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Ch 26 The origins of Eukaryotic

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Ch 26 The origins of Eukaryotic Powered By Docstoc
					56f84e70-e7a6-4ff3-b510-eb644a4cedd5.rtf                                           9/23/00                             1
Ch 28 The origins of Eukaryotic Diversity
Lecture notes:
Using a microscope that he made himself, Anton von Leeuwenhoek (17 th century) was the first to describe the diversity
of microscopic protists

Their are about 60,000 extant species of protists most are unicellular, but some colonial and simple multicellular forms
exist

Eukaryotic structure makes even the simplest organism more complex than prokaryotes primal eukaryotes gave rise to
current protists, plants fungi and animals

1. Eukaryotes originated by symbiosis among prokaryotes
     A. A greater difference exists between prokaryote and eukaryote cells than between cells of plants and animals
     B. The unique structure that arose during the genesis of protists
         1. A membrane bound nucleus
         2. mitochondria, chloroplasts and the endomembrane system
         3. a cytoskeleton
         4. 9+2 flagella
         5. Multiple chromosomes consisting of linear DNA molecules compactly arranged with proteins
         6. diploid life cycle stages
         7. mitosis
         8. meiosis
         9. sex
     C. The limitations of a prokaryote are
         1. the number of metabolic activities that can occur at one time is limited by a small genome
         2. A small prokaryotic genome limits the number of genes which code for metabolic enzymes
     D. natural selection resulted in increasing complexity in some groups: these trends were
         1. Multicellular forms like cyanobacteria which have different cell types performing specialized functions
         2. evolution of complex bacterial communities where each species benefits from the metabolic activities of other
               species
         3. compartmentalization of different functions with single cells
               a. By definition this would be the first eukaryote

     E. The evolution of compartmentalized Eukaryotic cells may have resulted form two processes
         1. Specialization of plasma membrane invagination
              a. Invagination and subsequent specialization’s may have given rise to the nuclear envelope, endoplasmic
              reticulum, Golgi apparatus and other components of the endomembrane system
         2. Endosymbiotic associations of proks may have resulted in the appearance of some organelles
              a. mitochondria and chloroplasts evolved form prokaryotes living within other prokaryotic cells

     F. The Endosymbiotic theory proposes that certain prokaryotic species called endosymbionts lived within larger
proks.
     This theory was developed by Lynn Margulis
         1. Focuses mainly on mitochondria and chloroplasts (they are similar to bacteria)
         2. Chloroplasts are descended from cyanobacteria
         3. Mitochondria are descendants of prokaryotic aerobic Heterotrophs
              a. parasites or undigested prey of larger proks
              b. association progressed from parasitism or predation to mutualism
              c. as became more independent became one organism




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         4. many organisms currently are in an endosymbiotic relationship
     G. Evidence for endosymbiotic relationship includes
         1. Mitochondria and chloroplasts are of appropriate size to be descendants of eubacteria
         2. M & C have inner membranes consisting of several enzymes and transport systems that resemble prok plasma
                   membranes
         3. replicate by binary splitting process similar to proks.
         4. Contain their own tRNA, ribosome’s, and other components for DNA transcription and translation.
         5. Ribosome’s are more similar to prokaryotic DNA structures than euks

     H. Molecular systematics also supports endosymbiotic theory
        1. the rRNA of chloroplasts is more similar in base sequence to RNA from certain photosynthetic eubacteria than
              to rRNA in Eukaryotic cytoplasm
        2. Mitochondria also share similarities to eubacteria that suggest an origin with these groups.

     I. A comprehensive theory for the origin of Eukaryotic cells must also include the evolution of:
         1. 9+2 flagella and cilia which are analogous to prokaryotic flagella
         2. the origins of mitosis and meiosis which also utilize microtubules
               a. mitosis made it possible for large euk genomes to be reproduced
               b. meiosis is essential to sexual reproduction
               c. protists have the most varied sexual life histories of the euks

