chapter 20 outline
chapter 20 outline BIOL 1110
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This 4 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 13 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
Protists and the Origin of Eukaryotic Cells 20.1 Defining protists, their evolutionary importance, and habitats Protists Not included in plant, fungal, animal kingdoms o Differences in structural & reproductive features and DNA sequence info Often microscopic Most abundant in moist habitats Algae – generally contain 1 or more plastids; photosynthetic (autotrophic) or have photosynthetic relatives Protozoa –non-photosynthetic & lack plastids (heterotrophic) o Some ingest algal cells that function like plastids providing organic food Fungus-like protists also lack plastids and photosynthesis Streptophyte green algae – most closely related to land plants o Streptophytes – land plants and closest algal relatives Land plants – embryophytes (contain embryo) Bodies may be 1. Unicellular 2. Aggregates (colonies) 3. Filaments 4. Tissues whose cells communicate chemically (specialized) Mulitcellularity – key to origin of land plant, fungal, animal kingdoms Common and numerous in aquatic/moist habitats Symbiosis – intimate ecological association between two or more organisms o Mutualism – both benefit o Endosymbionts live within bodies Can inactively (no metabolic/reproductive actions) survive in dry conditions until moisture becomes available Flagella o Eukaryotes – long, propelling extensions from cells; contain microtubules and motor proteins; rapidly bend and straighten o Prokaryotes – spin like propellers; flagellates depend on flagella Cilia – similar inside but are shorter and more abundant; more power; descended from common ancestor Amoebae move by extending cytoplasm into cellular lobes and flowing rest of cytoplasm in same direction; slower 20.2 Protists can be classified into eukaryotic supergroups Stramenopile algae – many types of autotrophic algae that are classified with stramenopiles o Plastids include chlorophyll and large amounts of gold or brown pigments o Include silica-walled diatoms o Brown algae – kelps that form forests harboring marine life o Strawlike hairs on longer flagella o Heterokonts – different structured flagella o Oomycetes – heterotrophic protists; fungus-like; some are parasites (Phytophthora – crop diseases) Green algae – many are flagellate or have flagellate reproductive stages o Freshwaters, ocean, or land o Primary color – chlorophyll o Cells store starch in plastids o Streptophyte green algae – cellulose-rich walls, cytokinesis – production of plasmodesmata, sexual reproduction; ancestors of land plants Red algae – no flagella 20.3 Algal diversity reflects the occurrence of key evolutionary events Eukaryotes Nucleus and endomembrane system o Formed by infolding of cell membrane Originated from Archaea Phagotrophy – acquiring food through endocytosis; first step by which mitochondria and plastids originated by endosymbiosis o Mitochondria – present in early protists; ingested but not digested by endocytosis endosymbionts; genetic info eventually moved to nucleus Proteobacterial endosymbionts – retained because benefitted host with ATP harvest from organic food (example: Krebs cycle, electron transport, oxidative phosphorylation in mitochondria) Primary protists – double membrane; secondary/tertiary protists – more than two membranes 20.4 Protist reproductive diversity Asexual All protists do this by mitotic division Genetically identical offspring many chances to survive conditions Spores – single-celled reproductive structures often produced by protists; released and dispersed throughout environment from parent to decrease competition o Zoospores – flagellate asexual reproductive cells swim through water films Sexual Advantage: diverse genotypes faster evolutionary response to environment Zygotic – common among protists and fungi o Green algae o Most cells are haploid; only single-celled zygotes are diploid Sporic – alternation of generations o Brown algae o Both stages are multicellular o Sporophytes produce spores; grow into gametophytes; diploid; dominant o Gametophytes produce gametes; resulting zygote grows by mitosis; haploid Gametic o Only gametes are haploid o Advantage: most cells have spare set of genes o Sporophyte-dominant gametophytes are virtually absent (except gametes) Oogamy – retention of egg on gametophyte Chapter Wrap-up Examine and Discuss Self Test 1. Discuss the difference between heterotrophs and autotrophs and provide several protist examples of each. 2. Algae as a group exhibit a diverse array of body forms. Name and describe some of the more common algal body forms. 3. Distinguish between a sporophyte and a gametophyte. What kinds of algae produce both of these life cycle stages and what kinds produce only one or the other? 4. Explain why brown, red, and green algae differ in color. What photosynthetic pigment occurs in all photosynthetic algae (as well as photosynthetic, oxygen-producing cyanobacteria and plants)? 5. Discuss the ecological importance of algae, starting with their impact on Earth’s atmosphere. 6. Describe some of the economic uses of algae. Applying Concepts 1. New species of algae are continuously being discovered, but some are so small that it can be difficult to distinguish them from close relatives. What characteristics and methods might be used to determine a new alga’s relationships? Devise a strategy that starts with low-cost procedures and utilizes higher-cost procedures only if necessary. 2. What are the advantages of being a single-celled protist? What are the disadvantages? How might a single-celled protist overcome the disadvantages? 3. What are the advantages of being multicellular seaweed? What are the disadvantages? How can seaweeds overcome the disadvantages? 4. What are the advantages of being a photosynthetic (autotrophic) protist and what are the disadvantages? 5. What are the advantages of being a heterotrophic protist and what are the disadvantages?
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