Class Mastigophora

The superclass Mastigophora (or Flagellata) includes those protozoans that possess flagella as adult locomotor organelles; it is generally considered to be the most primitive of the major protozoan groups. Since flagellates cannot make their own food, most of them take in tiny pieces of food from the water where they live. But some are parasites. These flagellates live on or inside other living things and feed on them. Many cause disease. Mastigophorans are conveniently divided into the phytoflagellates and the zooflagellates.

The zooflagellates (class Zoomastigophorea) possess one to many flagella, lack chromoplasts and are either holozoic or saprozoic. The zooflagelates are regarded as the most primitive of the Protozoa and also as a link between the algae and the protozoans. They are thought to have been derived from photosynthetic forms. Some are free-living, but the majority of species are commensal, symbiotic, or parasitic in other animals, particularly arthropods and vertebrates. Many groups have become highly specialized. It is generally agreed that this division does not represent a closely related phylogenetic unit. The zooflagellates have probably evolved from a number of different holophytic groups through the loss of pigments. The zooflagelates multiply asexually by mitosis and cell division. The parasitic forms include Trypanosoma gambiense, a flagellate that causes African sleeping sickness, and members of the genus Trichonympha, complex and beautiful flagellates that live as symbionts in the digestive tracts of termites where they digest the wood ingested by the termite.

5.1.2. Class Sarcodina

The sarcodines are amoeba-like organisms which have no coat or wall outside their cell membranes and which generally move and feed by the formation of pseudopodia. They move by changing shape. The shape changes to form fingerlike parts known as pseudopodia, or “false feet”. For the amoeba to move in another direction, it must form new pseudopodia on that side of the body. Despite their uncomplicated appearance, they are complex cells and are even capable of some complex behavior patterns, as when sensing and pursuing prey organisms. Amoebas take in food by forming pseudopodia around each peace of food. When the food is surrounded, a food vacuole is formed around it and it is moved inside the cell. Reproduction may be sexual or asexual. Many of the sarcodines cover their amoeba-like characteristics with firm bright shells. Their shells are made of calcium carbonate, extracted from water. It is possible to date a particular stratum by the type of Foraminifera that it contains, a fact that has proved of immense practical value in locating oil-bearing strata in Texas, Oklahoma and many other oil-rich areas.

Some cause amoebic dysentery.

Date: 2014-12-22; view: 1334