Chloroplast Origin and Evolution
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Questions and Answers

What is the main difference between the cyanelles of Cyanophora paradoxa and regular plastids found in higher plants?

  • Production of photosynthetic enzyme (correct)
  • Type of starch stored
  • Location of the nucleus
  • Presence of flagellated cells

    • Where are the cyanelles of Cyanophora paradoxa thought to be similar in evolution to?

  • Chloroplasts (correct)
  • Glaucocystis
  • Cyanobacteria
  • Red algae

    • What is the unique characteristic of the ecological niche that the first red alga likely evolved into?

  • Low oxygen levels
  • High temperature
  • Low pH (correct)
  • High salinity

    • What is the main difference between the Rhodophyceae and other algal classes?

    <p>Absence of flagellated cells</p> Signup and view all the answers

    What is the characteristic of the thylakoids in the chloroplasts of Rhodophyceae?

    <p>They occur singly</p> Signup and view all the answers

    Who first proposed the endosymbiotic origin of chloroplasts?

    <p>Konstantin Mereschkowsky</p> Signup and view all the answers

    What is the main characteristic of the larger species of fleshy red algae?

    <p>They occur in cool-temperate areas</p> Signup and view all the answers

    What did Mereschkowsky liken plastids to in his theory?

    <p>Little green slaves</p> Signup and view all the answers

    What has reinforced Mereschkowsky's theory of endosymbiotic origin of plastids?

    <p>Cytological and biochemical studies</p> Signup and view all the answers

    What is the approximate number of species of Rhodophyceae?

    <p>4000</p> Signup and view all the answers

    What has shown the similarity between cyanobacteria and plastids?

    <p>Nucleotide sequencing</p> Signup and view all the answers

    What is the characteristic of the Rhodophyceae that allows them to live at greater depths in the ocean?

    <p>Unique adaptation to low light conditions</p> Signup and view all the answers

    What is thought to represent intermediates in the evolution of the chloroplast?

    <p>Glaucophyta</p> Signup and view all the answers

    What was the likely outcome of the mutation that allowed the cyanobacterium to survive in the host flagellate?

    <p>The cyanobacterium secreted metabolites to the host flagellate</p> Signup and view all the answers

    What is unique about the symbiotic association in Glaucophyta?

    <p>The cyanobacterium is in the cytoplasm instead of a chloroplast</p> Signup and view all the answers

    What is the likely reason for the cyanobacterium's increased secretion of metabolites to the host flagellate?

    <p>The cyanobacterium lacked feedback inhibition</p> Signup and view all the answers

    Where does the fusion of one male nucleus and the carpogonial nucleus occur?

    <p>In the basal portion of the carpogonium</p> Signup and view all the answers

    What is the result of fertilization in the carpogonial branch?

    <p>Production of carpospores</p> Signup and view all the answers

    What is the function of the trichogyne in the reproductive process of red algae?

    <p>To facilitate contact with a spermatium</p> Signup and view all the answers

    What is the characteristic of the cell wall in the carpogonium after fertilization?

    <p>It becomes thicker</p> Signup and view all the answers

    What is the arrangement of tetraspores in a tetrasporangium?

    <p>All of the above</p> Signup and view all the answers

    What is the function of dictyosomes in the formation of tetraspores?

    <p>To lay down a wall inside the tetrasporangium</p> Signup and view all the answers

    What is the characteristic of spores in red algae?

    <p>They are motile by gliding</p> Signup and view all the answers

    How many classes are there in the Rhodophyta?

    <p>One</p> Signup and view all the answers

    What is the main difference between carrageenan and agar?

    <p>Carrageenan requires higher concentrations to form gels than agar</p> Signup and view all the answers

    What is the role of potassium ions in the formation of carrageenan gels?

    <p>They are required for the formation of gels</p> Signup and view all the answers

    What is the main use of carrageenans in the dairy industry?

    <p>As a stabilizer in milk and dairy products</p> Signup and view all the answers

    What is the advantage of carrageenans in instant puddings, sauces, and creams?

    <p>They do not require refrigeration to set</p> Signup and view all the answers

    What is the function of spermatia in the sexual reproduction of red algae?

    <p>They are the male gametes that are carried passively by water currents</p> Signup and view all the answers

    What is the difference between carpospores and tetraspores?

    <p>Tetraspores are generally larger than carpospores</p> Signup and view all the answers

    What is the function of gonimoblast filaments in the sexual reproduction of red algae?

