Topic 19 Simple Organisms (Prokaryotes)

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1 Topic 19 Simple Organisms (Prokaryotes) CEB Textbook Chapter 15, pages Mastering Biology, Chapter 15 How did life first arise on Earth? To gain insight, scientists have synthesized from scratch the entire genome of a small bacterium known as Mycoplasma mycoides transplanted the artificial genome into the cells of a closely related species called Mycoplasma capricolum. Biology Society: Has Life Been Created in the Lab? The newly installed genome took over the recipient cells, began cranking out M. mycoides proteins, reproduced to make more cells containing the synthetic M. mycoides genome. Figure 15.1a Earth was formed about 4.6 billion years ago. Prokaryotes evolved by about 3.5 billion years ago, began oxygen production about 2.7 billion years ago, lived alone for more than a billion years, continue in great abundance today. Origin of Earth Ancestor to all present-day life Earth s crust solidifies Precambrian Oldest prokaryotic fossils Atmospheric oxygen begins to appear 4,500 4,000 3,500 3,000 2,500 Millions of years ago 1

2 Figure 15.1b Figure 15.1c Precambrian Precambrian Paleozoic Meso- Cenozoic zoic Bacteria Archaea Protists Plants Fungi Prokaryotes Eukaryotes Oldest eukaryotic fossils Origin of multicellular organisms 2,000 1,500 1,000 Millions of years ago Oldest animal fossils Cambrian explosion Oldest animal fossils Plants colonize l 1, Millions of years ago Animals Extinction of dinosaurs First humans Figure 15.UN03 Major episode Plants fungi colonize l All major animal phyla established First multicellular organisms Oldest eukaryotic fossils Accumulation of O 2 in atmosphere Oldest prokaryotic fossils Origin of Earth Millions of years ago ,200 1,800 2,400 3,500 4,600 Figure 15.2 What if we use a clock analogy to tick down all of the major events in the history of life on Earth? Humans Origin of solar system Earth 2 3 Resolving the Biogenesis Paradox All life today arises by the reproduction of preexisting life, or biogenesis. If this is true, how could the first organisms arise? From the time of the ancient Greeks until well into the 1800s, it was commonly believed that life regularly arises from nonliving matter, an idea called spontaneous generation. Today, most biologists think it is possible that life on early Earth evolved from simple cells produced by chemical physical processes. 2

3 The Process of Science: Can Biological Monomers Form Spontaneously? Observation: Modern biological macromolecules are all composed of elements that were present in abundance on early Earth. Question: Could biological molecules arise spontaneously under conditions like those on early Earth? Hypothesis: A closed system designed to simulate early Earth conditions could produce biologically important organic molecules from inorganic ingredients. Prediction: Organic molecules would form accumulate. Figure 15.4 H 2 O Water vapor Sea CH 4 NH 3 H 2 Condenser Atmosphere Electrode Cold water Cooled water containing organic molecules The Process of Science: Can Biological Monomers Form Spontaneously? Results: After the apparatus had run for a week, an abundance of organic molecules essential for life had collected in the sea, including amino acids, the monomers of proteins. These laboratory experiments have been repeated extended by other scientists support the idea that organic molecules could have arisen abiotically on early Earth. Sample for chemical analysis Miller Urey s experiment Figure 15.UN01 Bacteria Archaea Eukarya Protists Plants Prokaryotes Over millions of years natural selection favored the most efficient pre-cells the first prokaryotic cells evolved. Fungi Animals Prokaryotes lived evolved all alone on Earth for about 2 billion years. 3

