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KINGDOM PROTISTA. PROTISTS. Very diverse group >60,000 known species Most are unicellular Some are colonial Some are multicellular Not “simple” at the cellular level A unicellular organism must carry out all basic functions of life within a single cell
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PROTISTS • Very diverse group • >60,000 known species • Most are unicellular • Some are colonial • Some are multicellular • Not “simple” at the cellular level • A unicellular organism must carry out all basic functions of life within a single cell • Cells within a multicellular organism can become specialized, and need not carry out all such functions
Protists show amazing diversity in cell organization, methods of reproduction, metabolic needs and habitats. • They inhabit aquatic and terrestrial environments. • Protists are the most nutritionally diverse eukaryotic group • Most are aerobic, and possess mitochondria • Some protists are heterotrophic; others are autotrophic
Protists are divided into 3 main groups • Animal-like protists (Protozoa) • Plant-like protists (Algae) • Fungus-like protists
Animal-like Protists • All protozoa are heterotrophic • Some absorb nutrients through their cell membrane, whereas others “engulf” larger food particles. • Most protozoa are motile and are divided into phyla based on their means of locomotion.
Phylum Sarcodina • Ancestors lost their permanent motile structures. • Found in fresh and salt water and inside the bodies of animals. Some of these cause disease. • Reproduction is both sexual and asexual.
Types of Reproduction • Asexual Reproduction - only one parent is needed, resulting in offspring that are genetically identical to the parent -- clones. • Sexual Reproduction - requires two parents who exchange genetic material, resulting in offspring with a mix of inherited genes.
The best known sarcodine is the ameba. • Amebas are unicellular organisms that continually change shape • Move and capture food by pseudopods, or “false feet.” • This movement by pseudopods is called amoeboid movement. • Amebas reproduce asexually by binary fission. • They are commonly found in freshwater ponds, lakes and streams.
Amebas can cause disease! • They can cause amebic dysentery. • Common in tropical regions • Lives in the large intestine of humans and feeds on the intestinal wall causing bleeding. • A person becomes infected by eating food or water contaminated with the cysts of the ameba.
Radiolarians and Forams • Also belong to the phylum Sarcodina. • Surrounded by protective shells that contain silicon. They have very long thin pseudopods. • When these organisms die, their shell settle to the bottom of the ocean.
Phylum Ciliophora • e.g., Paramecium • Many possess numerous cilia • Motile structures • Beat in synchronized fashion • Prey on bacteria, algae, each other • ~65% are free-living and motile • Others attach to some substrate • Some form colonies
A Microscopic Predator – two ciliates meet for lunch Didinium sp. Paramecium sp.
Cilia are important in movement and to move food into the oral groove. • Food particles are enclosed and digested in food vacuoles. • Some ciliates have contractile vacuoles which collect and excrete excess water from the cell. Most aquatic protists have a contractile vacuole.
Ciliates do not change shape. • They have a rigid outer covering called a pellicle that maintains their shape. • Beneath the pellicle, some ciliates have trichocysts which are barbed structures that are discharged for defense or capturing of prey.
Reproduce sexually and asexually • Similar to most protozoans in this regard • Asexual process is “binary fission” • In this process the cell divides into two genetically identical cells. • Sexual process is “conjugation” • Two cells join and exchange their micronuclei before the cells divide.
Phylum Zoomastigina • Also called the zooflagellates. • These protists move by beating a long whip like flagella. • Some have one flagella while others may have many. • Most are unicellular. • Some are free living but most live in the bodies of animals. • Reproduce both asexually and sexually.
African Sleeping Sickness • The parasite multiplies in the blood and releases toxins that cause fever, weakness and sleepiness. • Lives in the blood of wild and domestic animals, but can be passed to humans through a bite from a tsetse fly.
Not all zooflagellates are harmful! • Another zooflagellate lives in the digestive tract of termites. • The protist breaks down the wood that the termite eats and then both absorb the nutrients.
Phylum SPOROZOA • These are non motile parasitic protozoa. • They get their name because they produce spores during asexual reproduction. • The spores allow the spread of the parasite to new hosts. • The life cycles of sporozoans are complex and involve growth and reproduction in more than one kind of host. • The best know members are of the genus Plasmodium, which causes malaria.
MALARIA • Has infected > 100 million people • ~1 million die yearly in Africa alone • Shaking, chills, fever, sweats caused by the toxins that are released when the red blood cells of the host are destroyed by the reproducing Plasmodia. • Symptoms subside, but can reoccur. • Transmitted to humans by mosquitoes • Females of genus Anopheles • Sexual reproduction takes place in the gut of the mosquito and the asexual phase occurs in the liver and blood of the human host.
