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Difference Between Facultative and Obligate

Main Difference

The main difference between Facultative and Obligate is that the Facultative organisms can obtain energy from any three methods of respiration that are aerobic respiration, anaerobic respiration, and fermentation, whereas Obligate organisms can get energy from only one process of respiration that is aerobic respiration, anaerobic respiration, or fermentation.

Facultative vs. Obligate

A facultative organism can live in more than one particular habitats, while the obligate organism can live only in one specific environment. Facultative organisms can obtain energy from any three methods of respiration that are aerobic respiration, anaerobic respiration, and fermentation, whereas obligate organisms can get energy from only one way of respiration that is aerobic respiration, anaerobic respiration, or fermentation. The efficiency of energy production in facultative is high, whereas the energy production in obligate is low.

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Facultative organism includes only one type that is known as facultative anaerobes, while obligate organism consists of two types that are identified as obligate aerobes and obligate anaerobes. Facultative organisms can live with or without the excess of oxygen; on the other side, obligate organisms cannot live without the excess of oxygen. All the facultative organisms can survive in both the external and internal environments of the host; on the other hand, obligate anaerobes can live only inside the host and obligate aerobes to live outside the host in the external environment.

Facultative parasites spend their half-life as a parasite and half as an independent, whereas obligate parasite spends their whole life as a parasite. A facultative parasite can live without the host; on the other side of the coin, obligate parasites cannot live without the host. Facultative organisms are mainly present throughout the liquid medium but almost near the surface, while obligate anaerobes are present at the bottom of the liquid medium, and obligate aerobes are present near the surface of the liquid medium.

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Comparison Chart

FacultativeObligate
Facultative organisms can obtain energy from any three methods of respiration that are aerobic respiration, anaerobic respiration, and fermentationObligate organisms can get energy from only one process of respiration that is aerobic respiration, anaerobic respiration, or fermentation
Condition
It can live in more than one specific conditionsIt can live only a particular condition
Types
It includes only one type that is facultative anaerobesIt consists of two types that are known as obligate aerobes and obligate anaerobes
Importance of Oxygen
It can live in the presence or absence of oxygenIt cannot live in the lack of oxygen
Habitat
It can live inside and outside of the hostObligate anaerobes can live only inside the host, and obligate aerobes live outside the host
Parasites
Facultative parasites can live without the hostObligate parasites cannot live without the host
In a Liquid Medium
It is present throughout the medium but mostly near the surfaceObligate aerobes are found near the surface of a liquid medium, and obligate anaerobes are found at the bottom of the liquid medium
The Efficiency of Energy Production
It has high energy production efficiencyIt has low energy production efficiency
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What is Facultative?

Facultative organisms are organisms that can produce their energy. It can live without the oxygen, but if the oxygen is present in the medium, then it can utilize it. Facultative organisms can live in more than one specific condition. It can produce its energy by any of the three methods, such as aerobic respiration, anaerobic respiration, and fermentation.

It can also live without the host and can spend most of its life as independently. Facultative organisms contain only a single type known as facultative anaerobes. Facultative anaerobes are found near the surface of the liquid medium. It includes facultative fungi, facultative bacteria, and facultative protozoans.

What is Obligate?

Obligate organisms are organisms that cannot produce their energy. That’s why its energy production efficiency is very low. It also cannot survive in the absence of an excess of oxygen. The obligate parasite can live only in specific conditions. It can produce its energy only by one of the three methods, such as aerobic respiration, anaerobic respiration, and fermentation.

Obligate organisms include two types that are obligate aerobes and obligate anaerobes. Obligate aerobes can live only inside the host, and obligate anaerobes can live outside the host. It spends all of its life as a parasite. Obligate aerobes are found at the surface of the liquid medium, whereas obligate anaerobes are found at the bottom of the liquid medium. It includes obligate fungi, obligate bacteria, obligate protozoa.

Key Differences

  1. The facultative parasite can live independently in half of its life; on the other hand, the obligate parasite cannot live as independently.
  2. The facultative parasite can live without the host, while obligate cannot live without a host.
  3. Facultative organisms can survive in more than one specific condition; on the opposite side; the obligate parasite can survive in a particular situation.
  4. The efficiency of energy production is very high in the facultative organism, whereas the ability of energy production is deficient in the obligate parasite.
  5. The facultative organism can survive in the absence of oxygen; on the other hand, the obligate organism cannot survive in the lack of oxygen.
  6. Facultative organisms can live inside or outside the host; on the flip side, obligate organisms can live only in the host.
  7. Facultative organisms include the only single type that is facultative anaerobes; on the other side of the coin, obligate organisms include two types that are obligate aerobes and obligate anaerobes.
  8. Facultative organisms can obtain energy from any three methods of respiration that are aerobic respiration, anaerobic respiration, and fermentation, whereas obligate organisms can get energy from only one process of respiration that is aerobic respiration, anaerobic respiration, or fermentation.
  9. Facultative organisms are found throughout the liquid medium but mostly near the surface of the medium; on the other hand, obligate aerobes are found near the surface, whereas obligate anaerobes are found at the bottom of the liquid medium.

Conclusion

The above discussion concludes the main difference between the facultative and obligate organisms is the type of cellular respiration occur in them. Facultative organisms have only one type known as facultative anaerobes; on the other hand, obligate organisms have two types known as obligate aerobes and anaerobes.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White