Continued from Chapter 26.

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Changing understanding Continued from Chapter 26.

five kingdoms to three domains Three domain

Classification Schemes Right-click slide / select

1 Changing understanding Continued from Chapter 26. Based on phylogenetic research Two kingdoms to five kingdoms to three domains Three domain system: The present tree of life Animation: Classification Schemes Right-click slide / select Play Masters of Adaptation Bacteria and Archaea Chapter 27 1

Structural and functional adaptations contribute to prokaryotic success Unicellular Small Variety of shapes Well organized Cell-Surface Structures Cell wall Bacteria have peptidoglycan Archaea have

Gram-positive bacteria (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye.

Slime layer Fimbriae Pili Taxis Chemotaxis Flagella Cell wall Flagellum Hook Motor Filament 20 nm Cell surface structures Plasma membrane Rod Peptidoglycan layer Evolutionary Origins of Bacterial

2 Structural and functional adaptations contribute to prokaryotic success Unicellular Small Variety of shapes Well organized Cell-Surface Structures Cell wall Bacteria have peptidoglycan Archaea have polysaccharides and proteins but lack peptidoglycan (a) Gram-positive bacteria: peptidoglycan traps crystal violet. Gram-positive bacteria (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye. Gram-negative bacteria Carbohydrate portion of lipopolysaccharide Peptido- Cell glycan wall layer Plasma membrane 10 m Outer membrane Cell Peptidowall glycan layer Plasma membrane Motility Capsule Slime layer Fimbriae Pili Taxis Chemotaxis Flagella Cell wall Flagellum Hook Motor Filament 20 nm Cell surface structures Plasma membrane Rod Peptidoglycan layer Evolutionary Origins of Bacterial Flagella Bacterial flagella are composed of a motor, hook, and filament Many of the flagella s proteins are modified versions of proteins that perform other tasks in bacteria Flagella likely evolved as existing proteins were added to an ancestral secretory system This is an example of exaptation, where existing structures take on new functions through descent with modification Internal Organization and DNA Lack complex compartmentalization Specialized membranes that perform metabolic functions Less DNA than the eukaryotic genome a circular chromosome in the nucleoid region Rings of DNA called plasmids 0.2 m 1 m Respiratory membrane Thylakoid membranes Chromosome Plasmid 1 m 2

Reproduction and Adaptation Prokaryotes reproduce quickly by binary fission and can divide every 1 3 hours Key features of prokaryotic reproduction: They are small They reproduce by binary fission

genetic recombination promote genetic diversity in prokaryotes Prokaryotes have considerable genetic variation Three factors contribute to this genetic diversity: Rapid reproduction Mutation Genetic

3 Reproduction and Adaptation Prokaryotes reproduce quickly by binary fission and can divide every 1 3 hours Key features of prokaryotic reproduction: They are small They reproduce by binary fission They have short generation times Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries Coat Endospore Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes Prokaryotes have considerable genetic variation Three factors contribute to this genetic diversity: Rapid reproduction Mutation Genetic recombination 0.3 m Transformation and Transduction A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria) Recombination Phage A B A B A A B A B A Donor cell Recipient cell Recombinant Conjugation and Plasmids Conjugation is the process where genetic material is transferred between prokaryotic cells F factor is required for the production of pili Sex pilus 1 m R Plasmids and Antibiotic Resistance R plasmids carry genes for antibiotic resistance Antibiotics kill sensitive bacteria, but not bacteria with specific R plasmids Through natural selection, the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics Antibiotic-resistant strains of bacteria are becoming more common Diverse nutritional and metabolic adaptations have evolved in prokaryotes Prokaryotes can be categorized by how they obtain energy and carbon Phototrophs obtain energy from light Chemotrophs obtain energy from chemicals Autotrophs require CO 2 as a carbon source Heterotrophs require an organic nutrient to make organic compounds 3

The Role of Oxygen in Metabolism Prokaryotic metabolism varies with respect to O 2 Obligate aerobes require O 2 for cellular respiration Obligate anaerobes are poisoned by O 2 and use fermentation or

nitrogen in a variety of ways In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N 2 ) to ammonia (NH 3 ) Metabolic Cooperation In the cyanobacterium Anabaena, photosynthetic cells

