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Related Concept Videos

Rules for Significant Figures01:44

Rules for Significant Figures

41.5K
In any measurement, the precision of the measuring tool is an essential factor. An ordinary ruler, for example, can measure length to the closest millimeter; a caliper, on the other hand, can measure length to the nearest 0.01 mm. As a result, the caliper is a more precise measurement tool because it can measure extremely minute changes in length. The measurements will be more accurate if the measuring tool is more precise.
It should be emphasized that when we represent measured values, the...
41.5K
Uncertainty in Measurement: Significant Figures03:34

Uncertainty in Measurement: Significant Figures

86.4K
All the digits in a measurement, including the uncertain last digit, are called significant figures or significant digits. Note that zero may be a measured value; for example, if a scale that shows weight to the nearest pound reads “140,” then the 1 (hundreds), 4 (tens), and 0 (ones) are all significant (measured) values.
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Orders of Magnitude01:15

Orders of Magnitude

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The order of magnitude of a number is the power of 10 that most closely approximates it. Thus, the order of magnitude estimates the scale (or size) of its value. To find the order of magnitude of a number, take the base-10 logarithm of the number and round it to the nearest integer. Then the order of magnitude of the number is simply the resulting power of 10.
The order of magnitude is simply a way of rounding numbers consistently to the nearest power of 10. This makes doing rough mental math...
27.9K
Numerical Calculations01:24

Numerical Calculations

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In engineering applications, the representation of the numerical value is critical. Presenting or reporting the answer is one of the essential parts of engineering practices. Numerical calculations are performed using handheld calculators or computers since numerically accurate answers are always preferred.
The solution to a problem is obtained using different methods. While manually solving algebraic symbols is one of the most common methods, the graphical method is often preferred. Computers...
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International System of Units01:29

International System of Units

5.5K
The International System of Units, known as the SI system, is a universally accepted measurement system recognized and used worldwide. The SI system is based on a set of three base units considered absolute, and their values do not change with location. These base units are meters, kilograms, and seconds.
Prefixes are used to define both larger and smaller quantities in the SI system. For example, milli, micro, and nano define smaller quantities, while kilo, mega, and giga are used to define...
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Significant Figures in Calculations00:58

Significant Figures in Calculations

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Uncertainty in measurements can be avoided by reporting the results of a calculation with the correct number of significant figures. This can be determined by the following rules for rounding numbers:
20.6K

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Predicting the Effectiveness of Population Replacement Strategy Using Mathematical Modeling
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After All, Only Millions?

Rudolf Amann1, Ramon Rosselló-Móra2

  • 1Max Planck Institute for Marine Microbiology, Bremen, Germany ramann@mpi-bremen.de.

Mbio
|July 7, 2016
PubMed
Summary

Despite extensive sequencing, the census of microbial species is nearing saturation. Current data suggest Earth may host millions, not trillions, of bacterial and archaeal species.

Area of Science:

  • Microbiology
  • Genomics
  • Bioinformatics

Background:

  • Recent studies indicate PCR-based retrieval of 16S rRNA genes is approaching saturation.
  • Sequencing efforts have vastly increased, yet new species discovery is slowing.

Purpose of the Study:

  • To update the census of Archaea and Bacteria species.
  • To evaluate the current coverage of microbial diversity through gene sequencing.

Main Methods:

  • Analysis of 16S rRNA gene sequences from public databases.
  • Application of rarefaction analysis to estimate diversity coverage.

Main Results:

  • Approximately 95% of analyzed 16S rRNA genes are identical to existing database entries.
  • Rarefaction analysis suggests only one-third of bacterial and archaeal diversity has been covered.

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  • The total number of microbial species may be in the millions, not the previously estimated trillions.

    • Conclusions:

    • The census of Archaea and Bacteria is approaching saturation despite ongoing sequencing.
    • Current methods may have overestimated the total number of microbial species on Earth.