4 Colorized TEM PROKARYOTES - They re Everywhere! Prokaryotes are found wherever there is life, have a collective biomass that is at least ten times that of all eukaryotes, thrive in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote, cause about half of all human diseases, are more commonly benign or beneficial. Compared to eukaryotes, prokaryotes are much more abundant typically much smaller. Colorized SEM Figure 4.4 Prokaryotic cells lack a membrane-enclosed nucleus, lack other membraneenclosed organelles, typically have cell walls exterior to their plasma membranes, but display an enormous range of diversity. Plasma membrane Cell wall Capsule Pili Ribosomes Nucleoid Prokaryotic flagellum Prokaryotic Forms The three most common shapes of prokaryotes are 1. spherical (cocci), 2. rod-shaped (bacilli), 3. spiral or curved. SHAPES OF PROKARYOTIC CELLS Spherical (cocci) Rod-shaped (bacilli) Spiral or Curved Prokaryotic Forms All prokaryotes are unicellular. Some species exist as groups of two or more cells, exhibit a simple division of labor among specialized cell types, or are very large, dwarfing most eukaryotic cells. Cyanobacteria (a) Actinomycete Giant Bacterium 4

5 Carbon source Organic compounds Colorized TEM Colorized TEM Prokaryotic Forms Prokaryotic Forms About half of all prokaryotes are mobile, many of these travel using one or more flagella. In many natural environments, prokaryotes attach to surfaces in a highly organized colony called a biofilm, which may consist of one or several species of prokaryotes, may include protists fungi, can show a division of labor defense against invaders, Prokaryotic Forms Prokaryotic Reproduction Biofilm can form on almost any type of surface, including rocks, metal, plastic, organic material including teeth. Most prokaryotes can reproduce by dividing in half by binary fission at very high rates if conditions are favorable. Some prokaryotes form endospores, which are thick-coated, protective cells produced when the prokaryote is exposed to unfavorable conditions. Endospore Colorized TEM Biologists use the phrase mode of nutrition to describe how organisms obtain energy carbon. Energy Phototrophs obtain energy from light. Chemotrophs obtain energy from environmental chemicals. Carbon Autotrophs obtain carbon from carbon dioxide (CO 2 ). Heterotrophs obtain carbon from at least one organic nutrient the sugar glucose, for instance. We can group all organisms according to the four major modes of nutrition if we combine the energy source (phototroph versus chemotroph) carbon source (autotroph versus heterotroph). Figure CO2 MODES OF NUTRITION Energy source Light Photoautotrophs Elodea, an aquatic plant Photoheterotrophs (Prokaryote Only) Chemical Chemoautotrophs (Prokaryote Only) Bacteria from a hot spring Chemoheterotrophs Rhodopseudomonas Kingfisher with prey 5

6 SEM By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: Plaque forming Bacteria Bacteria Archaea Eukarya Protists Plants Prokaryotes 1. Bacteria 2. Archaea (more closely related to eukaryotes). Fungi Animals Archaea Cells Ar Archaea Some archaea are extremophiles. Halophiles thrive in salty environments. Thermophiles inhabit very hot water. Methanogens inhabit the bottoms of lakes swamps aid digestion in cattle deer. 1) Pathogens 2) Chemical Recycling/Decomposers 3) Bioremediation 4) Oxygen Revolution Salt-loving archaea (Halophiles) Heat-loving archaea (Thermophiles) Figure Bacteria other organisms that cause disease are called pathogens. Most pathogenic bacteria produce poisons. Exotoxins are proteins bacterial cells secrete into their environment. Endotoxins are not cell secretions but instead chemical components of the outer membrane of certain bacteria. Bull s-eye rash Tick that carries the Lyme disease bacterium Spirochete that causes Lyme disease 6

7 Biological Weapons In October 2001, endospores of the bacterium that causes anthrax were mailed to members of the news media the U.S. Senate. Five people died from this attack. Another bacterium considered to have dangerous potential as a weapon is Clostridium botulinum, producer of the exotoxin botulinum, which blocks transmission of nerve signals that cause muscle contraction is the deadliest poison on Earth. Biological Weapons The bacterium enterobacteria Yersinia pestis that causes plague is also a potential biological weapon, is carried by rodents, transmitted by fleas, Infects lymph nodes produces egg-size swellings called buboes under the skin, can be treated with antibiotics if diagnosed early. Prokaryotes play essential roles in chemical cycles in the environment the breakdown of organic wastes dead organisms. 7

