Protists
- Protists are eukaryotes; not members of the plant, animal, or fungi kingdoms.
- Some protists are more like members of other kingdoms.
- all eukaryotes evolved from prokaryotes. animals, plants, and fungi evolved independently from the ancestors of today’s protists.
- protists are more complex than prokaryotes.
- most of the major protist groups have remained unicellular, but two have produced organisms that developed true multicellularity. It is from the ancestors of these groups that plants, animals, and fungi arose.
-plants, animals, and fungi evolved from ancestors of today’s protists.
Motion
These structures supported by microtubules. They have nearly identical internal structures, but they produce different cellular motion.
- cilia (singular: cilium) are short and numerous, and they move somewhat like oars on a boat. cilia are evenly spaced and beat in a regular, efficient pattern.
protists that move by way of cilia are called “ciliates.”
-flagella(singular: flagellum) flagella are relatively long and few, are at the end of the organism and move from side to side. , and is like the back-and-forth movement of a single long oar at the back of a boat, propelling it forward. flagella are spaced on one end protists that move by way of cilia are called “flagellates.”
-Many unicellular protists change their shape that makes use of cytoplasmic projections known as pseudopods (false feet). Amoeba
-Some protists are non motile they depend on air or water or other organisms to carry them around. These protists form reproductive cells called spores that can enter cells as parasites.
Reproduction
Paramecium has two kinds of nuclei, one is a large ellipsoidal nucleus called a macronucleus and other is (at least) one small nucleus called a micronucleus. Paramecium cannot survive without the macronucleus whereas it cannot reproduce without the micronucleus.
Binary fission is a type of asexual reproduction typically observed in prokaryotes and a few single-celled eukaryotes. In this method of asexual reproduction, there is a separation of the parent cell into two new daughter cells. This process happens with the division and duplication of the parent’s genetic matter into two parts.
Conjugation, in biology, sexual process in which two lower organisms of the same species, such as bacteria, protozoans, and some algae and fungi, exchange nuclear material during a temporary union (e.g., ciliated protozoans), completely transfer one organism’s contents to the other organism (bacteria and some algae), or fuse together to form one organism (most bacteria and fungi and some algae).
Many protists have complex sexual life cycles in which they alternate between a diploid and a haploid phase, a process known as alternation of generations. An example is the life cycle of a type of protist known as a water mold. Water molds, or oomycetes, thrive on dead and decaying organic matter in water or as parasites of plants on land.
-water molds grow into long branching filaments consisting of many cells formed by mitotic cell division. Water molds—and many other protists—reproduce asexually by producing spores in a structure called a sporangium.
-water molds also reproduce sexually by undergoing meiosis and forming male(1N) and female structures. These structures produce haploid nuclei that fuse during fertilization (egg 1N), forming a zygote(2N) that begins a new life cycle.
Role in environment
Three roles include autotrophic protists, mutualists, and parasites.
-photosynthetic protists play major roles in maintaining the health and well-being of many organisms and ecosystems. The position of photosynthetic protists at the base of the food chain makes much of the diversity of aquatic life possible.
| Providing Food | Photosynthetic protists make up a large portion of phyto-plankton found near the surface of oceans and lakes. Abouthalf of the photosynthesis that takes place on Earth is carriedout by phytoplankton, providing nourishment for organismsas diverse as shrimp and baleen whales. |
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| Supporting Coral Reefs | Coral reefs provide food and shelter to large numbers of fish and other organisms. Protists known as zooxanthellae providemost of the coral's energy needs by photosynthesis. By nourishing coral animals, these algae help maintain the health andequilibrium of the coral ecosystem. Coralline red algae also help to provide calcium carbonate to stabilize growing coralreefs. |
| Providing Shelter | The largest known protist is giant kelp, a brown alga. Kelpforests provide shelter for many marine species, and the kelpitself is a source |
types of symbiosis: mutualism (both species benefit), commensalism (one species benefits and the other is neither harmed nor helped), and parasitism (one species is helped by harming the other).
-parasitic protists are responsible for some of the world’s deadliest diseases, including several kinds of debilitating intestinal diseases, African sleeping sickness, and malaria. Waterborne protists are found in streams, lakes, and oceans. Most cause little harm to humans, but some of these microorganisms are parasites that cause serious problems.
| Mutualism | Many protists are involved in mutualistic symbioses, in which they and their hosts both benefit. One example is a mutualistic relationship involving Trichonympha. This protist lives within the digestive systems of termites and helps to produce enzymes that enable the termites to digest wood. |
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| Parasitism | -malaria, caused by a protist known as Plasmodium. This parasite lives in the human bloodstream, and is passed from person to person by the bite of the Anopheles mosquito, which is common in tropical regions. In years past, malaria killed as many as a million people a year, many of them children. Developing drugs and vaccines to fight this killer has been a major effort of the World Health Organization. This effort has cut the death rate from malaria by as much as 50 percent in some regions.-Giardia (are intestinal pathogens, and are passed out of the body in feces. In places where sanitation is poor, the protists may contaminate water supplies and food.They are primarily spread via recreational waters, such as lakes, swimming pools, and water parks. Many cases of Giardia are also transmitted directly from person to person. ) are responsible for serious, and sometimes deadly outbreaks of intestinal disease.-Trypanosoma cause African sleeping sickness. |