EXPLANATION of the PASSAGE

Let's dive into a passage to explain the main idea.
Notice how, in this passage, we do have TWO questions related to the main idea of the passage. Particularly, the first one is tricky






#1 paragraph

The deep sea typically has a sparse fauna dominated by tiny worms and crustaceans, with an even sparser distribution of larger animals.

The fauna = animals that are located in the deep of the oceans, or seas are sparse. That means we do not have a high concentration of animals per square inch or miles. Large animals are even more sparse or rare, which means that the attention is even lower.

However, near hydrothermal vents, areas of the ocean where warm water emerges from subterranean sources, live remarkable densities of huge clams, blind crabs, and fish.

However= but= here we do have a shift. Near certain specific zone such as the vents where the water is warmer than other places, we do NOT have a sparse fauna. Instead, we do have a high concentration of animals: fish, clams, and so on. whatever, just details. But the key concept is the following. we DO NOT have sparse fauna, as in general, we do have in the deep sea.


#2 paragraph


Most deep-sea faunas rely for food on particulate matter ultimately derived from photosynthesis, falling from above.

This fauna in the deep sea takes the food from microscope elements falling from above. From above means from the ocean's surface, these elements fell to the deep sea. From up to down. This is the only thing you should keep in mind and this is also important.

The food supplies necessary to sustain the large vent communities, however, must be many times the ordinary fallout.

Here we do have a pivotal concept: because the community in the vents area is huge, then the elements that come from above are not sufficient. Therefore, these animals must have another source for their food

The first reports describing vent faunas proposed two possible sources of nutrition: bacterial chemosynthesis, production of food by bacteria using energy derived from chemical changes, and advection, the drifting of food materials from surrounding regions.

We do have two main reasons that could explain how the fauna in the vents area take the food
1) production of food by bacteria using energy
2) advection, the drifting of food materials from surrounding regions. The food comes from the surrounding areas the vents

Later, evidence in support of the idea of intense local chemosynthesis was accumulated: hydrogen sulfide was found in vent water; many vent-site bacteria were found to be capable of chemosynthesis; and extremely large concentrations of bacteria were found in samples of vent water thought to be pure.

Just keep in mind that here we do have an explanation of the reason 1) above. Just keep in mind this. No need to delve into the details. If you will need of it , you will know where the chemosynthesis process is located

This final observation seemed decisive. If such astonishing concentrations of bacteria were typical of vent outflow, then food within the vent would dwarf any contribution from advection.

this sentence tells us essentially one thing: if the hypothesis is true, then chemosynthesis is the main reason how the fauna take food. chemosynthesis > advection

Hence, the widely quoted conclusion was reached that bacterial chemosynthesis provides the foundation for hydrothermal - vent food chains - an exciting prospect because no other communities on Earth are independent of photosynthesis.

Hyphotesis 1) seems the most reasonable


There are, however, certain difficulties with this interpretation. For example, some of the large sedentary organisms associated with vents are also found at ordinary deep-sea temperatures many meters from the nearest hydrothermal sources. This suggests that bacterial chemosynthesis is not a sufficient source of nutrition for these creatures.

Here, we do have a significant shift: because large animals are also found in other locations suggests that the phenomenon described at point 1) is NOT the only possible source of food.


Another difficulty is that similarly dense populations of large deep-sea animals have been found in the proximity of "smokers" - vents where water emerges at temperatures up to 350° C. No bacteria can survive such heat, and no bacteria were found there Unless smokers are consistently located near more hospitable warm-water vents, chemosynthesis can account for only a fraction of the vent faunas.

Here we do have an important fact: large animals that should rely on for food in chemosynthesis, which in turn out uses bacteria, are located in the proximity of areas where the temperature is too high and the bacteria cannot survive. Therefore, these same bacteria cannot produce the food. UNLESS the same vants are located in more mild waters.

It is conceivable, however, that these large, sedentary organisms do in fact feed on bacteria that grow in warm-water vents, rise in the vent water, and then rain in peripheral areas to nourish animals living some distance from the warm-water vents.

A possible solution to this paradox is that these large animals feed on bacteria that reproduce in mild vents and then these bacteria reach those areas to feed the animal a bit far aways those vents areas where the bacteria create the food. Mhhhh a complicated story, though.


#3 paragraph

Nonetheless, advection is a more likely alternative food source. Research has demonstrated that advective flow, which originates near the surface of the ocean where suspended particulate matter accumulates, transports some of that matter and water to the vents.

Notice the word nonetheless in the explanation for the fact # 1). That means we do not have a definitive conclusion or understanding of this phenomenon.
Advection is a possible alternative to food production

Estimates suggest that for every cubic meter of vent discharge, 350 milligrams of particulate organic material would be advected into the vent area. Thus, for an average-sized vent, advection could provide more than 30 kilograms of potential food per day. In addition, it is likely that small live animals in the advected water might be killed or stunned by thermal and/or chemical shock thereby contributing to the food supply of vents.

Here is just how advection works. Just an explanation of the possible process.



EXPLANATION of the QUESTIONS


#1 QUESTION

When you need to find the overall idea that the passage conveys you must read in brief the key elements of the passage itself. Actually, there is not a bullet-proof strategy because the answer arose from the sense and feeling you do have from it. Of course, there is a logic in answering it. However, these kinds of questions are NOT based on pure logic but rather common sense

Answer this question in 30 seconds is possible

Look at these key parts



two crucial elements here: however which is a shift in the argument and put you in the path that the passage talks about something else of that which is apparent and areas, which implies locations










The passage provides information for answering which of the following questions?

(A) What causes warm-water vents to form?

In the above quotation NO sign of warm water is the key element but rather the vent

(B) Do vent faunas consume more than do deep-sea faunas of similar size?

the consumption is NOT the key element

(C) Do bacteria live in the vent water of smokers?

The key element is the vent which is basically a location, an area for food and blah blah blah.....CORRECT

(D) What role does hydrogen sulfide play in chemosynthesis?

Hydrogen is NOT a key element of what we are talking about. Notice how this is tricky because the passage talks about hydrothermal vents NOT hydrogen

(E) What accounts for the locations of deep-sea smokers?

The passage talks about the proximity of deep-sea animals to smokers areas which are still VENT areas.

From all above as you can see if you are able to use this strategy even the most complex passages can be addressed in 30 seconds. However, this implies that your level of standard English is pretty decent



#2 QUESTION


The primary purpose of the passage is to

Explanation

A study of the passage reveals that it is trying to explain the food source for the dense populations for small and large animals near hydrothermal vents. Initially, the conclusion was reached that bacterial chemosynthesis provides the foundation for hydrothermal - vent food chains - on the basis of some evidence. Later evidence pointed towards advection as a more likely food source.

(A) describe a previously unknown natural phenomenon. Wrong.
(B) reconstruct the evolution of a natural phenomenon. Wrong.
(C) establish unequivocally the accuracy of a hypothesis. Wrong.
(D) survey explanations for a natural phenomenon and determine which is best supported by evidence. Correct.
(E) entertain criticism of the author's research and provide an effective response. Wrong.