2. Archezoans provide clues to the early evolution of eukaryotes
     A. The archezoa branched away from the Eukaryotic tree very early.
         1. lack mitochondria and plastids, simple cytoskeletons
         2. ribosomes have some characteristics aligned with prokaryotes and less similar to eukaryotes
               a. rRNA sequencing has strengthened this relationship
     B. Giardia intestinalis is a modern representative of archezoa
         1. Flagellated unicellular Eukaryotic that is parasitic in human intestine
         2. transmitted as a cyst from water contaminated with human feces
     C. Giardia's importance to evolutionary biologists is related            more to its characteristics than to its role as a
human           parasite
         1. Diplomonads have two separate haploid nuclei which produce "Face-like" appearance
               a. The dual nuclei may be a vestige of early Eukaryotic evolution
         2. Proks have haploid geneomes and some researchers postulate that early eukaryotes had a single haploid
nucleus        bounded by a nuclear envelope
         3. In most modern euks the diploid stages in the life cycle result from the fusion of haploid nuclei which form the
         diploid nucleus
               a. Diplomonads may represent an early mechanism in the evolution of diploidy in eukaryotes
     D. If the diplomonads diverged from the Eukaryotic lineage before the process of nuclear fusion and meiosis evolved
     their dual nuclei may be a clue to the past
         1. This coupled with the absence of mitochondria in this group and other archezoans is consistent with than origin
               occurring before the endosymbiotic relationships that gave rise to mitochondria in aerobic species

3. The diversity of protists represents different "experiments" in the evolution of Eukaryotic organization
     A. Precambrian rock of 21.Billion years of age contain fossils of acritarchs the oldest fossils of protists
         1. The fossilized remnants are of cysts
         2. adaptive radiation produced a diversity of protists over the next billion years
         3. variations present are representative of the structure and function possible in Eukaryotic cells
     B. Protists are found in all moist environments
         1) They are important components of marine and freshwater plankton = communities of organisms that drift




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               passively or swim weakly near the surface of oceans ponds and lakes
         2)    can also be bottom dwellers living in sand and silt
         3)    photosynthetic species form mats at still water edges of lakes and other bodies of water,
         4)    Damp soil, litter and moist terrestrial habitats also contain large numbers of protists
         5)    symbiotic species are found in the body fluids, tissues and cells of the host
               a) these associations range form parasitism to mutualism
     C. Most are aerobic, using mitochondria for cellular respiration
         1) Anaerobic forms lack mitochondria and live in anaerobic environments or have mutualistic respiring
               bacteria
         2) Have many forms of nutrition, photoautotrophic, heterotrophic or mixotrophic
         3) Most have flagella or cilia at some point in their life cycle (not similar to proks)
               a) Euk cilia and flagella re extensions of the cytoplasm
               b) Cilia and flagella have basic 9+2 structure
               c) are shorter and more numerous
     D. Cell division and nuclear structure are very variable in the protists
         1. unique mitotic divisions occur in many groups
         2. all can reproduce asexually, can reproduce sexually or use syngamy to trade genes between asexual
                reproductive episodes
         3. They form resistant cysts when stressed by harsh environments
     B. Protists are considered the simplest Eukaryotic organisms              because most are unicellular
         1. at a cellular level protists are extremely complex
         2. the unicellular protist is not analogous to a single plant or animal cell, but a complex organism
                a. The single cell of a protist must perform all the basic functions carried out by the specialized cells of
plants              and animals

4. Protistan taxonomy is in a state of flux.
     A. Classification schemes and phylogeny are based on available information which is incomplete
          1. The system presented here are not permanent and will change as more information becomes available
     B. 1969 Robert H. Whittaker popularized the 5 kingdom taxonomic system and placed only unicellular eukaryotes
      in the kingdom protista
          1. 1970's and 80's protista is expanded to include some multicellular organisms
          2. studies of cell ultrastructure and life cycle details formed the basis for such taxonomic transfers
                a. Seaweeds have characteristics that make them closer to algae than to plants
                b. slime molds and water molds found to be more closely related to certain protozoans than to fungi
          3. Was used as a junk place to fit euks that did not fit comfortably any place else

