Chp. 26 Notes The Protista Kingdom Most protists are unicellular, microscopic organisms, but a few are complex and multicellular. These are the most diverse (different) organisms according to life cycles, since they reproduce asexually and sexually. This kingdom contains ancestral life-forms that gave rise to three kingdoms of multicellular organisms--the fungi, the plants and animals. As we talked about the theory of endosymbiosis, we should now be able to understand that early in the development of our planet, scientist feel that prokaryotic organisms were the only forms of life on our planet. As time went on, these organisms were invaded by parasites which eventually lost their ability to live outside the host cell and became organelles of the host. This brought about the Eukaryotic cells. Protist organisms exibit the most basic characteristics of these eukaryotic cells as well as some complex characteristics involved in organisms within the fungi, plant and animal kingdoms. Several features evolved as did the eukaryotic cell. These characteristics that evolved in protist organisms are; 1) Multicellularity- The prokaryotic bacteria are the only groups of organisms which are soley unicellular. Most protist are unicellular but there quit a few groups of multicellular organisms in this kingdom as well. 2) Sexual Reproduction- All prokaryotic organism asexually reproduced which meant that they reproduced an exact copy of the parent organism unless a mutation occured in the offspring. With protist organisms sexual reproduction came about as a form of necessity due to environmental stresses ( ie. lack of nutrition, temp. change, predation. etc.) Sexual reproduction brings about genetic variation without mutation needing to occur due to there being two parent organisms producing offspring. 3) Complex development of the Cilia and Flagella- is another characteristic which evolved in the protist group. In bacteria the flagella were just a single protein filament (basically solid in structure) but in the protist, they had cilia and flagella develop with the 9 & 2 principle. 9 pairs of microtubules surrounding 2 microtubules. A microtubule is a hollow protein filament. These hollow filaments allowed for easier movement and lighter weight, which allowed them greater range of motion in the movement of these structures. Differences between Cilia and Flagella a) cilia are short hairlike projections which are used for movement of either the organism or materials around or through an organism. There are usually hundreds of these per cell. b) Flagella are long whiplike structures used primarily for movement ( locomotion). There are usually one or two pair. 4) Eyespots- another characteristic to emerge in this group is the eyespot which is sensative to the quantity or quality of light. Some protist are heterotrophic but must reside in a moist environment. With light comes heat and desication( drying out) so they must stay away from the light. Others are photosynthetic and aquatic and need the sun to maintain photosynthesis, so they need to go toward light sources.
Environments we find protists in. a) Aquatic - means any place we find water 1) Marine- Saltwater, oceans 2) Freshwater- Lakes, Ponds, & streams b) Leaf litter or damp places c) Moist Sand or Soil d) Body fluids of tissues of organisms e) Blood streams of organism. Why do these organisms need to be located in moist environments? The reason or answer to this question, is due to the fact that these organisms do not have any ability to keep moisture in their structure, like plants which have a cell wall to help retain moisture, and humans who have skin to keep moisture in so therefore they have to live in a moist environment. Various types of Protistes Reproduction in Protist. Asexual Reproduction by Binary Fission or Multiple Fission Binary Fission- is a single cell splitting into tow cells that are identical Multiple Fission- is when a single cell splits into 4 or more cells at a single time, thus forming multiple offspring that are identical Most protist organisms reproduce asexually as a general rule. Environmental Stress will cause the organisms to reproduce Sexually. The 3 basic types of environmental stress that effects all living organisms is temperature, moisture, and nutrition. Either the lack of or too much of each of these environmental factors will bring about sexual reproduction in the protist organisms. The 3 types of Sexual reproduction are: 1) Conjugation- This process happens between many types of filamentous algae, in which two filamentous algae, while aligned next to each other, will form a conjugation tube between each filament. The tube will extend from one cell in the filament to a cell in the other filament. The haploid nuclei from each cell will travel through the conjugation tube and fuse together, forming a diploid zygote. This diploid zygote will then undergo meiosis to produce 4 haploid cells again which will develop into new filaments and mature. 2) Gamet Production- Here again this usually occurs with filamentous algae, but now there are specialized cells in each filament which produce and hold egg and sperm structures. The sperm are released from one cell in a filament and go through the water to fertilize the egg in a different filament. This will bring about offspring with characteristics from each of the different filaments. 3) Alternation of Generations- IN this reproductive process, there are two phases to the reproductive life cycle in these algae. 1) Asexually the organism goes through mitosis to produce diploid or exact replicas of the parent cells. 2) Sexually the organism goes through in another phase of its life cycle meiosis
