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Biology 2014-2015

Protozoa Notes
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    The kingdom Protista includes more than 200,000 species.

    A protist is any organism that is not a plant, an animal, a fungus, or a prokaryote.

    Protists are microscopic, unicellular, animallike organisms that carry on all life sustaining functions.

 

HOW ARE THEY CLASSIFIED?

    Based on the way they obtain nutrition.

       Animallike protists - heterotrophs

       Plantlike protists - photosynthesis

       Funguslike protists - decomposers or parasites

 

ANIMALLIKE PROTISTS: PROTOZOANS

    Animallike protists were called protozoa, which means "first animals".

    Four phyla of animallike protists are distinguished from another by their means of movement

       flagella, pseudopods, cilia, no movement

 

Sarcodines

    phylum Sarcodina, or sarcodines

    move via temporary cytoplasmic projections known as pseudopods

    Amoebas are the best known sarcodines.

    In an amoeba, the cytoplasm is constantly flowing.

    The streaming cytoplasm pushes against the cell membrane pushing out projections called pseudopodia.

    Pseudopod means false feet.

    This type of locomotion is called amoeboid movement.

    They are found in the slime at the bottom of streams and ponds, and on water plants.

    Oxygen and water dif fuse through the cel membrane. Water enters by osmosis and is always being removed by the contractile vacuole.

    Amoebas get food by surrounding their food (cells of algae and other protists) with their pseudopodia. The food is taken in by a food vacuole.

       A food vacuole, is a small cavity in the cytoplasm that temporarily stores food.

    Digestion takes place by enzymes produced in the cytoplasm that pass into the vacuole. Particles that can -not be digested or not used remain in the vacuole and are then released from the cell.

    Amoebas reproduce by mitosis and cytokinesis.

    Amoebas are sensitive to light and dark. Also, dryness, cold, or lack of food.

    If conditions are not correct then they form a cyst until conditions improve and they become active again.

 

Ciliates

    phylum Ciliophora

    Move by using cilia which are short hairlike projections

    The cilia beat back and forth like little oars and can beat either forward or backward.

    Live in both fresh and salt water

    Paramecium is the best known ciliate.

    The paramecium does not change shape like anamoeba but has a thick outer membrane called a pellicle.

    Trichocysts are their defense mechanism. These fire out when a larger protists nears. They give the paramecium a bristly or rough appearance.

    A paramecium possesses two nuclei:

                        1. Macronucleus - which controls normal cell activity or the "working                             library" of genetic information

                        2. Micronucleus - which aids during cell reproduction or the

                                    "reserve copy" of all the cell's genes.

    Paramecium sweep in food particles through their oral groove towards the gullet. There is a front and back to the paramecium. The oral groove runs from front to back.

    Particles trapped in the gullet are forced into a food vacuole that forms at its base.

    The food vacuole breaks away into the cytoplasm and fuses with lysosomes, which contain digestive enzymes.

    Food is digested and absorbed with undigested food passing through the anal pore.

    Oxygen dissolved in the water diffuses throughthe cell membrane and enters the cytoplasm. Here it is used for respiration and the carbon dioxide is released back through the cell membrane.

    Paramecium have a contractile vacuole with canals. The canals fill with water and then pass it onto the contractile vacuole where excess water is pumped out of the organism.

 

 

 

 

 

    Most other wastes diffuse out of the cell membrane.

    They move and respond in a "trial and error" fashion. Moving forward until they bump into something, then they reverse. This is called the avoiding reaction.

    They are reproduce asexually by mitosis and cytokinesis

    When placed under stress, they may engage in conjugation. It is not a form of reproduction but it is a sexual process. The two paramecium meet and exchange micronuclei and then divide by fission. This adds variation and maintains genetic diversity.

    

Zooflagellates

    phylum Zoomastigina or zooflagellates

    swim by using flagella which are long, whiplike projections

    absorb food (decaying organic material) through their cell membrane

    live in lakes and streams

    live within the bodies of other organisms

•reproduce asexually by mitosis and cytokinesis (genetically identical)

    sexually, gametes are produced by meiosis

 

Euglenophytes

    phylum Euglenophyta or euglenophytes

    plantlike protists that have two flagella but no cell wall

    they move in two ways: one by twirling the flagellum to push them forward, or two: by inching forward like an inchworm

    found in ponds and lakes and are excellent swimmers

    anterior end is rounded, posterior is more pointed

    the red eyespot is sensitive to light

    they seek out bright areas to live which is unlike many other protozoas

    euglenas have chloroplasts but if sunlight is not available, they live as heterotrophs absorbing decayed organic material

    euglena reproduce asexually by binary fission

    Under good conditions, they can divide once a day. In great numbers, they will make the water appear green.

 

Sporozoans

    phylum Sporozon

    protozoans that do not move on their own and are all parasites.

    live by absorbing food from their host

    some of the organisms live in one host per lifetime others two.

    They reproduce by means of sporozoites attaching to a host cell, penetrating it and living within it as a parasite.

 

ANIMALLIKE PROTISTS AND DISEASE

 

Malaria

    caused by the sporozoan Plasmodium which is carried by the female Anopheles mosquito

    Life Cycle:

            1. Transmitted to humans by the female Anopheles mosquito

            2. The mosquito's saliva contain the sporozoites and enters the human's

                        bloodstream

            3. Once inside, plasmodium infects liver cells, then red blood cells and

                        multiplies rapidly

            4. Red blood cells burst releasing parasites into the bloodstream causing

                        severe chills and fever

 

African Sleeping Sickness

    Trypanosoma, a zooflagellate, is responsible for African sleeping sickness.

    It is transmitted to humans by the bite of the tsetse fly.

    symptoms include chills and rashes and can also infect nerve cells.

    Some individuals lose consciousness, lapsing into a deep and sometimes fatal sleep.

 

Amebic Dysentery

    characterized by severe diarrhea and is caused by an organism that looks like a harmless ameba.

    Entamoeba, a parasite spread by contaminated drinking water attacking the walls of the intestine and causing extensive bleeding.

    it is most common is areas with poor sanitation.

    But even crystal-clear mountain streams may be contaminated with a flagellated pathogen called Giardia that causes severe diarrhea and digestive problems.