- What is binary fission?
- Types of binary fission
- Examples of binary fission
- Other types of asexual reproduction
We explain what binary fission is, its stages, the types that exist and various examples. Also, other forms of asexual reproduction.
What is binary fission?
Bipartition or binary fission is a mechanism of asexual reproduction of the unicellular living beings, typical of prokaryotes, that is, of bacteria and archaea. It consists of the duplication of the DNA cell phone individual, as a previous step to the division of the cytoplasm in two. Thus, it gives rise to two daughter cells with identical genetic material.
This is the most common form of reproduction in the bacterial world. In some species can occur at an impressive rate (a bacterium Escherichia coli can be divided once for every 20 minutes), as long as the conditions of the surrounding environment are suitable.
In addition to the rapid colonization of the environment, this reproductive rhythm has purposes adaptive: with this reproductive rhythm, the rate of mutations it is usually high. This produces new bacterial strains better adapted to the environment (for example, more resistant to antibiotics). In part this is the reason for the great evolutionary success of bacteria, present in absolutely everyone.
Binary fission takes place through a series of stages:
- DNA replicates to create an exact copy of itself.
- Each set of DNA is oriented towards an opposite region of the cell. Cell organelles replicate as well.
- The protein FtsZ is activated, which forms filaments around the axis of division of the cell. These filaments make the membrane grow into the cytoplasm, narrowing the cell.
- A septum (or waist) is formed that gradually narrows until it completely separates the cytoplasm in two, thus forming two identical individuals (daughter cells), but living independently.
Types of binary fission
There are several possible forms of binary fission, depending on how the single-celled organism divides itself:
- Regular. When the cell divides symmetrically.
- Irregular or type amoeba. When the divisions occur in rhizopods ("fingers") or in a disorderly manner.
- Longitudinal. When the cell divides from its horizontal axis.
- Cross.When the cell divides perpendicular to the axis of the cell spindle.
- Oblique When the cell divides longitudinally at first, but then becomes transverse.
Examples of binary fission
There are plenty of examples of this type of reproduction. Most prokaryotic organisms and some eukaryotes they use it. In fact, the fight against bacterial infections is so arduous because its splitting rate is high. Thus, they reproduce by binary fission:
- Bacteria of all kinds and genus, such as the aforementioned Escherichia coli, and arches like the extremity Methanobacterium bryantii.
- Primitive eukaryotes like Crypthecodinium cohnii or the species of paramecium.
- Some protozoa like the amoebaAmoebidae).
Other types of asexual reproduction
The mechanisms of non-sexual reproduction are those that involve a single individual. Therefore, they have little or no genetic variation. In addition to binary fission, these types of reproduction include:
- Gemmation. The progenitor forms extensions or prominences of your body. Eventually, these extensions can separate from him and have a life of their own. In other cases, they stay together and start a colony. When it occurs at the cellular level, it is a mitosis asymmetric.
- Sporulation. It consists of the production within the cell or in specialized organs (sporangia, for example), of cells wrapped in a super resistant covering, known as spores. They are able to survive long periods and very hostile conditions, and then produce a new individual when the environment is conducive.
- Parthenogenesis. The new new individual is created from the development of unfertilized female sex cells. Therefore, it is genetically equal to the parent. Some animals can perform it, such as flatworms, rotifers, tardigrades, insects, amphibians, fish and crustaceans, but also some reptiles.