8 Bioremediation is the use of organisms to remove pollutants from water, air, soil. A familiar example is the use of prokaryotic decomposers in sewage treatment. Certain bacteria can decompose petroleum are useful in cleaning up oil spills. Figure Rotating arm spraying liquid wastes Rock bed coated with aerobic prokaryotes fungi Photosynthetic bacteria were most likely responsible for rise in levels of oxygen in the atmosphere 2500 mya which allowed the first respiring eukaryotes to develop Liquid wastes Outflow Two main domains Bacteria Archaea Three common shapes Spherical, Rod, Spiral Four main modes of nutrition Photoautotroph, Photoheterotroph (unique to prokaryotes), Chemoautotroph (unique to prokaryotes), Chemoheterotroph Bacterial impact on life on Earth Pathogens, Chemical Recycling, Bioremediation, Oxygen Revolution Topic 20 Microbes with Complex Cells (Eukaryotes) CEB Textbook Chapter 15 pages , & Chapter 16, pages Mastering Biology, Chapters

9 Colorized SEM LM Learning outcomes: After studying this topic you should be able to: Figure 15.UN02 Bacteria Prokaryotes Explain the fundamental difference between protists fungi as compared to bacteria archaea. List the four main types of protists briefly describe an example of each type. Describe the basic structure of fungi explain how they feed reproduce. Describe examples of important impacts that fungi have in medicine agriculture. Archaea Eukarya Protists Plants Fungi Animals Protists are eukaryotes that are not fungi, animals, or plants, mostly unicellular, ancestral to all other eukaryotes. Eukaryotic cells evolved by the infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system a process known as endosymbiosis. Endosymbiosis refers to one species living inside another host species is the process by which eukaryotes gained mitochondria chloroplasts. Figure Figure Plasma membrane DNA Cytoplasm Ancestral prokaryote Membrane infolding Endoplasmic reticulum Nucleus Photosynthetic prokaryote Endosymbiosis Aerobic heterotrophic prokaryote Chloroplast Nuclear envelope Mitochondrion Cell with nucleus endomembrane system (a) Origin of the endomembrane system (b) Origin of mitochondria chloroplasts Photosynthetic eukaryotic cell (a) An autotroph: Caulerpa, a multicellular alga (b) A heterotroph: parasitic trypanosome (c) A mixotroph: Euglena 9

10 LM TEM LM Colorized SEM Colorized SEM Colorized TEM The Diversity of Protists Protist habitats are diverse include oceans, lakes, ponds, damp soil leaf litter, the bodies of host organisms with which they share mutually beneficial relationships, such as unicellular algae reefbuilding coral animals, cellulose-digesting protists termites. 1)Protozoans 2)Slime Molds 3)Algae 4)Seaweed Figure Main Types of Protozoan Protozoans are protists that live primarily by ingesting food are called A flagellate: Giardia Another flagellate: Trichomonas An amoeba Apical complex Cilia A foram Red blood cell An apicomplexan A ciliate Cell mouth Main types of Protozoans a) Flagellates - Protozoans with flagella are typically free-living, but some are nasty parasites. b) Amoebas are characterized by great flexibility in their body shape the absence of permanent organelles for locomotion. Most species move feed by means of pseudopodia (singular, pseudopodium), temporary extensions of the cell. Main types of Protozoans c) Forams Are protozoans which have shells. d) Apicomplexans are named for a structure at their apex (tip) that is specialized for penetrating host cells tissues, all parasitic, able to cause serious human diseases, such as malaria caused by Plasmodium. 10

11 TEM LM Figure 15.22e Main types of Protozoans Red blood cell Apical complex An apicomplexan Another apicomplexan is Toxoplasma, occurring in the digestive tracts of millions of people in the United States but held in check by the immune system. A woman newly infected with Toxoplasma during pregnancy can pass the parasite to her unborn child, who may suffer nervous system damage. Main types of Protozoans e) Ciliates are protozoans that are named for their use of hair-like structures called cilia to move sweep food into their mouths, are mostly free-living (nonparasitic), such as the freshwater ciliate Paramecium, include heterotrophs mixotrophs. Figure 15.22f Cilia A ciliate Cell mouth Slime molds resemble fungi in appearance lifestyle due to convergence, but are more closely related to amoebas. The two main groups of these protists are plasmodial slime molds cellular slime molds. 11

