Information

Protist Classification


The classification of protozoans is fundamentally based on the types of reproduction it's from locomotor organelles.

The locomotion is done by heartbeat ciliary, scourge, per pseudopod emission and even for simple full body cell slip. In some ciliates there are, instead of the cytoplasm, contractile filaments, the myonemes. Although pseudopods are variable expansions of the cytoplasm, they may be present in different forms.

In the modern trend, protozoans are included in the Protist Kingdom, subdivided into four phyla:

They are amoebas (“naked”); radiolarians and foraminifera (they have very showy carapaces made of limestone or silica - important indicators of the existence of oil deposits)

They are marine, freshwater or parasitic (Entamoeba histolytica). They have one or more nuclei, digestive vacuoles and contractile vacuoles (freshwater only).

The rhizopods are characterized by their pseudopods as a structure for locomotion and food capture. These are projections of the entire deforming cell that move the amoeba in various directions. The mechanism leading to pseudopod formation is now fairly clear: in the region of formation of one of these projections, the viscous part of the cytoplasm becomes fluid, allowing the rest of the cell to flow in that direction. Several pseudopods can be formed at the same time, constantly changing the shape of the amoeba. Pseudopods in the amoeba are not just for locomotion. Also used for food capture: small algae, bacteria, loose particles in water etc. They surround the food and encompass it.

O food vacuole formed (also called a phagosome) binds to lysosome and becomes a digestive vacuole. Digestion begins from lysosomal enzymes that act in an acid medium. Progressively, the content of the digestive vacuole becomes alkaline until digestion is complete. Digested particles cross the vacuole membrane, spread throughout the cytoplasm and will participate in cellular metabolism. Residual particles are expelled from the cell by fusion of the vacuole wall with the cell surface in a reverse process to phagocytosis.

Free-living amoebas living in freshwater have contractile vacuole or pulsatile for osmoregulation, eliminating excess water entering your cytoplasm (hypertonic) from the more diluted (hypotonic) environment.


Microscopy of a risopod

Under unfavorable conditions, for example subject to dehydration, Entamoeba produces resistance forms, the cysts, with four nuclei inside (multiple partition).

THE asexual reproduction it's for simple split or cissiparity (mechanism similar to mitosis).

Among amoebas is important Entamoeba histolytica, which parasitizes the human intestines, causing amoebic dysentery or amoebiasis.