An extinction event (also known as a mass extinction or biotic crisis)

Question

An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the amount of life on earth. Such an event is identified by a sharp change in the diversity and abundance of macroscopic life. It occurs when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life.

Over 98% of documented species are now extinct, but extinction occurs at a very uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to land organism fossils.

Since life began on Earth, the five major mass extinctions have significantly exceeded the background extinction rate for animal and plant species. The most recent, the Cretaceous–Paleocene extinction event, which occurred approximately 66 million years ago, was a large-scale mass extinction of animal and plant species in a geologically short period of time. In the past 540 million years, during each of these five major events, over 50% of animal and plant species died. Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose.   1 
 1. It can be inferred from the passage that:

(A) in an extinction event, there is a dramatic decrease in microbial life on earth.
(B) over 90% of easily observed, biologically complex species become extinct during a biotic crisis.
(C) the background extinction rate of animal and plant species is well below 50%.
(D) marine fossils are easier to find and thus more useful to those studying mass extinction events.
(E) new species do not emerge during a mass extinction event.

2 
 2. It can be inferred from the passage that the Phanerozoic era was:

(A) a time period that existed before 540 million years ago.
(B) a time period during which few new species emerged.
(C) a time period before the Cretaceous–Paleocene era.
(D) a time period during which large, complex organisms existed.
(E) a time period during which fewer than 50% of animal and plant species died.

3 
 3. The author would most probably agree with which of the following statements?

(A) The diversity of microbial life has changed dramatically during mass extinction events.
(B) The Cretaceous–Paleocene extinction event was the most significant in the past 540 million years.
(C) There were many mass extinction events prior to 540 million years ago.
(D) Extinction rates have varied widely over the past 540 million years.
(E) Mass extinctions are less likely now than in the past 540 million years.

4 
 (4) The primary purpose of the passage is to:

(A) warn readers about the possible dangers of mass extinction events.
(B) discuss the causes of a particular scientific phenomenon.
(C) present new evidence to support the theory of mass extinction events.
(D) describe an important scientific and historical occurrence
(E) suggest that mass extinctions are likely to continue in the future.

sayantanc2k · Accepted Answer

Your misunderstanding of the last line of the passage seems to be a result of not being able to inerpret the function of the modifier "with extinction rates low before large complex organisms arose" properly. This modifier does not refer to "Phanerozoic-era phenomenon", but the entire previous clause. Shift the modifier at the beginning, and then probably the meaning would be clear:

With extinction rates low before large complex organisms arose, mass extinctions seem to be a Phanerozoic-era phenomenon.

The above sentence implies that extinction rates were low before large complex organisms arose. This also implies that mass extinctions were possible only AFTER large complex organisms arose. Since mass extinctions occured during the Phanerozoic-era, it can be inferred that there were large complex organisms during this era. Hence D is the correct option.

Nevernevergiveup · Answer

An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the amount of life on earth. Such an event is identified by a sharp change in the diversity and abundance of macroscopic life. It occurs when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life.

Over 98% of documented species are now extinct, but extinction occurs at a very uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to land organism fossils.

Since life began on Earth, the five major mass extinctions have significantly exceeded the background extinction rate for animal and plant species. The most recent, the Cretaceous–Paleocene extinction event, which occurred approximately 66 million years ago, was a large-scale mass extinction of animal and plant species in a geologically short period of time. In the past 540 million years, during each of these five major events, over 50% of animal and plant species died. Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose.

Q1: It can be  inferred  from the passage that:
a) in an extinction event, there is a dramatic decrease in microbial life on earth................ only macroscopic life can be observed and we have no proper measured info reg microbial life 
b) over 90% of easily observed, biologically complex species become extinct during a biotic crisis........... it is not a norm which happens all the time 
c) the background extinction rate of animal and plant species is well below 50%
d) marine fossils are easier to find and thus more useful to those studying mass extinction events. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic but whether they are easy to find is not known as per the passage. 
e) new species do not emerge during a mass extinction event............. .new info since nowhere it is mentioned about species emerging activity.

Q2 : The author would most probably agree with which of the following statements?
a) The diversity of microbial life has changed dramatically during mass extinction events. only macroscopic life can be observed and we have no proper measured info reg microbial life 
b) The Cretaceous–Paleocene extinction event was the most significant in the past 540 million years.............. recent major event that happenend in short time. We dont know whether it is most significant or not. 
c) There were many mass extinction events prior to 540 million years ago........... Since life began on Earth, and In the past 540 million years, during each of these five major events, does not give any info of mass events before 540 million yrs 
d) Extinction rates have varied widely over the past 540 million years.
e) Mass extinctions are less likely now than in the past 540 million years..........there is no such prediction.

Q4: The primary purpose of the passage is to:

a) warn readers about the possible dangers of mass extinction events........... author did not warn anyone 
b ) discuss the causes of a particular scientific phenomenon............ author did say It occurs when but did not say why  
c) present new evidence to support the theory of mass extinction events....... there is mention of new evidence 
d) describe an important scientific and historical occurrence
e) suggest that mass extinctions are likely to continue in the future........ there is mention of suggestion

thangvietname · Answer

most, if not all gmat passage, are well structured and hard to understand , followed by easy question testing the understanding of the passages. this case is opposite to the case created by prep companies, in which passages are too easy, and not well structured and followed by very hard questions.

gmat test us ability to understand the passages and to infer from information in the passage. I think prep companies' passages test only the inference.

