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An extinction event (also known as a mass extinction

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conquistador Master | Next Rank: 500 Posts
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An extinction event (also known as a mass extinction

Post Mon Mar 21, 2016 9:14 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    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.

    Q3: 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.

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    Post Wed Mar 23, 2016 8:59 am
    Mechmeera wrote:
    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.

    Q3: 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.
    Here's what we're told about the Phanerozoic era: Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose

    We know that when a mass extinction happens, extinction rates are relatively high. Well, if they were low before large complex organisms arose, and they were high in the Phanerozoic era, it stands to reason that large complex organisms had to have existed during the Phanerozoic era. So the answer is D

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    NandishSS Master | Next Rank: 500 Posts Default Avatar
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    Post Tue Oct 10, 2017 8:25 pm
    DavidG@VeritasPrep wrote:
    Mechmeera wrote:
    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.

    Q3: 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.
    Here's what we're told about the Phanerozoic era: Mass extinctions seem to be a Phanerozoic-era phenomenon, with extinction rates low before large complex organisms arose

    We know that when a mass extinction happens, extinction rates are relatively high. Well, if they were low before large complex organisms arose, and they were high in the Phanerozoic era, it stands to reason that large complex organisms had to have existed during the Phanerozoic era. So the answer is D
    HI Dave,

    Could you please explain my below query!!!

    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.

    OA: D

    How to find out author would most probably agree with which of the following statements. I often get this kind of question wrong!!!

    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.

    OA: C

    This is very generic question . Do we need to sum up all three para?

    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.

    OA: D

    How B is wrong? Historical occurrence doesn't mean that the author should give series of events?

    Thanks
    Nandish

    Post Wed Oct 11, 2017 5:34 am
    Quote:
    Could you please explain my below query!!!

    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.

    OA: D

    How to find out author would most probably agree with which of the following statements. I often get this kind of question wrong!!!
    There will always be textual evidence to support the correct answer for this kind of question. In the first sentence of paragraph 2, we see this clause: extinction occurs at a very uneven rate. This notion is best encapsulated in D.

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    Post Wed Oct 11, 2017 5:39 am
    Quote:
    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.

    OA: C

    This is very generic question . Do we need to sum up all three para?
    The correct answer doesn't have to capture the gist of the entire passage. Rather, it's best to simply go through the answer choices one by one and find one that has textual support somewhere. In the last paragraph we could these two sentences:

    1) Since life began on Earth, the five major mass extinctions have significantly exceeded the background extinction rate for animal and plant species.
    and
    2) In the past 540 million years, during each of these five major events, over 50% of animal and plant species died.

    If the background extinction rate is far lower than the extinction rate during a major event, and during a major event over 50% of animal and plant species die, it stands to reason that the background extinction rate is far below that 50% threshold. The answer is C

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    Post Wed Oct 11, 2017 5:44 am
    Quote:
    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.

    OA: D

    How B is wrong? Historical occurrence doesn't mean that the author should give series of events?
    B is wrong because the passage isn't about what's causing the extinctions. (No mentioned of meteorites or climate change, etc.) Rather, it's about how the rate of extinction changes over time and spikes during major events.

    'Historical occurrence' simply refers to something that happened in the past.

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    Post Wed Oct 11, 2017 7:19 pm
    Thanks a lot Dave Very Happy

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