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Characterizing and Classifying Eukaryotes
Chapter 12 Characterizing and Classifying Eukaryotes
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General Characteristics of Eukaryotic Organisms
Five major groups Protozoa Fungi Algae Water molds Slime molds Include both human pathogens and organisms vital for human life © 2012 Pearson Education Inc.
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General Characteristics of Eukaryotic Organisms
Reproduction in Eukaryotes More complicated than reproduction in prokaryotes Eukaryotic DNA packaged as chromosomes in the nucleus Have variety of methods of asexual reproduction Many reproduce sexually by forming gametes and zygotes Algae, fungi, and some protozoa reproduce both sexually and asexually © 2012 Pearson Education Inc.
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General Characteristics of Eukaryotic Organisms
Reproduction in Eukaryotes Nuclear division Nucleus has one or two complete copies of genome Single copy (haploid) Most fungi, many algae, some protozoa Two copies (diploid) Remaining fungi, algae, and protozoa Two types Mitosis Meiosis © 2012 Pearson Education Inc.
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General Characteristics of Eukaryotic Organisms
Reproduction in Eukaryotes Nuclear division Mitosis Cell partitions replicated DNA equally between two nuclei Maintains ploidy of parent nucleus Four phases Prophase Metaphase Anaphase Telophase © 2012 Pearson Education Inc.
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Figure 12.1a Mitosis Mitosis Diploid nucleus (2n) DNA replication
Prophase I Chromosome (two chromatids) Centromere Metaphase Spindle Anaphase Telophase Nuclear envelope Two diploid nuclei (2n)
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General Characteristics of Eukaryotic Organisms
Reproduction in Eukaryotes Nuclear division Meiosis Nuclear division that partitions chromatids into four nuclei Diploid nuclei produce haploid daughter nuclei Two stages – meiosis I and meiosis II Each stage has four phases Prophase Metaphase Anaphase Telophase © 2012 Pearson Education Inc.
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Figure 12.1b1 Meiosis I Meiosis Diploid nucleus (2n) DNA replication
Prophase I Tetrad (two homologous chromosomes, four chromatids) Late prophase I Crossing over MEIOSIS I Metaphase I Anaphase I Chromosome (two chromatids) Telophase I
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Four haploid nuclei (1n)
Figure 12.1b2 Meiosis II Prophase II Metaphase II Anaphase II MEIOSIS II Telophase II Nuclear envelope Four haploid nuclei (1n)
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General Characteristics of Eukaryotic Organisms
Reproduction in Eukaryotes Cytokinesis (cytoplasmic division) Typically occurs simultaneously with telophase of mitosis In some algae and fungi, postponed or does not occur at all Results in multinucleated cells called coenocytes © 2012 Pearson Education Inc.
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Figure 12.2 Different types of cytoplasmic division-overview
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Merozoites Nucleus Schizont Multiple mitoses Cytokinesis
Figure Schizogony Merozoites Nucleus Schizont Multiple mitoses Cytokinesis
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Figure 12.4 The changing classification of eukaryotes over the centuries-overview
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Diverse group defined by three characteristics
Protozoa Diverse group defined by three characteristics Eukaryotic Unicellular Lack a cell wall Motile by means of cilia, flagella, and/or pseudopodia Except subgroup, apicomplexans © 2012 Pearson Education Inc.
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Distribution of Protozoa
Require moist environments Most live in ponds, streams, lakes, and oceans Critical members of plankton Others live in moist soil, beach sand, and decaying organic matter Very few are pathogens © 2012 Pearson Education Inc.
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Morphology of Protozoa
Great morphologic diversity Some have two nuclei Macronucleus Contains many copies of the genome Micronucleus Variety in number and kinds of mitochondria Some have contractile vacuoles All produce trophozoites; some produce cysts © 2012 Pearson Education Inc.
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Figure 12.5 Contractile vacuole-overview
Closed vacuole Open vacuole
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Protozoa Nutrition of Protozoa Most are chemoheterotrophic
Obtain nutrients by phagocytizing bacteria, decaying organic matter, other protozoa, or the tissues of host Few absorb nutrients from surrounding water Dinoflagellates and euglenoids are photoautrophic © 2012 Pearson Education Inc.
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Reproduction in Protozoa
Most reproduce asexually only Binary fission or schizogony Few also have sexual reproduction Some become gametocytes that fuse with one another to form diploid zygotes Some utilize a process called conjugation © 2012 Pearson Education Inc.
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Figure 12.6 Sexual reproduction via conjugation in ciliates
Diploid micronuclei Haploid micronuclei Meiosis of micronuclei produces four haploid micronuclei in each. Three micronuclei in each disintegrate; the remaining two replicate by mitosis. Compatible mates Mates couple. Mates each swap one micronucleus. Haploid micronucleus (1n) Micronucleus (50n) Diploid micronucleus (2n) Partners separate. Three cytokineses partition a macronucleus and a micronucleus into each of four daughter cells. Original macronucleus disintegrates. Four micronuclei become macronuclei by replicating chromosomes numerous times; four micronuclei remain micronuclei. Three mitoses without cytokinesis produce eight micronuclei. The two different micronuclei fuse to form diploid micronucleus.
