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Phylum Protozoa Ameba, Euglena Lyrics and Vocal: Shin Kubota, Music: Shiori Nakagita |
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How and what did the ancestor of animals, which appeared on the primitive earth, shape, forms and evolve into multi-cellular organisms? Protozoa has the keys to the answers. Protozoa, which are made up of a single cellular body, are present anywhere in the water and known to inhabit under the ground as well. At least 31,000 species are known to us. They are miracle organisms that can only be seen under high magnification, but electron microscope observation of micro structures and phylogenic analysis using molecular biology technique enabled us to drastically advance our knowledge on this creature. Therefore, classification methods to assign the member of this phylum has changed and, based on certain classification methods, the phylum protozoa may not belong to the animal kingdom. Furthermore, various opinions exist on evolution of multi-cellular organisms from this creature. The ancestor of multi-cellular animals is colonial flagellates. A certain species of single cellular flagellates gathered together and formed colonies and, according to some hypothesis, they eventually evolved into multi-cellular sponge. No one knows for sure if single-celled flagellates colonize and spend long time enough, cells will differentiate and develop into the organized multi-cellular animal that has order and control. The mystery is deepening. Let’s introduce some members of Protozoa. Among the animal-like and plant-like fellow “dinoflagellates”, Noctiluca is known to cause damages to aquaculture and it glows pale. Zooxanthella, which lives symbiotically in the cells of stony corals and bivalves and gives them nutrition via photosynthesis, is also in this group. The body of amoeba is amorphous and can change to various shapes. Although they do not have hair (flagella and cilia) on their body surface for locomotion, they form fake feet (pseudopodia) and elongate their body to move around. Pseudopodia are also used to uptake microbes and digest them for nutrition. The ameba may be aquatic or terrestrial, but all the ameba species asexually reproduce by fission. Thus, there is no male or female individual, they do not produce an egg or sperm, and no sexual reproduction takes place. There was a group like Arcella which has a shell (test) and its fossils are found from the last Paleozoic Era some hundreds of millions years ago. Star-shaped sands well known in a tropical region are the foraminiferas which extend pseudopodia from the countless holes in calcareous tests to collect food. Their shapes are easily visible to the naked eye, and are wonderfully large-sized for a single-cell organism. A large sized species looking like a round cookie is a member of benthos who lives on the seabed, and its diameter is several centimeters wide. A member of such group is the fossil of the nummulites that can reach diameter of 10 cm and are gigantic. Radioralians are marine plankton and can extend as many as several hundred axial filaments which look like needles. They have pseudopodia that may cover the filaments and increase the surface area to control buoyancy. Foods are taken in by contracting the axial filaments. Notorious for causing illness to humans, malaria parasites also belong to this phylum. Moreover, Euglena that has both animal and plant characteristics, swims around by beating a long flagellum. They can photosynthesize because they have chlorophylls, and the fact that they catch and eat microbes makes them both animal-like and plant-like organisms. |
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Less than 1 mm, the Protozoa is so small |
I am sorry.
A song is only Japanese.
Song
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karaoke
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Copyright (C); 2007, Shin Kubota.All Rights Reserved.