     C. Molecular systematics, rRNA comparisons have stimulated 3 main trends in Eukaryotic systematics and taxonomy
     over the last decade
         1. reassessment of the number and membership of protistan phyla
               a. the phylum Sarcodina once held all organisms that had pseudopodia, current classification splits these
               organisms into several phyla
         2. Arrangement of the phyla into a cladogram based largely on molecular methods and cell structure
     comparisons reveal evolutionary relationships of protists
         3. reevaluation of the five kingdom system and debate about the addition of new kingdoms
               a. the kingdom archezoa has been proposed as well as other kingdoms for forms previously classified as
               protists
     D. The proposal of additional kingdoms challenges the current view of biological diversity at the highest taxonomic
     levels

5. Diverse modes of locomotion and feeding evolved among protozoa




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     A. protozoa is an informal reference to a very diverse group of heterotrophic protists
         1. These organisms seek and consume bacteria, other protists and detritus
         2. are symbiotic and many are pathogens
         3. the subdivision of this group into different phyla is based in part on how they feed and move
         4. as protistan systematics continues to be reevaluated some of the following phyla may be split or combined.

6. Rhizopodia (Amoebas)
     A. the phylum Rhizopoda (rootlike feet) include the amoebas and their relatives
         1. simplest of protists: are all unicellular
         2. no flagellated stages in life cycle
         3. Pseudopodia cellular extensions and function in feeding and movement
               a. The cytoskeleton of microtubules and microfilaments functions in amoeboid movement
         4. All reproduction is by asexual mechanisms: no meiosis or sexual reproduction are known to occur
         5. during mitosis, spindle fibers form, but typical stages of mitosis are not apparent in most species
               a. the nuclear envelope persists during cell division in many genera
               b. Rhizopods inhabit freshwater, marine and soil habitats
               c. most are free living although some are parasitic

     B. Actinopoda (Heliozoans and Ridiozoans)

         1) Actinopods (ray feet) posses Axopodia a slender for of pseudopodia Axopodia = projection reinforced by
              bundles of microtubules thinly covered by cytoplasm
         1. Axopodia increase the surface area that comes into contact with the surrounding water.
              a. helps the organisms float and function in feeding
              b. small protists and other microorganisms which stick to the axopodia are phagocytized by the thin layer
of            cytoplasm and moved to the main portion at the cell by cytoplasmic streaming
         2. The main groups of Actinopoda are the Heliozoans and the radiozoans
              a. post are planktonic
              b. heliozoans live primarily in fresh water
              c. Radiozoans are primarily marine and have delicate shells usually made of silica

      C. Foraminifers (Forams)
          1. Forams have porous, multi chambered shells of organic material hardened by calcium carbonate
               a. forams are exclusively marine with most living in the sand or attached to algae and rocks: some are
planktonic
               b. cytoplasmic strands extend through the shell's pores and function in swimming, feeding and shell
formation
               c. many have symbiotic algae living beneath the shell which provide nourishment through photosynthesis
               d. 90% of the described species are fossils
               e. foram shells are an important component of sediments and sedimentary rocks
      D. Apicomplexa (Sporozoans)
          1. All species of the phylum Apicomplexa are parasites of animals
               a. The infectious cells produced in the life cycle are       called sporozoites
               b. the apex of sporozoites has organelles for penetrating host cells and tissues, it gives this phylum its name
               c. live cycles are intricate having both sexual and asexual reproduction: often requiring two or more
different           host species
          2. Several species of Plasmodium cause malaria
               a. Anopheles mosquitoes serve as the intermediate host and humans as the final host
               b. The incidence of malaria was greatly reduced by the use of insecticides against mosquitoes in the 60's
               c. More recently incidence of malaria has increased due to insecticide resistant strains of mosquitoes and




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               drug resistant strains of Plasmodium
                    (1) relatively common resulting in 3 million deaths a year
         3. Little success in developing vaccine against Plasmodium
               a. Human immune system has little effect on the parasite
                    (1) Plasmodium spends most of its life cycle in blood cells or liver cells (away from immunity)
                    (2) Plasmodium has the ability to alter its surface proteins, so the body cannot target it
               b. The most promising vaccine is a mixture of synthetic proteins which mimic several Plasmodium
                    membrane proteins.

