CONCEPT 28.4 ALVEOLATES HAVE SACS BENEATH THE PLASMA MEMBRANENamroo, Austin, Will
Table Of Contents Dinoflagellates Apicomplexans Ciliates
Intro Members of the clade Alevolata have alveoli, small membrane-bound cavities, under the plasma membrane. Their function is not known, but they may help stabilize the cell surface or regulate water and ion content. Alveolata includes flagellated protists (dinoflagellates), parasites (apicomplexans), and ciliates.
Dinoflagellates Dinoflagellates are abundant components of marine and freshwater phytoplankton. Dinoflagellates and other phytoplankton form the foundation of most marine and many freshwater food chains. Other species of dinoflagellates are heterotrophic. Most dinoflagellates are unicellular, but some are colonial.
Dinoflagellates Cont.. Dinoflagellate blooms, characterized by explosive population growth, can cause “red tides” in coastal waters. Toxins produced by some red-tide organisms have produced massive invertebrate and fish kills. These toxins can be deadly to humans as well. Some dinoflagellates form mutualistic symbioses with coral polyps, the animals that build coral reefs.
Ampicomplexans What are they? Sporozoites Apicoplasts Have sexual and asexual stages Plasmodium, Anopheles mosquitoes, and malaria…
Ciliates Ciliates- protists who use cilia to move and feed. Completely cover the cell surface or may be clustered in a few rows or tufts. A distinctive feature of ciliates is that there are two types of nuclei. Large macronuclei – feeding, waste removal, water balance Tiny micronuclei A cell may have more than one nucleus of each type.
Feeding, Waste Removal, Water Balance Paramecium, like other freshwaterFEEDING, WASTE REMOVAL, AND WATER BALANCE protists, constantly takes in water by osmosis from the hypotonic Contractile Vacuole Paramecium feeds mainly on bacteria. environment. Rows of cilia along a funnel-shaped oral Bladderlike contractile vacuoles groove move food into the cell mouth, accumulate where the food is engulfed into food excess water from radial canals and vacuoles by phagocytosis. periodically Oral grooveexpel it through the plasma membrane. Cell mouth50 µm Thousands of cilia cover Food vacuoles combine with the surface of Paramecium. lysosomes. As the food is digested, the vacuoles follow a looping path Micronucleus through the cell. Macronucleus The undigested contents of food vacuoles are released when the vacuoles fuse with a specialized region of the plasma membrane Figure 28.12 that functions as an anal pore.
Reproduction and Conjugation Ciliates reproduce asexually by binary fission Conjugation causes genetic variation. A sexual process in which the two individuals exchange haploid micronuclei.
CONJUGATION AND REPRODUCTION Two cells of compatible 2 Meiosis of micronuclei 1 mating strains align side 2 produces four haploid 3 Three micronuclei in each cell disintegrate. The remaining micr by side and partially fuse. micronuclei in each cell. nucleus in each cell divides by mi MEIOSIS 4 The cells swap one micronucleus. Macronucleus Haploid Compatible Diploid micronucleus mates micronucleus Diploid micronucleus MICRONUCLEAR FUSION 5 The cells separate. Two rounds of cytokinesis The original macro- Three rounds of9 8 nucleus disintegrates. 7 mitosis without 7 6 Micronuclei fuse, partition one macronucleus 8 forming a diploid Four micronuclei cytokinesis Key and one micronucleus micronucleus. become macronuclei, into each of four daughter cells. produce eight Conjugation while the other four micronuclei. Reproduction remain micronuclei.