Protozoans – The Animal-like Protists

Animal-like Protists Unicellular Consumers Usually produce asexually, but may also produce sexually. Live in or on other living or dead organisms that are found in soil or water. Many have specialized vacuoles for digesting food and getting rid of excess water.

Importance of Protozoans Serve as a food source for larger organisms. Shells of protozoans become part of the sediment (and later rock) and can be an indicator for petroleum. Many protozoans cause disease in tropical areas. Examples: Giardia and Malaria

Classification of Protozoans Classified by how they move. Ciliates (phylum Ciliophora) Flagellates (phylum Zoomastigina) Amoebas (phylum Rhizopodia) Sporozoans (phylum Sporozoa)

Ciliates Have cilia. Live in aquatic environments. Cilia are short, threadlike structures that extend from the cell membrane. Cilia beat in a coordinated way to move the organism in any direction. Live in aquatic environments. Include the most complex and the largest one celled protists.

Ciliates Structure of ciliates: 2 nuclei Macronucleus Micronucleus Controls: feeding exchange of carbon dioxide and oxygen amount of water and salts entering and leaving the ciliate. Micronucleus Involved in reproduction. Ciliates usually reproduce asexually by dividing crosswise to produce two daughter cells. Paramecium join and exchange genetic information and then separate and divide asexually when environmental conditions become unfavorable.

Ciliates Structure of ciliates Oral groove Contractile vacuole Similar to a mouth. Food is swept into the oral groove and then surrounded by a vacuole. Wastes are moved out of the ciliate through the anal pore. Contractile vacuole Only found in freshwater ciliates. Ejects water from the cell when it contracts.

Flagellates Have flagella. Many live in freshwater. May be parasites or may be helpful to other organisms. Can live in colonies where each organism performs a specific function.

Amoebas Move and feed by utilizing pseudopodia. A psuedopod is a temporary extension of the cytoplasm. The cytoplasm surrounds the food particle and then breaks off to form a vacuole. May live in freshwater, saltwater or moist areas. Freshwater amoebas have contractile vacuoles. Can be parasites.

Amoebas Reproduce asexually. A single parent produces one or more identical offspring by dividing into two cells. Some may form cysts that can survive extreme conditions. Some amoebas will secrete a shell around their cell (Foraminiferans, Radiolarians). Some of these shells have holes through which the psuedopod can extend.

Sporozoans Have complex life cycles with both sexual and asexual reproduction. Most produce spores, a reproductive cell that forms without fertilization and produces a new organism. All live as internal parasites in one or more hosts, usually in the blood or intestines. Cannot move on their own.