     E. Zoomastigophora (Zooflagellates)
         1. All species are Heterotrophs
               a. use whip like flagella to move
               b. most are solitary but some are colonial
               c. most free living but some are symbiotic
                    (1) symbionts inhabit the gut of termites and digest cellulose
         2. species Trypanosoma cause African sleeping sickness and are spread by the bite of the tsetse fly
               a. large natural reservoir, many African mammals harbor the parasite
               b. can alter their coat proteins to evade immunology
         3. are closely related to other flagellated protists including Euglena

     F. Ciliophora (ciliates)
         1. use cilia to move and feed
               a. Most exist as solitary cells in fresh water
               b. cilia are short and beat in synchrony
               c. cilia are associated with a submembranous system that coordinates the movement of thousands of cilia
               d. cilia can be dispersed over surface or clustered in fewer rows of tufts
               e. some move on leg like Cirri (many cilia bounded together)
               f. other species have rows of tightly packed cilia that function together as locomotor membranells
         2. Ciliates possess two type of nuclei: one large macronucleus and form one to several small micronuclei
               a. Characteristics of macronucleus
                    (1) it is large and has over 50 copies of the genome
                    (2) genes are packaged in a large number of small units, each with hundreds of copies of just a few
genes
                    (3) it controls everyday functions of the cell by         synthesizing RNA
                    (4) it is also necessary for asexual reproduction during binary fission. The macronucleus elongates and
                           splits instead of undergoing mitosis
               b. Characteristics of the micronucleus
                    (1) it is small and may number form 1 to 80 micronuclei,             depending on the species
                    (2) it does not function in growth, maintenance or asexual reproduction
                    (3) functions in conjugation, a sexual process which produces genetic variation
               c. Note that meiosis and syngamy are separate form reproduction

7. Fungus like protists have morphological adaptations and life cycles that enhance their ecological role as
decomposers
    A. The resemblance of slime molds, water molds and true molds is a result of convergent evolution of filamentous
    body structure
        1. filamentous body structure increases exposure to the environment and enhances their roles as decomposers
        2. slime molds differ form fungi in their cellular      organization, reproduction and life cycles
               a. slime molds are more closely related to amoeboid protists than to true fungi
        3. Molecular comparisons indicate water molds are related to certain algae although they lack chloroplasts




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        B. Myxomycota (Plasmodial Slime Molds)
            1. Myxomycota consists of plasmodial slime molds which are all Heterotrophs and many are brightly pigmented
            2. Plasmodium = feeding stage of life cycle consisting of an amoeboid, coenocytic (multinucleated cytoplasm
            undivided by membranes) mass.
                  a. In most species, the nuclei of plasmodia are diploid and exhibit synchronous mitotic divisions
                  b. cytoplasmic streaming within the plasmodium helps distribute nutrients and oxygen
                  c. engulfs food by phagocytosis as it grows by extending pseudopodia
                  d. live in moist soil, leaf mulch and rotting logs
                  e. When stressed by drying or lack of food, the plasmodium ceases growth and forms sexually reproductive
                  structures called fruiting bodies, or sporangia
        C. Acrasiomycota (Cellular Slime Molds)
            1. The phylum Acrasiomycota includes the cellular slime molds
                  a. Feeding stage of life cycle consists of individual,       solitary haploid cells
                  b. When the food supply is depleted, cells aggregate to form a mass similar to those of myxomycota but
cells
                  remain separate (not coenocytic)
                 c. Fruiting bodies function in asexual reproduction (unlike plasmodial slime molds).
                 d. only a few have flagellated stages

        D. OOmycota
            1. The phylum OOmycota includes water molds, white rusts, and downy mildews.
                  a. have coenocytic hyphae (fine, branching filaments) that are analogous to fungal hyphae
                  b. cell walls are made of cellulose rather than the chitin found in true fungi
                  c. diploid condition in the life cycle prevails in most species
                  d. biflagellated cells are present in the life cycles, while fungi lack flagellated cells
            2. In water molds
                  a. large egg is fertilized by a smaller sperm cell to form a resistant zygote
                  b. these organisms are usually decomposers which grow on dead algae and animals in fresh water
                  c. some are parasitic, growing on injured tissue but may also grow on skin and gills of fish
            3. White rusts and downy mildews:
                  a. are usually parasitic on terrestrial plants
                  b. disperse by windblown spores but also form flagellated zoospores at some point in their life cycle
                  c. some of the most important plant pathogens are members of this phylum