4 The Role of Oxygen in Metabolism Prokaryotic metabolism varies with respect to O 2 Obligate aerobes require O 2 for cellular respiration Obligate anaerobes are poisoned by O 2 and use fermentation or anaerobic respiration Facultative anaerobes can survive with or without O 2 Nitrogen Metabolism Nitrogen is essential for the production of amino acids and nucleic acids Prokaryotes can metabolize nitrogen in a variety of ways In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N 2 ) to ammonia (NH 3 ) Metabolic Cooperation In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocytes) exchange metabolic products Biofilms Table 27.2 Photosynthetic cells Heterocyst 20 m Archaea Extremophiles Extreme halophiles Halobacterium Extreme thermophiles Sulfobus Methanogens Bacteria Proteobacteria Gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs Some are anaerobic, and others aerobic 4

200 m 2. 300 m 2 m 2 m 1 m 2. 40 m Uptake of K by plants (mg) 2/4/2013 2 m Figure 27.17-a Figure 27.

Nitrosomonas (colorized TEM) Chlamydia (arrows) inside an animal cell (colorized TEM) Leptospira, a spirochete (colorized TEM) Subgroup: Gamma Proteobacteria Subgroup: Delta Proteobacteria Subgroup:

(colorized TEM) Oscillatoria, a filamentous cyanobacterium Streptomyces, the source of many antibiotics (SEM) Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM Gram-positive

5 200 m m 2 m 2 m 1 m m Uptake of K by plants (mg) 2/4/ m Figure a Figure b Subgroup: Alpha Proteobacteria Subgroup: Beta Proteobacteria Chlamydias Spirochetes Alpha Beta Gamma Proteo- Delta bacteria Epsilon Rhizobium (arrows) inside a root cell of a legume (TEM) Nitrosomonas (colorized TEM) Chlamydia (arrows) inside an animal cell (colorized TEM) Leptospira, a spirochete (colorized TEM) Subgroup: Gamma Proteobacteria Subgroup: Delta Proteobacteria Subgroup: Epsilon Proteobacteria Cyanobacteria Gram-Positive Bacteria Thiomargarita namibiensis containing sulfur wastes (LM) Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Helicobacter pylori (colorized TEM) Oscillatoria, a filamentous cyanobacterium Streptomyces, the source of many antibiotics (SEM) Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM Gram-positive bacteria include Actinomycetes, which decompose soil Bacillus anthracis, the cause of anthrax Clostridium botulinum, the cause of botulism Some Staphylococcus and Streptococcus, which can be pathogenic Mycoplasms, the smallest known cells Gram-Positive Bacteria Gram-Positive Bacteria Prokaryotes play crucial roles in the biosphere Chemical Recycling Chemoheterotrophic prokaryotes function as decomposers availability of nitrogen, phosphorus, and potassium for plant growth No Strain 1 Strain 3 bacteria Strain 2 Soil treatment Seedlings growing in the lab Streptomyces, the source of many antibiotics (SEM) Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM) Ecological Interactions Symbiosis larger host and smaller symbiont Mutualism Commensalism Parasitism Prokaryotes have both beneficial and harmful impacts on humans Mutualistic Bacteria Human intestines are home to about 500 1,000 species of bacteria Pathogenic Bacteria Lyme disease is caused by a bacterium and carried by ticks 5

Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present Endotoxins are

6 Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present Endotoxins are released only when bacteria die and their cell walls break down Prokaryotes in Research and Technology Advances in DNA technology Bacteria can now be used to make natural plastics Bioremediation, the use of organisms to remove pollutants from the environment vitamins, antibiotics, and hormones produce ethanol from waste biomass Protists Most eukaryotes are single-celled organisms Protists are eukaryotes Eukaryotic cells have organelles and are more complex than prokaryotic cells Most protists are unicellular, but there are some colonial and multicellular species Structural and Functional Diversity in Protists Protists exhibit more structural and functional diversity than any other group of eukaryotes Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell Protists, the most nutritionally diverse of all eukaryotes, include: Photoautotrophs which contain chloroplasts Heterotrophs absorb organic molecules or ingest larger food particles Mixotrophs 6

plastid-bearing lineage of protists evolved into red and green algae Membranes are represented as dark lines in the cell.