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Classification of Protozoa
Based on 18S rRNA and features visible by electron microscopy One scheme classifies into six taxa © 2012 Pearson Education Inc.
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Figure 12.7 Trichonympha acuta, a parabasalid with prodigious flagella
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Classification of Protozoa
Diplomonadida Lack mitochondria, Golgi bodies, peroxisomes Prominent example is Giardia © 2012 Pearson Education Inc.
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Short second flagellum
Figure 12.8a Euglena Flagellum “Eyespot” Short second flagellum Contractile vacuole Paramylon granule Nucleus Chloroplasts Pellicle
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Figure 12.8b Trypanosoma Kinetoplast Nucleus
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Figure 12.9 Alveoli membrane-bound structures found in some protozoa
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Figure 12.10 A predatory ciliate, Didinium, devouring another ciliate, Paramecium
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Figure 12.11 Peridinium, a motile armored dinoflagellate
Cellulose plate Transverse flagellum Longitudinal flagellum
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Figure Rhizaria called foraminifera have multichambered, snail-like shells of calcium carbonate
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Figure 12.13 Rhizaria called radiolarians have ornate shells of silica
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Figure 12.14a A plasmodial (acellular) slime mold
Haploid Compatible myxamoebae fuse. Myxamoebae germinate from spores. Spore (n) Zygote (2n) Haploid spores are released. Plasmodium Sporangium Coenocytic plasmodium (2n) Sporania grow from plasmodial masses. Diploid
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Figure 12.14b A cellular slime mold
Spores are released. Haploid Nucleus Spore Myxamoeba germinates from spore. Sporangium Fruiting body with sporangium Slug Slug forms stalk. Myxamoebae congregate to form pseudoplasmodium (slug), but they retain their individuality.
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Have cell walls typically composed of chitin
Fungi Chemoheterotrophic Have cell walls typically composed of chitin Do not perform photosynthesis Lack chlorophyll Related to animals © 2012 Pearson Education Inc.
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The Significance of Fungi
Decompose dead organisms and recycle their nutrients Help plants absorb water and minerals Used for food and in manufacture of foods and beverages Produce antibiotics Serve as important research tools 30% cause diseases of plants, animals, and humans Can spoil fruit, pickles, jams, and jellies © 2012 Pearson Education Inc.
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Figure 12.15 Fungal morphology-overview
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Figure 12.16 A fungal mycelium growing on a leaf
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Fungi Nutrition of Fungi Acquire nutrients by absorption
Most are saprobes Some trap and kill microscopic soil-dwelling nematodes Haustoria allow some to derive nutrients from living plants and animals May use ionizing radiation as energy source Most fungi are aerobic Many yeasts are facultative anaerobes © 2012 Pearson Education Inc.
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Figure 12.17 Predation of a nematode by the fungus Arthrobotrys
Hyphal loop
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Fungi Reproduction in Fungi
All have some means of asexual reproduction involving mitosis and cytokinesis Most also reproduce sexually © 2012 Pearson Education Inc.
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Fungi Reproduction in Fungi Budding and asexual spore formation
Yeasts bud in manner similar to prokaryotic budding Pseudohypha Series of buds that remain attached to one another and to parent cell Filamentous fungi produce lightweight spores that disperse over large distances © 2012 Pearson Education Inc.
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Figure 12.18 Representative asexual spores of molds-overview
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Figure 12.19 The process of sexual reproduction in fungi
Tips fuse Dikaryotic stage (nn) Dikaryon 2 nuclei per cell Diploid stage (2n) Meiosis Nuclei fuse Haploid stage (n)
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Classification of Fungi
Division Zygomycota Division Ascomycota Division Basidiomycota Deuteromycetes © 2012 Pearson Education Inc.
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Figure 12.20 Life cycle of the zygomycete Rhizopus
Asexual Reproduction Sexual Reproduction Zygosporangium matures. Nuclear meioses occurs (not shown). Spore germinates to produce aseptate mycelium (1n). Zygosporangium produces an asexual sporangium (1n). Vegetative mycelium grows. Sporangium bursts to release spores. Zygosporangium forms. (2n) Mating hyphae join and fuse. Dikaryon (nn) Spores (1n) are released from sporangium. Haploid nuclei (1n) Sporangiospores Sporangium (1n) Gamete forms at tip of hypha. Sporangio- phore Aerial hypha produces a sporangium. Spore germinates.
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Figure 12.21 Ascocarps (fruiting bodies) of the common morel, Morchella esculenta
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Figure 12.22 Life cycle of an ascomycete
Asexual Reproduction Sexual Reproduction (called Eupenicillium at this stage) Hyphal tip undergoes cytoplasmic fusion with opposite mating type. Vegetative mycelium grows. Conidiospore germinates to produce mycelium. Dikaryon (nn) forms. Conidiospores are released from conidiophore. Nuclei fuse in terminal cells to form 2n nuclei. Dikaryon Ascospores germinate to produce mycelia. Ascus Conidiospore Ascospores Meiosis produces four haploid (1n) cells. Ascus opens to release ascospores. Conidiophore Hypha produces conidiophores and conidiospores. Ascus Ascospore Mitosis produces eight haploid ascospores on each tip.