8. Eukaryotic algae are key producers in most aquatic ecosystems
     A majority of the Eukaryotic algae are photosynthetic with only a few of the phyla having heterotrophic or
mixotrophic members
         1. Algae = relatively simple photoautotrophic aquatic organisms
         2. these organisms were classified in the kingdom protista in the 5 kingdom system
         3. are of great ecological significance
         4. account for 50% of global photosynthetic production of organic material
         5. forms include fresh water plankton, marine plankton and intertidal seaweeds that form the basis of aquatic food
               webs
     A. All algae have chlorophyll a like plants. The phylogenetic relationships among algal phyla have been determined
by differences in
         1. accessory pigments such as carotenoids, xanthophylls, phycobilins and other forms of chlorophyll
         2. chloroplast structure
         3. cell wall chemistry
         4. number an type of position of flagella
         5. food storage product




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      B. Dinoglagellata (Dinoflagellates)
          1. Dinoflagellates are components of phytoplankton which provides the foundation of marine food chains
          2. may cause a red tides by blooms
                a. dinoflagellates produce a toxin that is concentrated by invertebrates including shellfish
                b. the toxin is dangerous to humans consuming shellfish and causes the condition known as paralytic
shellfish            poisoning
          3. Most are unicellular, some are colonial
          4. Cell surface is reinforce by cellulose plates with flagella in perpendicular groves, creating its whirling
                movements resulting in a characteristic shape
          5. some live as photosynthetic symbionts of the cnidarians that build coral reefs
          6. some lack chloroplasts and live as parasites, few carnivores
          7. have brownish plastids containing chlorophyll a, chlorophyll c and a mix of carotenoids including peridinin
      (only in this phylum)
          8. food is stored as starch
          9. chromosomes lack histones and are always condensed
          10. has not mitotic stages
          11. kinetochores are attached to the nuclear envelope and chromosomes distributed to daughter cells by splitting
          of the nucleus

         Dinoflagellates are probably more closely related to zooflagellates than to any phylum of the algae
     C. Bacillariophyta (Diatoms)
         1. The phylum Bacillariophyta includes the diatoms which are yellow or brown in color due to the presence of
         brown plastids
              a. may have gliding movement produced by chemical secretions
              b. usually reproduce asexually, sexual stages are rare
              c. some produce resistant cysts
              d. mostly unicellular organisms with overlapping glass like walls of hydrated silica in an organic matrix
              e. have some photosynthetic pigments as in chrysophyta
              f. components of freshwater and marine plankton
              g. store food in for of oil, which also makes cells buoyant

     D. Chrysopyta (Golden Algae)
         1. The phylum Chrysophyta includes the golden algae.
              a. plastids have chlorophyll a, chlorophyll c, yellow and brown carotenoids and xanthophyll
              b. live among freshwater plankton, most are colonial
              c. have flagellated cells with both flagella attached near one end of the cell
              d. store carbohydrates in form of laminarin, a polysaccharide
              e. survive environmental stress by forming resistant cysts
                   (1) Microfossils resembling these cysts have been found in precambrian rocks

     E. Phaeophyta (Brown Algae)
         1. Phaeophyta (brown algae):
              a. largest and most complex of algae
              b. all are multicellular and most are marine inhabitants
              c. have chlorophyll a, chlorophyll c and the carotenoid pigment fucoxanthin
              d. Store carbohydrate food reserves in the form of          laminarin
              e. call walls made of cellulose and algin
         2. Evolutionary adaptations of seaweed
              a. Seaweeds are large, multicellular marine algae which are found in the intertidal and subtitle zones of
              coastal waters




