Amoeba

What is Amoeba?

An amoeba is a simple eukaryotic organism that moves around through Pseudopodia (cytoplasm pushing the cell membrane); the word pseudopodia means ‘false feet’. They are commonly found on freshwater surfaces such as ponds and rivers. The ability to change its body shape as required is the key feature to amoebae (plural). 

The scientific name of amoeba is “Amoeba proteus”, also termed as the genus name. Amoeboid cells are generally found within animal species, some forms of algae and even in fungi. Asexual reproduction is the typical nature of amoebic cells and the cells multiply through a biological process called binary fission (or multiple fission). 

Hence when it comes to defining what is amoeba - a single-celled protozoan that uses pseudopodia to move and engulf its prey and even causes illness and different brain infections in human beings. Amoebic Dysentery or Amebiasis infection due to “Entamoeba histolytica” is a classic example. 

[Image will be Uploaded Soon]

The Structure of Amoeba      

Accounting to the amoeba’s characteristics, its cytoplasm along with cellular contents enclose within a cell membrane. The DNA is bundled into the main cellular compartment, called the nucleus and is covered by the plasmalemma. The nucleus comprises other several membrane-bound genetic organelles that help in protein transportation and produce energy. To name a few:

  • Contractile vacuoles (osmoregulation subcellular structures)

  • Golgi apparatus (a folded membrane with vesicles)

  • Fat globules (the hydrophobic intracellular pieces)

  • Food vacuoles (a storage unit for every food)

  • Water globules (small, colourless, spherical vacuole water elements)

  • Mitochondria (the powerhouse of a cell)

Speaking of its cytoplasmic entity, an amoeba has 2 layers namely inner endoplasm (granulated) and outer ectoplasm (non-granulated). The entire body of an amoeba is transparent and looks similar to gelatin. 

When it comes to the food consumption process of an amoeba, a prey is usually ingested either through pinocytosis or phagocytosis. Adding to this, an amoeba can turn itself into a microbial cyst, when its food and living food conditions are abnormal. Bacteria, plant cells, metazoa, algae, protozoa are some of the common examples of what an amoeba eats. Yet, it does not have a well-defined mouth or anus for secretion or excretion. 

Since every amoeboid cell is a pseudopod, it does not have a definite shape. However, the size of an amoeba cell is around 250 and 750 microns. There are even amoebae that are visible to a human’s naked eyes. Moreover, A. Proteus is the biggest known cell in the unicellular kingdom of organisms. 

Amoeba Classification     

The classification of amoeboid cells has a few critics since it possesses only a true nucleus and is neither an animal nor a plant. To maintain consistency, ameboid cells are classified commonly under the Protista Kingdom. 

Following below is the scientific representation of the amoeba classification:

  • Domain: Eukaryota

  • Kingdom: Amoebozoa

  • Phylum: Tubulinea

  • Order: Tubulinida

  • Family: Amoebidae

  • Genus: Amoeba

  • Species: Proteus, animalcule, dubia, animalcule, etc.

Current research studies focus on classifying amoeboid cells using their subunit ribosomal RNA (SSU rRNA) genes. 

‘Sarcodina’ is the single-most acceptable taxonomic group for the classification of amoeba cells. This is classified based on certain observable characteristics and after studying its morphology. Note that this classification is not based on any evolutionary relationship and hence it is not be considered as a family tree. 


FAQ (Frequently Asked Questions)

1. Is Amoeba Unicellular?

Yes. Amoeba is a single-celled eukaryotic organism that does not have a definite shape due to its pseudopodia. 

2. Who Discovered Amoeba?

August Von Rosenhof, who was a German naturalist,  miniature painter and an entomologist discovered amoeba in 1755. He was a significant contribution to the field of modern entomology. 

3. Why is Amoeba Called Immortal?

2 days is the general lifespan for an amoeba cell. Yet the daughter cells produced through binary /multiple fission is the replica of the parent cell. This is 1 reason why amoeba is immortal in technical aspects.

4. At What Level of Organization is an Amoeba?

Ameboid cells will not be considered for a single taxonomic group. But they occur in multiple lineages of eukaryotic organisms. Examples include bacteria, fungi, protozoa, etc.

5. Can Amoeba Regenerate if Cut?

Yes. Amoeboid cells have the capacity of regeneration after cutting into pieces. Each piece cut will regenerate and form a new amoeba. But if a fragment does not have its nuclear components, then it cannot regenerate.