Transcript ppt
Protozoa II Support and Locomotion Locomotion depends on interactions between cell surface & surrounding medium Protozoa were originally classified according to how they move. Locomotion Flagella Cilia Pseudopods Some are non-motile How Do Protists Move? • Pseudopods • Flagella – long, whip-like “hairs” • Cilia – short, fine “hairs” • Some are non-motile Pseudopodia Lobopodia Chaos, Arcella Filopodia Difflugia Reticulopodia Foraminiferans Axopodia or Actinopodia Actinosphaerium, Radiolarians Hyaline cap Chaos Arcella Lobopoda Lobopodia Difflugia Foraminiferans Reticulopodia: Bidirectional cytoplasmic streaming Actinosphaerium Radiolarians Actinosphaerium Axopodia: Bidirectional cytoplasmic streaming Climacostomum Rows of kinetosomes (basal bodies) Dynine arms have ATPase activity When dynine arms use ATP, microtubule doublets slide past each other When microtubules slide past each other the flagella changes shape Cilia Movement Power Stroke Recovery Stroke Tetrahymena pyriformis Conchothirus membranelle Cilia in adjacent rows lean towards each other Basal body cirrus Stylonychia membranelles Undulating membrane Flattened sheet of cilia Stylonychia Ciliate Pellicle with Alveoli Ca ++ storage Defense Flagellar Movement metaboly Metaboly Astasia Euglenophyte Swimming Swim by one or two flagella; only the tip of flagellum is moving, propelling the cell forward Light sensing system: 2 major parts, paraflagellar rod at the base of at least the emergant flagellum; contains light-sensitive flavins Eye-spot (stigma): in the cytoplasm adjacent to the ampulla; bright orange by carotenoids Light direction: the eye-spot shades the paraflagellar body while cell is swimming in rotating movements along its axis Positive phototaxis: most phototrophic euglenophytes swim towards the light source Chlamydomonas reinhardtii. Eyespot/cv/chloroplast Tinsel Flagella (Flimmergeisel) Myonemes – “muscle-like” Myonemes – “muscle-like” Myonemes – “muscle-like” myonemes (protein that plays a major role in the formation of coated vesicles) Lysosome Nutrition Some are autotrophs Photosynthetic Chloroplasts Endosymbiotic algae Most are heterotrophs Saprobes (Saprozoic) - feed on dissolved organic molecules Decomposers Parasites of animals Holozoic - feed on particles Nutrition - Autotrophs Photosynthesis Photosynthetic protists & bacteria - dominant carbon producers in oceans and lakes. Nutrition - Autotrophs 3 key themes of the evolution of photosynthesis in protists: Different groups of algae can be distinguished by the photosynthetic pigments they contain. Different pigments absorb different wavelengths of light. Diversity in pigments lets different types of algae inhabiting the same area to absorb different components of available light. So different types of algae live at different depths. Absorptive Feeding Physarum sp. Entamoeba histolytica – traveler’s diarrhea Nutrition Absorptive feeding Some protists are decomposers and feed on detritus (dead organic matter). Secrete enzymes to breakdown organic molecules Absorb these smaller molecules through cell membrane Parasitic protists absorb their food inside a living host, and may damage the host. Nutrition Holozic or Ingestive feeding May ingest particulate detritus Many protists are large enough to engulf bacteria & other protists, by phagocytosis. These predators are referred to as raptorial. Phagocytotic protists lack cell walls and have flexible membranes and cytoskeletons that they can use to surround potential food sources. These innovations allow them to eat other cells instead of competing with them for food or sunlight. Feeding & Excretion Phagocytosis Feeding & Excretion Phagocytosis Feeding & Excretion Phagocytosis Feeding & Excretion Exocytosis Feeding & Excretion Exocytosis Feeding & Excretion Exocytosis Feeding & Excretion Exocytosis Feeding & Excretion Exocytosis Holozoic protists obtain food in a variety of ways: Active predators hunt down their food by moving through their habitat and engulfing their prey. Ambush predators sit and wait for prey to come by, or have cilia that move the environment past them. Filter feeders collect food by sweeping water into their mouth usually using cilia. Food Vacuoles/ Phagosomes Paramecium food vac cytoproct Reproduction Highly variable Often very complex Asexual binary fission produces 2 equal daughter cells budding produces unequal daughter cells schizogony produces multiple equal daughter cells Reproduction Binary fission (mitosis) asexual reproduction- the cell divides into two Genetic recombination Conjugation (ciliate sex) see Brusca p. 143 Two cells exchange copies of their micronuclei, leading to genetic recombination Binary Fission Mother cell Daughter cells Sexual Reproduction Involves meiosis Production of gametes Isogametes - same size gametes Anisogametes - gametes different size, appearance Fertilization Syngamy = fusion of gametes Union of haploid gametes to produce diploid zygote Source of genetic variation Sexual Reproduction Conjugation is sexual reproduction without gametes Conjugating micronuclei cells exchange haploid Autogamy Necessary for long-term survival of ciliates Reorganization of genes in macronucleus Similar to preliminary steps for conjugation New Genotypes may be formed so this is a source of genetic variation w/o sexual reproduction Ciliophora Dimorphic nuclei Heterokaryotic • Macronucleus = multiple dispersed copies of genomeused for transcription. • Micronuclei (one or more) = condensed* copies of genomeused for replication and conjugation. *what does this mean? Conjugation Figure 03_18 Binary fission in Stentor coeruleus Autogamy– nuclear reorganization Necessary for long-term survival of ciliates Reorganization of genes in macronucleus 7 nuclei disintegrate, get one remaining haploid micronucleus that undergoes mitosis to give 2 micronuclei which then fuse m M M M Animals Many Algae Plants Alternation of Generations Unnumbered table 03_01 Go over Research Focus Box 3.1; explain experiments. What is phenotypic plasticity? Protozoan Diversity Go to “Protozoa” in Lab Stuff