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                   (1) A diverse group of algae including members of the Phaeophyta (brown algae), Rhodophyta (red
                   algae) chlorophyta (green algae)

              b. Habitat of seaweeds poses challenges to survival
                   (1) movement of water due to tides and wind produce a physically active habitat
                   (2) tides alternatively cover and expose the seaweed
              c. Structural adaptations
                   (1) Body of seaweed is call d a Thallus. is plantlike in appearance but has no true roots stems or leaves
                   (2) Thallus consist of rootlike holdfast, stem like stipe (supports blades) leaflike blades (large surfaces
                         for photosynthesis
                   (3) in deeper regions giant brown algae known as kelp can reach 100 meters
              d. Biochemical adaptations that reinforce the anatomical
                   (1) cellulose cell walls also a contain gel forming polysaccharide, serve as cushion during movement
and                      prevents drying out
                   (2) red algae reduce grazing by incorporating calcium carbonate into their cell walls
              e. Seaweeds are used by humans in a variety of ways
                   (1) brown and red algae are used as food
                   (2) marine algae is used as a iodine supplement
                   (3) algin, agar and carageenan used as food and industrial thickeners
                   (4) agar used in microbiological culture media
        3. Alternation of generations in the life cycles of some algae
              a. a variety of life cycles occurs in the algae
              b. Alternation of generations = alternation between             multicellular haploid forms and multicellular
diploid                  forms in a life history
                   (1) also occurs in red and green algae
        4. Life cycle of Lamanaria is example of complex life cycle
              a. diploid individual is a sporophyte because produces spores
              b. haploid is gametophyte because produces gametes
              c. sporophyte and gametophyte take turns producing one another
                   (1) spores develop into gametophytes
                   (2) gametophytes produce gametes which fuse to form zygote that develops into sporophytes
              d. the two generations are heteromorphic because they are morphologically different
              e. In certain algae like Ulva the alteration of generations are isomorphic because they look alike

     F. Rhodophyta (Red Algae)
         1.inhabit warm, tropical marine habitats
         2. contain chlorophyll a, carotenoids, phycobilins and chlorophyll d in some
         3. red color of plastids due to accessory pigment, phycoerythrin
               a. phycoerythrin is a phycobilin, a pigment found only in red algae and cyanobacteria
         4. color of thallus may very with depth as pigmentation changes to optimize photosynthesis
               a. deep water forms are black, moderate is red and shallow is green
               b. one species grows at 250 meters
               c. some tropical species lack pigmentation and survive as parasites on other algae
         5. carbohydrate food reserves stored as floridean starch (similar to glycogen)
         6. cell walls are cellulose with agar and carageenan
         7. most red algae are multicellular and are known as seaweeds
         8. most thalli are filamentous and are often branched forming an interwoven lacy network
         9. All red algae reproduce sexually
               a. have no flagellated stages, unlike other algal protists
               b. alternation of generations is common




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     G. chlorophyta (Green algae)
         1. contain plant like chloroplasts and are related to ancestors of land based plants
              a. 7000 species mostly freshwater few marine
              b. many unicellular, live as plankton, inhabit damp soil, coat snow surfaces
              c. live mutualistically with fungi to make lichens
              d. colonial forms are filamentous (pond scum)
              e. Multicellular forms have large complex structures resembling true plants and comprise a group of
              seaweeds
         2. Evolutionary trends produced current colonial and multicellular varieties, from flagellated unicellular
ancestors
              a. formation of colonies of individual cells (Volvox)
              b. repeated division of nuclei with no cytoplasmic division (Bryopsis)
              c. formation of true multicellular forms as in Ulva
         3. most chlorophytes have complex life histories involving sexual and asexual reproductive stages
              a. conjugation algae produce amoeboid gametes
              b. most gametes are biflagellated
         4. Chlamydomonas is unicellular chlorophyte
              a. During asexual reproduction flagella are resorbed and cell divides twice by mitosis to form 4 cells,
produce            zoospores that grow into adult cells
              b. Sexual reproduction is stimulated by environmental stress
                   (1) many gametes are produced by mitotic division within the wall of parent cell
                   (2) gametes of opposite mating strains pair off and cling together by the tips of their flagella
                   (3) gametes are morphologically indistinguishable , fusion is iogamy
                   (4) fusion of gametes forms a diploid zygote, which secretes a resistant coat that protects it from harsh
                   environments
                   (5) when dormancy of zygote is broken 4 haploids are produced by meiosis
                   (6) emerge and develop into adults

