in the continents and 5-10 km in the ocean basins. The second layer is known as the mantle, which is about 2900 km thick, and divided into an upper and lower mantle. Most of Earth's internal heat is situated here. The upper mantle has an area known as the low-velocity zone, where secondary waves decrease rapidly and then gradually increase. The last layer is the core. This is a thick ball of iron and nickel divided into two layers, the inner core and the outer core.
The inner core is solid, whereas the outer core is so hot that the metal is always molten. However, because the force at the inner core is so immense, it cannot melt. Due to Earth's rotation, the outer core spins around the inner core, which causes the Earth's magnetism. The inner core consists of iron, nickel and other elements, probably a mix of carbon, oxygen, sulphur, silicon, and potassium. The temperature is extremely high, and due to pressure, the core is solid. Because the outer core is liquid, mainly consisting of iron, nickel and about 10% oxygen and sulphur, here the temperature is not as high.
Both the outer and inner cores together create the Earth's magnetism. The core has a huge influence on Earth. Because it is so hot, it radiates a natural heat to the upper layers, setting off a current of heat, which in turn causes the movement of the tectonic plates. Because of Earth's rotation, the outer core spins, but the inner core does not because it's solid. This provides a sort of dynamo effect and causes the Earth's magnetic force.
A seismic wave is a wave that travels through Earth; it is often the result of a tectonic earthquake. There are two kinds of seismic waves, “body waves” and “surface waves.” Other waves do exist, but are of little importance. Body waves travel through the center of Earth, following ray paths which are bent by the unstable density and stiffness of Earth's interior. These differ according to temperature, phase, and structure. Body waves send out the first tremors of an earthquake as well as any later ones.
There are two kinds of body waves, “primary” and “secondary” waves. Primary waves are compression waves, meaning the ground is alternately compressed and expanded in the direction of propagation. These waves can travel slightly faster through solids than secondary waves can, and are also able to travel through any type of material. Through air, they take the form of sound waves and so travel at the speed of sound.
Primary waves, when created by an earthquake, are less destructive than sound waves due to their minor amplitudes. Secondary waves are tilted waves; in other words, the ground is shifted vertically in the direction of transmission. Here, the ground moves from one side to the other. Secondary waves are only able to travel through solids, not liquids or gases, and thus are unable to travel through Earth's core. Primary waves are faster than secondary waves. Primary and secondary waves are usually produced by earthquakes and volcanoes. However, they can also be produced by people using explosives or large machinery.
Surface waves are comparable to water waves traveling just under Earth's surface. They travel at slower speeds than body waves. Surface waves can be the most devastating type of seismic wave due to their low frequency, long duration, and large amplitude. In theory, they are understood as a system which relates to primary and secondary waves.
[A] The moment an earthquake occurs, seismographs try to record its primary and secondary waves, but often they cannot detect the secondary waves of a distant earthquake. [B] This may be due to the fact that secondary waves are unable to pass through liquids. [C] This information about wave travel helps scientists determine the internal structure of the planet. [D]
In paragraph 1, what does the author say about the presence of the low-velocity zone in the Earth's interior?
- A. It causes the high-frequency stimulation.
- B. Its width is consistent with the fault zone.
- C. It induces regionally extensive oscillations.
- D. It is located just above the lower crustal boundary.
- A. compressed
- B. dilated
- C. immeasurable
- D. varied
- A. It contributes to the Earth's magnetic field.
- B. It is always molten and liquid.
- C. It is under a lot of pressure.
- D. It mainly consists of iron, nickel and some lighter elements.
- A. The convection of heat from the core
- B. The gravitational effect of the core
- C. The powerful magnetic forces of the core
- D. The spinning of the inner and outer core together
- A. To show that primary waves are far more powerful than secondary waves
- B. To demonstrate the effect of seismic waves on the Earth
- C. To develop understanding of the structure of the Earth's interior
- D. To explain that scientific detection methods are very efficient
- A. change
- B. period
- C. heat
- D. construction
- A. faint
- B. destructive
- C. productive
- D. quiet
- A. Although primary and secondary waves would be recorded, the secondary waves are not strong enough to be detected at a distance.
- B. Seismic waves are too small to be felt as a noticeable earthquake, but detectable by seismographs.
- C. Secondary waves can be generated as a result of nonlinear interaction, so seismographs cannot detect them.
- D. Because of extensive fault repetition, the primary wave is the most powerful force in an earthquake.
- A. Volcanoes would not exist if earthquakes never happened.
- B. They are caused by the force of primary waves hitting the crust.
- C. They are primarily caused by the heat from the Earth's core.
- D. There is no more destructive thing in the world.
- A. [A]
- B. [B]
- C. [C]
- D. [D]