    <p>They form the carposporangia and produce the diploid carpospores</p> Signup and view all the answers

    What is a property of carrageenans that makes them useful in pharmaceutical applications?

    <p>They inhibit human immunodeficiency virus (HIV) replication</p> Signup and view all the answers

    What is the characteristic of the thalli of Red Algae in intertidal or shallow subtidal environments?

    <p>They are delicate and thread-like</p> Signup and view all the answers

    Which pigments are responsible for the red coloration of Red Algae?

    <p>Phycoerythrin and phycocyanin</p> Signup and view all the answers

    What is the characteristic of the morphology of Red Algae in Order Batrachospermales?

    <p>Filamentous or branched</p> Signup and view all the answers

    Where are Red Algae in Order Nemaliales typically found?

    <p>In marine environments, particularly in intertidal and subtidal regions</p> Signup and view all the answers

    What is the characteristic of the thalli of Red Algae in Order Corallinales?

    <p>Calcified with calcium carbonate deposits</p> Signup and view all the answers

    What is the characteristic of the reproduction of Red Algae?

    <p>Either sexually or asexually by spores or filament fragmentation</p> Signup and view all the answers

    What is the characteristic of the color of Red Algae in Order Corallinales?

    <p>Red, pink, purple, yellow, or blue</p> Signup and view all the answers

    Where are Red Algae in Order Corallinales typically attached to?

    <p>Hard substrates such as rocks, shells, or coral reefs</p> Signup and view all the answers

    Study Notes

    Endosymbiotic Origin of Chloroplasts

    • Konstantin Mereschkowsky proposed the endosymbiotic origin of chloroplasts in 1905.
    • He likened plastids to "little green slaves" working for their host cells to produce food from sunshine.
    • Nucleotide sequencing has shown the similarity between cyanobacteria and plastids, supporting the endosymbiotic origin theory.
    • All plastids evolved from a single endosymbiotic event.

    Evolution of Chloroplasts

    • A cyanobacterium was taken up by a phagocytic organism into a food vesicle, leading to an endosymbiotic relationship.
    • The cyanobacterium evolved into a chloroplast surrounded by two membranes of the chloroplast envelope.

    Glaucophyta

    • Glaucophyta includes algae that have endosymbiotic cyanobacteria in their cytoplasm instead of chloroplasts.
    • They are thought to represent intermediates in the evolution of chloroplasts.
    • The cyanelles of Cyanophora paradoxa are similar to chloroplasts in evolution, but are primitive in regard to where photosynthetic enzymes are produced.

    Rhodophyta

    • Rhodophyta is a division of red algae that comprises the class Rhodophyceae.
    • Rhodophyceae are probably one of the oldest groups of eukaryotic algae.
    • They are directly descended from a cyanome in the Glaucophyta.
    • The first red alga likely evolved into an ecological niche unoccupied by cyanobacteria, in waters with a pH less than 5.

    Characteristics of Rhodophyceae

    • Lack flagellated cells
    • Have chlorophyll a, phycobiliproteins, Floridian starch as a storage product, and thylakoids occurring singly in the chloroplast
    • Most species are found in marine environments, particularly in intertidal zones
    • Reproduce sexually and asexually by spores or filament fragmentation

    Carrageenan

    • Carrageenan is a phycocolloid similar to agar but with a higher ash content and requiring higher concentrations to form gels.
    • It is obtained from wild populations of Irish moss and is used extensively for many purposes, including stabilizing emulsions and stiffening milk and dairy products.

    Red Algae Reproduction

    • In sexual reproduction, gamete cells have no flagella and spermatia are carried passively by water currents to the female organ, the carpogonium.
    • Fertilization stimulates the production of polyamine spermine, which steers the carpogonial branch toward the production of carpospores.
    • Tetrasporangia form four tetra spores, either in a row, crosswise, or in a tetrad.

    Asexual Spores

    • Monosporangia and parasporangia produce asexual spores that re-form the parent thallus.
    • Spores, whether monospores, tetraspores, or carpospores, of almost all red algae are capable of motility by gliding.

    Red Algae Classification

    • Rhodophyta has a single class, the Rhodophyceae.
    • The Rhodophyceae was previously divided into two subclasses, the Bangiophycidae and the Florideophycidae.
    • There are several orders of red algae, including Batrachospermales, Nemaliales, and Corallinales, each with distinct characteristics.

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    Description

    Learn about the endosymbiotic origin of chloroplasts, first proposed by Konstantin Mereschkowsky. Discover how plastids work with host cells to produce food from sunlight.

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