12 LM Types of Slime Molds Plasmodial slime molds are named for the feeding stage in their life cycle, an amoeboid mass called a plasmodium, are decomposers on forest floors, can be large. Types of Slime Molds Cellular slime molds have an interesting complex life cycle of successive stages: a feeding stage of solitary amoeboid cells, a swarming stage as a sluglike colony that can move function as a single unit, a stage during which they generate a stalk-like multicellular reproductive structure. Figure Life stages of a cellular slime mold 2 Slug-like colony 1 Amoeboid cells 3 Reproductive structure 3. Unicellular Colonial Algae (Protists) Algae are photosynthetic protists whose chloroplasts support food chains in freshwater marine ecosystems. Many unicellular algae are components of plankton, the communities of mostly microscopic organisms that drift or swim weakly in aquatic environments. Unicellular algae include dinoflagellates, with two beating flagella external plates made of cellulose, diatoms, with glassy cell walls containing silica, green algae. 12

13 SEM Colorized SEM LM LM 3. Unicellular Colonial Algae (Protists) Figure Green algae are unicellular in most freshwater lakes ponds, sometimes flagellated, such as Chlamydomonas, (a) A dinoflagellate, with its wall of protective plates (b) A sample of diverse diatoms, which have glassy walls sometimes colonial, forming a hollow ball of flagellated cells as seen in Volvox. (c) Chlamydomonas, a unicellular green alga with a pair of flagella (d) Volvox, a colonial green alga Seaweeds Seaweeds are large, multicellular marine algae, grow on or near rocky shores, are only similar to plants because of convergent evolution, are most closely related to unicellular algae, are often edible. Seaweeds are classified into three different groups, based partly on the types of pigments present in their chloroplasts: 1. green algae, 2. red algae, 3. brown algae (including kelp). Multicellular organisms have specialized cells that are dependent on each other perform different functions, such as feeding, waste disposal, gas exchange, protection. Green algae Red algae Brown algae Colonial protists likely formed the evolutionary links between unicellular h?v=he9fsegri3a multicellular organisms. The colonial green alga Volvox demonstrates one level of specialization cooperation. 13

14 Figure Figure Unicellular protist An ancestral colony may have formed when a cell divided remained attached to its offspring. Unicellular protist An ancestral colony may have formed when a cell divided remained attached to its offspring. Cells in the colony may have become specialized interdependent. Foodsynthesizing cells Locomotor cells Figure Unicellular protist An ancestral colony may have formed when a cell divided remained attached to its offspring. Locomotor cells Cells in the colony may have become specialized interdependent. Foodsynthesizing cells Additional specialization may have led to sex cells (gametes) nonreproductive cells (somatic cells). Gamete Somatic cells Any Eukaryote that is not a fungi, animal or plant! Four main types 1) Protozoans (flagellates, amoebas, apicomplexans, ciliates) aquatic ingest their food 2) Slime moulds decomposers, resemble fungi but not closely related 3) Algae (dinoflagellates, diatoms, unicellular green algae) photosynthetic, support food chains in fresh water marine ecosystems 4) Seaweed (green, red brown algae) large multicellular marine algae FUNGI Fungi are eukaryotes, typically multicellular, more closely related to animals than plants, arising from a common ancestor about 1.5 billion years ago. come in many shapes sizes represent more than 100,000 species. Fungi have unique structures forms of nutrition. 14