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Figure 12.23 Basidiocarps (fruiting bodies) of the bird's nest fungus, Crucibulum
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Figure 12.24 Sexual life cycle of Amanita muscaria, a poisonous basidiomycete
Cross section of gill showing hyphae.. Pair of haploid nuclei fuse. 2n Meiosis produces four haploid nuclei. Four basidiospores (1n) develop. Gills Basidium Basidiospore is released. Basidiospores germinate to produce mycelia. Dikaryotic mycelium growing in soil produces basidiocarp (mushroom). Dikaryon (nn) Hyphae of opposite mating types fuse belowground to produce dikaryotic mycelium.
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Classification of Fungi
Deuteromycetes Heterogeneous collection of fungi with unknown sexual stages rRNA analysis revealed that most deuteromycetes belong in the division Ascomycota © 2012 Pearson Education Inc.
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Fungi Lichens Partnerships between fungi and photosynthetic microbes
Abundant throughout the world, particularly in pristine habitats Grow in almost every habitat On soil, rocks, leaves, tree bark, other lichens, even tortoises Occur in three basic shapes Fruticose, crustose, foliose Create soil from weathered rocks Eaten by many animals © 2012 Pearson Education Inc.
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Figure 12.25 Makeup of a lichen
Ascocarp of fungus Soredium Algal cell Fungal hyphae Fungal hyphae Phototrophic layer Substrate
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Figure 12.26 Gross morphology of lichens
Foliose Crustose Fruticose
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Have sexual reproductive structures
Algae Simple, eukaryotic phototrophs that carry out oxygenic photosynthesis using chlorophyll a Have sexual reproductive structures Every cell becomes a gamete Differ widely in distribution, morphology, reproduction, and biochemical traits © 2012 Pearson Education Inc.
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Algae Distribution of Algae Most are aquatic
Live in the photic zone of fresh, brackish, and saltwater Accessory photosynthetic pigments that trap energy of light and pass it to chlorophyll a © 2012 Pearson Education Inc.
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Algae Morphology of Algae
Unicellular, colonial, or have simple multicellular bodies (thalli) © 2012 Pearson Education Inc.
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Algae Reproduction in Algae Unicellular algae Multicellular algae
Asexual reproduction involves mitosis followed by cytokinesis Sexual reproduction forms zygotes from individual gametes Zygote undergoes meiosis Multicellular algae Reproduce asexually by fragmentation Reproduce sexually with alternation of generations © 2012 Pearson Education Inc.
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Diploid (2n) generation
Figure Alternation of generations in algae, as occurs in the green alga Ulva Diploid (2n) generation Meiosis Zygote Diploid individual Male and female haploid spores Fusion Male gamete Male haploid individual Female gamete Female haploid individual Haploid (1n) generation
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Classification of Algae
Classification not settled Classified into groups named for their photosynthetic pigments © 2012 Pearson Education Inc.
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Classification of Algae
Division Chlorophyta Green algae Often considered progenitors of plants © 2012 Pearson Education Inc.
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Figure 12.28 Antithamnion, a red alga
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“Hairy” flagellum Whiplike flagellum
Figure The two types of flagella of the sperm of the brown alga Fucus “Hairy” flagellum Whiplike flagellum
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Figure 12.30 Portion of the giant kelp Macrocystis, a brown alga
Pneumocyst
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Figure 12.31 Coscinodiscus, a diatom
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Differ from fungi in the following ways:
Water Molds Differ from fungi in the following ways: Have tubular cristae in their mitochondria Cell walls are of cellulose instead of chitin Spores have two flagella One whiplike and one tinsel-like Have true diploid thalli © 2012 Pearson Education Inc.
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Figure 12.32 The important role of water molds in recycling organic nutrients in aquatic habitats
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Parasitic worms have microscopic infective and diagnostic stages
Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors Parasitic worms have microscopic infective and diagnostic stages Arthropod vectors are animals that carry pathogens Mechanical vectors Biological vectors Disease vectors belong to two classes of arthropod Arachnida Insecta © 2012 Pearson Education Inc.
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Arachnids Adult arachnids have four pairs of legs
Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors Arachnids Adult arachnids have four pairs of legs Ticks are the most important arachnid vectors Hard ticks are most prominent tick vectors A few mite species transmit rickettsial diseases © 2012 Pearson Education Inc.
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Insects Adult insects have three pairs of legs and three body regions
Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors Insects Adult insects have three pairs of legs and three body regions Include Fleas Lice Flies Mosquitoes Kissing bugs © 2012 Pearson Education Inc.
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Figure 12.33 Representative arthropod vectors-overview
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