Red alga Secondary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Stramenopiles Plastid Euglenids Green alga Chlorarachniophytes Five Supergroups

7 Figure 28.2 Endosymbiosis in Eukaryotic Evolution Endosymbiosis is the process in which a unicellular organism engulfs another cell Mitochondria aerobic prokaryote Plastids photosynthetic cyanobacterium The plastid-bearing lineage of protists evolved into red and green algae Membranes are represented as dark lines in the cell. Cyanobacterium Primary endosymbiosis Heterotrophic eukaryote One of these membranes was lost in red and green algal descendants. Red alga Secondary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Stramenopiles Plastid Euglenids Green alga Chlorarachniophytes Five Supergroups of Eukaryotes Excavata Chromalveolata Rhizaria Archaeplastida Unikonta Excavates modified mitochondria unique flagella Cytoskeleton Includes the diplomonads, parabasalids, and euglenozoans Diplomonads and Parabasalids Lack plastids, have modified mitochondria, and most live in anaerobic environments Diplomonads Have modified mitochondria called mitosomes Have two equalsized nuclei and multiple flagella Giardia intestinalis, a diplomonad parasite Parabasalids Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females Flagella Undulating membrane 7

8 0.2 m 3 m 2/4/2013 Euglenozoans includes predatory heterotrophs, photosynthetic autotrophs, and parasites The main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella This clade includes the kinetoplastids and euglenids Flagella 0.2 m Kinetoplastids single mitochondrion with an organized mass of DNA called a kinetoplast They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems This group includes Trypanosoma, which causes sleeping sickness in humans 8 m Crystalline rod (cross section) Ring of microtubules (cross section) 9 m Euglenids have one or two flagella that emerge from a pocket at one end of the cell Some species can be both autotrophic and heterotrophic Long flagellum Eyespot Chromalveolates may have originated by secondary endosymbiosis Chromalveolata originated by a secondary endosymbiosis event The proposed endosymbiont is a red alga controversial and includes the alveolates and the stramenopiles Contractile vacuole Nucleus Chloroplast Plasma membrane Euglena (LM) Alveolates Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane The function of the alveoli is unknown The alveolates include Dinoflagellates Apicomplexans Ciliates Flagellum Alveoli Dinoflagellates have two flagella and each cell is reinforced by cellulose plates They are abundant components of both marine and freshwater phytoplankton They are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs Toxic red tides are caused by dinoflagellate blooms Flagella 8

9 40 m Apicomplexans Parasites of animals They spread through their host as infectious cells called sporozoites One end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues Most have sexual and asexual stages that require two or more different host species for completion Plasmodium requires both mosquitoes and humans to complete its life cycle Ciliates use of cilia to move and feed large macronuclei and small micronuclei Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei Conjugation is a sexual process, and is separate from reproduction, which generally occurs by binary fission Paramecium 50 m Stramenopiles important phototrophs as well as several clades of heterotrophs Most have a hairy flagellum paired with a smooth flagellum Stramenopiles include diatoms, golden algae, brown algae, and oomycetes Smooth flagellum Hairy flagellum unicellular algae with a unique two-part, glass-like wall of hydrated silica usually reproduce asexually, and occasionally sexually major component of phytoplankton and are highly diverse Fossilized diatom walls compose much of the sediments known as diatomaceous earth After a diatom population has bloomed, many dead individuals fall to the ocean floor undecomposed This removes carbon dioxide from the atmosphere and pumps it to the ocean floor Diatoms Golden algae are named for their color, which results from their yellow and brown carotenoids The cells of golden algae are typically biflagellated, with both flagella near one end All golden algae are photosynthetic, and some are mixotrophs Most are unicellular, but some are colonial Golden Algae Brown Algae largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called seaweeds Brown algae have the most complex multicellular anatomy of all algae 9

Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike

10 Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades Blade Stipe Holdfast Alternation of Generations A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms Heteromorphic generations are structurally different, while isomorphic generations look similar The diploid sporophyte produces haploid flagellated spores called zoospores The zoospores develop into haploid male and female gametophytes, which produce gametes Fertilization of gamates results in a diploid zygote, which grows into a new sporophyte Oomycetes water molds, white rusts, and downy mildews once considered fungi based on morphological studies Most are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in potato blight caused by Phytophthora infestans Rhizarians are a diverse group of protists defined by DNA similarities DNA evidence supports Rhizaria as a monophyletic clade Amoebas move and feed by pseudopodia; some but not all belong to the clade Rhizaria Rhizarians include radiolarians, forams, and cercozoans Radiolarians Marine protists called radiolarians have tests fused into one delicate piece, usually made of silica Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis The pseudopodia of radiolarians radiate from the central body Foraminiferans or Forams named for porous, generally multichambered shells, called tests Pseudopodia extend through the pores in the test Foram tests in marine sediments form an extensive fossil record Many forams have endosymbiotic algae Pseudopodia 200 m 10