which produces haploid cells. Protista the Catch All Kingdom This kingdom is called the catch all kingdom because these organism lack the specific characteristics that would put them into the other three kingdoms, fungi, plant, and animal. Animals- Are all heterotrophic, multicellular, sexually reproducing organism which only have a cell membrane and no cell wall present. Plants- Are all autotrophic, multicellular, mostly sexually reproducing( few asexual forms) which have a cell wall made of cellulose and a cell membrane. Fungi- Are mostly multicellular ( few are unicellular), heterotrophic, sexually and asexually reproducing organism, with a cell wall of chitin instead of cellulose like plants Types of Movement Protist Phylum Sarcodina Ameboes & Forams These organisms move by using a process called pseudopodia (false foot). Pseudopodia are cytoplasmic extension of the cell cytoplasm. The cell membrane of these organisms allows them to change shape. Pseudopodia are formed by a process called cytoplasmic streaming which is the cytoplasm constantly moving, the rest of the cell will follow the pseudopod. Human Disease from Sarcodines is Amebic Dysentery which causes severe cramping, diahrrea and nausea. Phylum Zoomastigina commonly called the flagellates Flagellates- are protist which use flagellas to move. There are 3 major phyla of flagellates. Dinoflatellates- unicellular, photosynthetic protist, usually with 2 flagella, usually in marine environments, but we do find some in freshwater. Some dinoflagellates produce toxins (poisons). Red Tide is a phenomena that occurs when there is a rapid population increase in these protists and as aquatic organisms or humans consume them, they too become poisoned with the toxin. Some are bioluminescent which means they produce a light as they live that is given off.(like Fireflys) Introduction to the Dinoflagellata Zoomastigotes- unicellular, heterotrophic, protist with at least one flagellum.
Trychonympha is a zoomastigote that live in the gut of termites where they provide the enzymes that digest wood. Trypanosomes are zoomastigotes are dangerous pathogens in humans and domestic animals. Diseases Caused by Zoomastigina Phylum 1) Trypanosomiasis- African Sleeping Sickness 2) Transmitted by the Tsetse fly 3) Symptoms are fatigue and intense fever, and may even cause comma and death. Chagas Disease 1) The kissing bug found in foundations of poorly maintained houses is the transmitting agent of this disease. The feces of the bug can cause infection through improper hygien. Leshmaniasis- 1) Transmitted by the sand flies 2) Produces skin ulceration and sores, which will eventually spread throughout the skin. Girardiasis- often associated with beaver dams and the water contained in the stream. 1) Transmitted by drinking the contaminated water 2) Produces symptoms of cramping, diharrea, and nausea Euglenoids- are freshwater protist with 2 flagella. 1/3 of these are photosynthetic, the rest are heterotrophic, the euglena is the common example we use in study in biology. Ciliates- are protists that have cilia for swimming. The paramecium is the common example used in study of biology and have large numbers of rows of cilia surrounding their cell surface. Phylum Sporozoa 1) This phylum has no movement or locomotion 2) Many have complex life cycles that involve two or most host organisms. Toxoplasmosis- is a disease caused by a sporozoan that we get usually from our household cats. The disease is often carried by birds, or rodents, which cats may eat and then transmit to us. It has little affect on us if we have strong immune systems, but may greatly affect the elderly and young children. Plasmodium- Malaria 1) has symptoms of fever, chills, fatigue and great thirst 2) People die of anemia, kidney failure, and brain damage 3) The female anopholes mosquito is the transmitting agent, males eat only plant tissues. 4) Life cycle a. Sporozoite cells- are taken in by the host when a mosquito bites a human.
b. Sporozoite cells migrate to the liver and undergo rapid reproduction to produce Merozoite cells c. Merozoite cells, go and infect the red blood cells and cause them to rupture and die. This releases more merozoite cells and they go and infect other RBC s d. Gametocytes are picked up by a mosquito that bites an infected person. e. Gametocytes in the guts of the mosquitoes will develop into sporozoite cells and the cycle is ready to start all over again. Protist Diversity We have already talked about the amoebas which are unicelluar and very simply constructed organisms.there are several others we need to mention to show how different various protist are. Diatoms- Are more commonly found in Lakes & Oceans. These organisms have a shell composed of Silica. Silica is a material that is made into many products, such as glass and other materials. As diatoms reproduce asexually their shell continues to get progressively smaller. Eventually they outgrow their shell and discard it. As discarded shells setttle to the bottom of the aquatic floor, they form a layer of earth called diatomaceous earth, which is mined for the silica. This material is used commercially as an abrasive in cleaners like toothpaste and also used as the reflecting material found in roadway marking paint.