Protist Classification (continued)


Its cell is elongated, may have one or more flagella and in some there are also pseudopods. In the genus Trypanosoma there is an undulating membrane that aids in locomotion. Near the point of origin of the flagellum is the kinetoplast, the DNA-containing organelle, capable of self-duplication and enclosed within a long, irregularly shaped mitochondria that extends throughout the cell.

There are flagellates of free life (Euglena - have chlorophyll and perform photosynthesis; they can also nourish heterotrophically = zooflagellates), mutualistic (Trichonympha, in the termite gut - provide the cellulase enzyme) and parasites (Trypanosoma cruzi).

In choanoflagellates, there is a kind of collar that serves to capture food particles; They have a structure very similar to the choanocytes, typical sponge cells.

Because of this, there are theories that suggest a phylogenetic relationship between choanoflagellates and sponges.


Reproduction is sexed or asexual by longitudinal division.

This phylum has many important human parasites:

- Leishmania braziliensis: Causes cutaneous leishmaniasis or Bauru ulcer ('wild wound'). It lives inside the skin cells and is transmitted by the straw mosquito (birigui).
- Trypanosoma cruzi: Causes Chagas disease, common in our country and in South America is transmitted by bed bugs popularly known as barbers.
- Giardia lamblia: Causes giardiasis (intestinal).
- Trichomonas vaginalis: Causes trichomoniasis (in the genital tract).

In the gut of termites and cockroaches that eat wood there are flagellates. This coexistence is peaceful and characterizes an association in which both participants benefit (mutualism). Wood eaten by insects is digested by enzymes produced by flagellates. Both take advantage of the products of digestion.

Sporozoa or Apicomplexes: They Are All Parasites

They have no organ for locomotion.

Are all parasites and feature a special kind of asexual reproduction called sporulation: a cell divides its nucleus numerous times; each nucleus with a little cytoplasm is then isolated by a membrane, thus forming several spores from one cell

In the life cycle they present alternation of reproduction asexual and sexed.

The main genre is the Plasmamodium, with several malaria-causing species. O Toxoplasma gondii, causative of toxoplasmosis disease, is of great seriousness in pregnant women until the third month.

It is the most highly specialized group. Present eyelashes, cirrus and membranes. These last two structures result from the concrescence (union) of many eyelashes. Among them are the "giant" protozoa such as the paramecium (Paramecium) widely used in studies; Here are the protozoa of the most complex organization. Paramecii move much faster than flagellates and amoebae because of the numerous lashes protruding from the body wall. Most are free living.

In addition to specialized organs, they have two nuclei: macronucleus (vegetative functions) and micronucleus (genetic functions: heredity and reproduction); have anterior and posterior extremities; in the membrane, food enters through the cytostome and the waste output by the cytopigy (= cytoprocyte).

They have two pulsatile vacuoles that function alternately effecting osmotic regulation and possibly expelling toxins. Each vacuole has channels that collect cellular water, directing it to a reservoir that expels it from the cell.

Gas exchange and excretion, as in other protozoa, occurs across the cell surface. THE asexual reproduction, as in amoeba and euglena, occurs by binary division.

THE sexual reproduction by conjugation It consists in the pairing of two parameciums, with membrane fusion and then exchange of genetic material from the micronuclei. Then the paramecians separate and reproduce asexually by cissiparity.