15 Colorized SEM Colorized SEM Colorized SEM Figure Bud Orange fungi A fairy ring Mold Budding yeast Roundworm Predatory fungus Body of fungus The bodies of most fungi are constructed of threadlike filaments called hyphae. Hyphae are minute threads of cytoplasm surrounded by a plasma membrane cell walls mainly composed of chitin (not cellulose like in plants!). Hyphae branch repeatedly, forming an interwoven network called a mycelium (plural, mycelia), the feeding structure of the fungus. Figure Fungi are chemoheterotrophs acquire their nutrients by absorption. A fungus is a decomposer digests food outside its body by secreting powerful digestive enzymes to break down the food absorbs the simpler food compounds. Reproductive structure Hyphae Mycelium Spore-producing structures Fungal Reproduction Mushrooms arise from an underground mycelium mainly function in reproduction. Fungi reproduce by releasing haploid spores that are produced either sexually or asexually. Animation: Fungal Reproduction Nutrition Right click slide / select Play 15

16 Fungi as Decomposers Fungi have an enormous ecological impact many interactions with humans. Fungi bacteria are the principal decomposers of ecosystems keep ecosystems stocked with the inorganic nutrients necessary for plant growth. Without decomposers, carbon, nitrogen, other elements would accumulate in nonliving organic matter. Molds can destroy fruit, grains, wood, human-made material. Figure 16.24b Parasitic fungi absorb nutrients from the cells or body fluids of living hosts. Can cause serious economic losses in agriculture Of the 100,000 known species of fungi, about 30% make their living as parasites, including Dutch elm disease deadly ergot, which infests grain. (a) An American elm tree killed by Dutch elm Potato blight disease fungus (b) Ergots Parasitic Fungi About 50 species of fungi are known to be parasitic in humans other animals, causing lung vaginal yeast infections such as thrush athlete s foot facial eczema Observation: In 1692, eight young girls were accused of being witches had symptoms consistent with ergot poisoning. Question: Did an ergot outbreak cause the witch hunt? Hypothesis: The girls symptoms were the result of ergot poisoning. Prediction: The historical facts would be consistent with this hypothesis. 16

17 Colorized SEM The Process of Science: Did a Fungus Lead to the Salem Witch Hunt? Results: Agricultural records from 1691, before the symptoms appeared, indicated a particularly warm wet year, in which ergot thrives. Records from the following year, when accusations of witchcraft died down, indicate a dry year consistent with an ergot die-off. This correlation is consistent with the hypothesis but not conclusive. Fungi are commercially important. Humans eat them use them to produce medicines such as penicillin (the first ever antibiotic!), decompose wastes, produce bread (yeast), beer, wine, cheeses. Mushrooms Truffles are grown for food Figure Figure Penicillium Zone of inhibited growth Staphylococcus Chicken of the woods Chanterelle mushrooms Giant puffball Figure Mutually beneficial symbiotic relationships between plants fungi Examples include Mycorrhizae, a fungi which increases the surface area of plant roots allowing them to absorb more minerals water from the soil, Lichens, the association of fungi algae. Algae can create sugars by photosynthesis which feeds both. Fungi increases surface area allowing more water absorption. Lichens: symbiotic associations of fungi algae Algal cell Fungal hyphae 17

18 Unicellular or multicellular eukaryotes Chemoheterotrophs Digest their food externally absorb nutrients, more closely related to animals than plants Consist of threadlike hyphae, forming a mycelium Reproduce by releasing spores Ecological Impact of Fungi Principal decomposers of ecosystems Parasites of people other animals plants. Beneficial to some plants to increase root surface area. Important in manufacture of food (bread, beer, wine, mushrooms, truffles) antibiotics Symbiotic Relationship with plants Fungi live on roots of plants (gets nutrients) increase surface area of plant roots (plant can absorb more water/minerals Homework Prokaryotes Eukaryotes 1) Unit Assessment Topic ) Mastering Biology Assignment Prokaryotes Eukaryotes 3) Mastering Biology activities: Prokaryotic Cell Structure Function, Classification of Prokaryotes 4) Complete the tables in study notes for Topic ) Fill in Key Terms tables for Topic VIDEOS Crash course in Fungi Fungi Lesson Crash course Archaea, Bacteria (Prokaryotes) Protists (Unicellular Eukaryotes) Bacteria Lesson 18