9. Systematists continue to refine their hypothesis of Eukaryotic phylogeny
     A. currently debate is on how many kingdoms we should have
     B. no consensus has been made to change the kingdoms
     C. the proposed differences would be
         1. prokaryotes are split into separate kingdoms , archaebateira and eubacteria
         2. early branching of archaezoans form Eukaryotic tree is recognized by inclusion into the kingdom Archaezoa
         3. Protista is kept but brown algae and related phyla are separated into kingdom chromista
         4. chromista is distinguished by
               a. unusual chloroplasts that have two additional membranes outside of chloroplast envelop
               b. small amount of cytoplasm
               c. present of a vestigial nucleus
               d. chloroplasts by be Eukaryotic endosymbionts
               e. oomycota water molds are also place on this branch , thy lost their chloroplasts
               f. green and red algae will be moved to plant kingdom

10. Multicellularity originated independently many times
     A. Multicellularity evolved several times among the early eukaryotes and gave rise to the multicellular algae, plants
     fungi and animals.
     B. multicellularity allowed for specialization of cells and sharing of the tasks needed for survival.

Scientific ameriacan discussuion on the origins of eukaruyotic diversity.




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     http://www.sciam.com/askexpert/biology/biology7.html

1) Prokaryotes are limited because
   A) They are unable to inhabit many bioms because of their limited metabolic capability
   B) They cannot grow to the size of Eukaryotic cells
   C) They have a small genome hence they can only perform a limited amount of metabolic activities
   D) They cannot form multicelled aggregates needed to inhabit many ecologial niches.

2) A reasonable explination for the evolution of eukaryotes would be
   A) Invagination and specilization of the plasmamembrane
   B) Punctuated equilibrium made rapid changes in the genome producing eukaryotes
   C) A symbiosis between two bacteria to produce a eukaryote
   D) Mutagenesis and doubling of the bacterial genome

3) Water molds are considerd protista because
   A) They are considered fungi
   B) They have genes and biochemistry similar to algae
   C) They are considered algae that have lost their photosynthetic characteristics and have a dapted to an absorptive
      life styel
   D) They have a flaggelated stage of their sexual reproduction
   E) They form resistant cysts.

4) Which of the following are characteristics of Rhodophyta
   A) they produce chlorophyll a
   B) They can live in very deep water
   C) They can live in fresh water
   D) They have an energy storage form similar to glycogen
   E) They can only reproduce asexually

5) Which of the following are parts of an algae
   A) roots
   B) stype
   C) holdfast
   D) thallus
   E) hyphae




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The Protists predate plants and animals by over 1,000,000 years.

Being the oldest Eukaryotes the Protists have the most diversity.
    symbiosis is believed to be the way that Eukaryotes formed
     (endosymbiotic theory)
    most are unicellular, but colonial and simple multicellular forms
     developed here.
    they are nutritionally diverse
      photoautotrophs
      Heterotrophs
      mixotrophs
    Most show a complex life cycle with alternation of generations
     and exchange of gametes.

Previously due to a dearth of techniques and identifying
characteristics Protists were all lumped into one group. We now have
several monophyletic (a taxon derived from a single species, that does not cross
over into any other taxa) candidates that separate members of this group.
    Archaezoa
    Eugleonzoa
    Alveolata
    Unknown phylogeny of the pseudopods.
    Unknown phylogeny of slime
    Stramenophila
    Rhodophyta
    Green algae (in flux)

Hints: Make up a 3x5 note card, write out the domain name on one
side and on the other side give the members of this group. Examples of
species, diseases that they cause or their niche. Typical identifying
characteristics. Be able to match the names with the characteristics
and the characteristics to the names. Be able to describe why each is
so special. Be able to describe its evolutionary significance.



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Archaezoa        diplomonads, trichomonads, microsporidians
    Lack mitochondria and represent early Eukaryotic lineages
    Diplomonads Giardia: flagella, 2 nuclei, no mitochondria, no
     plastids
    Cause diarrhea, transmitted by feces contaminated water
    May have lost the mitochondria (some mitochondrial genes
     found on chromosomes)

Euglenozoa    Euglenoids, kinetoplastids
   include both autotrophic and heterotrophilic flagellates.
   euglenoids (like euglena)
   anterior pocket housing base of flagella
   use paramylum (glucose polymer for storage)
   kinetoplastids have single large mitochondrion and associated
     DNA containing organelle.
   Trypanosoma (African sleeping sickness)
   Euglena autotrophic free living.