I alway see that the gmat typical passages are harder than the prep companies tests.

KM2018AA · Answer

For the Q-3, can you please explain as to how can we conclude the same about Phanerozoic era?

The passage mentions that Mass Extinctions were Phanerozoic era phenomenon with rates low before large organisms arose. Should not this sentence structure mean that phanero era was the one wherein the extinction rates were low and was the era devoid of large organisms?

broall · Answer

Official Explanations from Veritas:

Question 1:

In this example, as is the case with many hard inference problems, you must link several pieces of information to find the proper inference. Using process of elimination, start with (A). In the first paragraph you learn that mass extinction events are based on the extinctions of easily observed, biologically complex components. You therefore have no idea from this passage how the microbial organisms are affected during a mass extinction event and (A) is incorrect. In the passage you learn that 98% of known species have become extinct but you only learn that over 50% were lost in each of the 5 major mass extinctions. You therefore cannot conclude that over 90% of complex species become extinct during a mass extinction event and (B) is also incorrect. Note: the testmakers are hoping you use the wrong data point to create this improper inference. (C), which is correct, requires that you link together two pieces of information. In the beginning of the 3rd paragraph you learn that “the five major mass extinctions have significantly exceeded the background extinction rate” and then you learn that the rate of those mass extinctions is well over 50%. This allows you to conclude that the background rate is far below 50%. In (D), you learn that marine fossils are used because they provide a better fossil record and stratification but you do not know if they are easier or more difficult to find than other types. In (E), no information is given about whether new species emerge during an extinction event so you cannot make that inference.

Answer is (C).

Question 2:

For this type of question, go find the key word (end of the last paragraph) and make the proper inference. The sentence reads: “Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose.” In the first part of the sentence you learn that mass extinctions took place during this era. In the second part you learn that the extinction rates were low before “large complex organisms arose” (i.e. before this era.) From this you can conclude definitively that this era was a time during which large, complex organisms existed and (D) is thus correct. (A) must be false from this information, as the Phanerozoic era had to overlap with those 540 million years. For (B), you have no idea from this passage about the emergence of species. Again, (C) is contradicted by this section and for (E) you cannot make this inference (and the passage suggests that number is near 98%).

Answer is (D).

Question 3:

As you learned in several previous questions, you cannot assess the impacts on microbial life from this passage so (A) is incorrect (you have no idea what the author would think). For (B), while the author references this extinction event specifically, no information is given about its significance in relation to the other major extinction events. (C) is contradicted by the passage as you learn at the end of the passage that extinction rates were low before that time period. For (D), there is direct support for this statement in the first sentence of the 2nd paragraph, in which the author states that “extinction occurs at a very uneven rate.” No information is given in the passage to support (E) so it is incorrect. Answer is (D).

Question 4:

For primary purpose questions, you should focus on the scope of the passage and the intent of the author. For (A) the author does not give any specific warnings and the passage is explanatory/descriptive, not opinionated. For (B), the author does not discuss at all what has caused these mass extinction events. He simply discusses what they are and when some have occurred. For (C), the author does not present any new evidence, just discusses what is known about them now. (D) matches the scope and tone perfectly and is thus correct. For (E) there is no discussion about what will occur in the future.

Answer is (D).

Tanujm · Answer

In reference to Q3, the passage says that the Cretaceous–Paleocene extinction event was the most recent mass extinction event. Why can C not be inferred basis this?

coreyander · Answer

VeritasKarishma   SajjadAhmad  I have the same doubt. Can you please clarify Q3, on what basis can C be eliminated?

" The most recent, the Cretaceous–Paleocene extinction event , which occurred approximately 66 million years ago, was a large-scale mass extinction of animal and plant species in a geologically short period of time."

"Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose."

Cretaceous-Paleocene is most recent. Hence, Phanerozoic-era should have occurred before. Hence,  (C) a time period before the Cretaceous-Paleocene era   could be valid.

KarishmaB · Answer

Read these lines very carefully.

Since life began on Earth, the five major mass extinctions have significantly exceeded the background extinction rate for animal and plant species.  - there have been 5 major mass extinctions.

In the past 540 million years, during each of these five major events, over 50% of animal and plant species died.  - These 5 mass extinctions have taken place within the last 540 million years.

Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose.  - Mass extinction is a phenomenon of Phanerozoic-era. Before this there were no large complex organisms and extinction rates were low.

This means the Phanerozoic-era is the 540 million years era in which large complex organisms arose.

Answer (D)

Pranjal3107 · Answer

But doesn't it suggest that the large organisms arose ? How can we infer that they existed ? I got D using elimination. But D really does not seem right as well.

AnirudhaS · Answer

this chart might help to visualise. Red is the inferred data.

On you specific question about how can you infer that they existed..
Well if they did not exist then whose extinction happened in the past 540 million years? We already know this from the passage -  "Such an event is identified by a sharp change in the diversity and abundance of macroscopic life." . So we cannot detect small-simple organism's extinction. So large complex organism must exist for a period of time before they are deemed extinct.

Hope this helps.

VerbalBot · Answer

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An extinction event (also known as a mass extinction or biotic crisis)

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GMAT Reading Comprehension (RC) Questions

An extinction event (also known as a mass extinction or biotic crisis)

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