Cercozoans include most amoeboid and flagellated protists with threadlike pseudopodia They are common in marine, freshwater, and soil ecosystems Most are heterotrophs, including parasites and

11 Cercozoans include most amoeboid and flagellated protists with threadlike pseudopodia They are common in marine, freshwater, and soil ecosystems Most are heterotrophs, including parasites and predators Paulinella chromatophora is an autotroph with a unique photosynthetic structure This structure evolved from a different cyanobacterium than the plastids of other photosynthetic eukaryotes Chromatophore Red algae and green algae are the closest relatives of land plants Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont The photosynthetic descendants of this ancient protist evolved into red algae and green algae Land plants are descended from the green algae Archaeplastida is the supergroup that includes red algae, green algae, and land plants Bonnemaisonia hamifera Red Algae 20 cm Green Algae reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll color varies from greenish-red in shallow water to dark red or almost black in deep water Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics Nori 8 mm Dulse (Palmaria palmata) Green algae are named for their grass-green chloroplasts Plants are descended from the green algae Green algae are a paraphyletic group The two main groups are chlorophytes and charophyceans Charophytes are most closely related to land plants Most chlorophytes live in fresh water, although many are marine Other chlorophytes live in damp soil, as symbionts in lichens, or in snow Larger size and greater complexity evolved in chlorophytes by 1. The formation of colonies from individual cells 2. The formation of true multicellular bodies by cell division and differentiation (e.g., Ulva) 3. The repeated division of nuclei with no cytoplasmic division (e.g., Caulerpa) 2 cm (b) Caulerpa, an intertidal chlorophyte (a) Ulva, or sea lettuce Unikonts include protists that are closely related to fungi and animals includes animals, fungi, and some protists This group includes amoebozoans and the opisthokonts (animals, fungi, and related protists) It is unclear whether unikonts separated from other eukaryotes relatively early or late 11

12 Amoebozoans amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia They include slime molds, gymnamoebas, and entamoebas Slime Molds mycetozoans, were once thought to be fungi Molecular systematics places slime molds in the clade Amoebozoa Plasmodial Slime Molds Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange 1 mm 4 cm At one point in the life cycle, plasmodial slime molds form a mass called a plasmodium The plasmodium is not multicellular It is undivided by plasma membranes and contains many diploid nuclei It extends pseudopodia through decomposing material, engulfing food by phagocytosis Cellular Slime Molds form multicellular aggregates in which cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity 200 m 600 m Gymnamoebas Gymnamoebas are common unicellular amoebozoans in soil as well as freshwater and marine environments Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists Entamoebas Entamoebas are parasites of vertebrates and some invertebrates Entamoeba histolytica causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites Opisthokonts include animals, fungi, and several groups of protists 2011 Pearson Education, Inc. 12

10 m 2/4/2013 Protists play key roles in ecological communities Protists are found in diverse aquatic environments Protists often play the role of symbiont or producer Symbiotic Protists Some protist

malaria Pfiesteria shumwayae is a dinoflagellate that causes fish kills Phytophthora ramorum causes sudden oak death Photosynthetic Protists Many protists are important producers that obtain energy

13 10 m 2/4/2013 Protists play key roles in ecological communities Protists are found in diverse aquatic environments Protists often play the role of symbiont or producer Symbiotic Protists Some protist symbionts benefit their hosts Dinoflagellates nourish coral polyps that build reefs Wood-digesting protists digest cellulose in the gut of termites Some protists are parasitic Plasmodium causes malaria Pfiesteria shumwayae is a dinoflagellate that causes fish kills Phytophthora ramorum causes sudden oak death Photosynthetic Protists Many protists are important producers that obtain energy from the sun In aquatic environments, photosynthetic protists and prokaryotes are the main producers In aquatic environments, photosynthetic protists are limited by nutrients These populations can explode when limiting nutrients are added Figure Herbivorous plankton Prokaryotic producers Other consumers Protistan producers Carnivorous plankton Biomass of photosynthetic protists has declined as sea surface temperature has increased If sea surface temperature continues to warm due to global warming, this could have large effects on Marine ecosystems Fishery yields The global carbon cycle 13

Protists 9/11/2017. Endosymbiosis

Protists 9/11/2017. Endosymbiosis Protists Chapter 28 Most eukaryotes are single-celled organisms Protists are eukaryotes Eukaryotic cells have organelles and are more complex than prokaryotic cells Most protists are unicellular, but there