Alveolata     Dinoflagellates, apicomplexans, cilliates
    Photosynthetic flagellates and some parasites and some ciliates.
     Have membrane bound cavities under the surface that may
     serve to regulate water or iron.

     dinoflagellates
       Pfiesteria a red tide that produces a toxin to kill fish.
       Internal plates of cellulose
       Nuclear structure is unique
          Some are symbionts of cnidarians that build coral reefs.

     Apicomplexans (sporozoans)
         Plasmodium (malaria)
         The apex of cell contains specialized structures for



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              penetrating host cells
             Are typically parasites that have complex life cycles.
             Know cycle of plasmodium
             Know how the plasmodium parasite will change to avoid
              the immune system.

     cilliates use cilia to move and feed
           most live solitary in fresh water,
           have many thousands of short cilia.
           Has an organized cytoskeleton that forms a specific pattern
             as the cells grow.
           Have 2 types of nuclei (macronucleus, and micronucleus)
           Paramecium undergoes conjugation with the micronucleus
             to ensure sexual shuffling.

The pseudopods are a diverse set of unicellular eukaryotes that move
and feed by means of cellular extensions called pseudopodia. Little is
know about their phylogeny.

Rhizopods (amoebas)
   Amoeba proteus (in laboratory)
   Moves using pseudopodium
   Cytoskeleton of microtubules and microfilaments
   Some secrete a protein shell.
   Meiosis and sex are not known.
   In both fresh and marine environments
   Entomoeba histolytica causes amoebic dysentery

Actinopods (Heliozoans and Radiolarians)
   Moves using very slender pseudopodia (axopodia)
   Have an ornate internal skeleton.
   Most are planktonic




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Foraminiferans (formans)
     Almost all are marine. Attached to rocks or as plankton.
     Have multichambered calcium carbonate shell.
     Extend pseudopodia through the shell.
     Many have symbiotic algae within their shells.
     Use in relative dating, over 90% of species are known as
      fossils.

Closely related to the Ameboid protists are the Slime molds
 Plasmodial slime molds
     o Feeding stage of life cycle is an amoeboid mass called a
        plasmodium. Single mass of individual cells.
     o Nucli are diploid, cell division is synchronous
     o Has cytoplasmic streaming in the mass.
     o Will form sexual structure sporangium in which meiosis takes
        place.
 Cellular slime molds
     o Individual cells function and feed individually
     o When fodd is depleted the cells form an agfregate that
        resembles plasmodial slime mold.
     o Mostly haploid
     o No flaggelated stages, may form fruiting body for asexual
        reproduciton

Stramenopila Diatoms
    diatoms unicellular with glasslike walls of silica
      an unsual chloroplast wieth extra membranes and a vestigial
        nucleus. (and endosymbiont that was an algae)
    golden algae (chrysophytes) biflagelated freshwater
      yellow and brown carotene and xanthophylls accessory
        pigments
      many are mixotropic, can absorb nutrients and ingets larger.
      Dinobryon example of a clonial



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       Can form resistant cysts that remain viable for decades
     Oomycotes water modes
       Some unicellular som have hyphae
       Cells walls made of cellulase
       Are diploid dominant
       Usually have biflagellated cells during reproduciotn
       Most are decomposers and parasites. Cause lots of diseases

     Phaeophytes (brown algae)
       Multicellular
       Most marine
       Chloroplasts and pigments closely related to golden algae and
        diatoms.

Know the structure of seaweed. (note does not really include the brown algae)
  Thallus (sprout)
  Holdfast
  Stipe
  blades

Rhodophyta     red algae
   Phycoetryhrin gives red color.
   Some have lost pigment and are heterotropic parasites.
   Mostly in dark water.
   Have very diverse life cycles.

Plantae       green algae
    Closely related to green plants.


    Multicellularity arose many times. that is why we see such varitey
    in many system.s




                                     Ch 26 p. 15
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                                     Ch 26 p. 16

				
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