Chapter 16: Evolution Of Microbial Life PDF

Because learning changes everything. ® Chapter 16 Evolution of Microbial Life Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw H...

Because learning changes everything. ® Chapter 16 Evolution of Microbial Life Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  16.1 How Cells Arose 2 The earth formed 4.5 billion years ago. The first life originated around 2.5 billion years ago. Figure 16.1 A clock of biological time Access the text alternative for slide images. © McGraw Hill, LLC 2  16.1 How Cells Arose 3 When life formed, the earth’s atmosphere contained little or no oxygen but contained lots of hydrogen-rich gases, such as hydrogen sulfide (H2S), ammonia (NH3), and methane (CH4). © McGraw Hill, LLC 3  16.1 How Cells Arose 4 Stanley Miller and Harold Urey reconstructed the oxygen-free atmosphere of the early earth in their laboratory. They subjected it to the lighting and UV radiation that it would have experienced then. They found that many of the building blocks of organisms formed spontaneously. They concluded that life may have evolved in a “primordial soup” of biological molecules formed in the early earth’s oceans. © McGraw Hill, LLC 4  16.1 How Cells Arose 5 Critics of the Miller-Urey experiment say that because there was no oxygen in the early atmosphere, there would have been no layer of ozone to provide protection from UV. The UV radiation would have destroyed ammonia and methane in the atmosphere, without which, the building blocks cannot be synthesized. © McGraw Hill, LLC 5  16.1 How Cells Arose 6 The bubble model proposes that life’s building blocks could have formed within bubbles on the ocean’s surface. The bubbles would also provide protection from UV radiation. © McGraw Hill, LLC 6  Figure 16.2: A chemical process involving bubbles may have preceded the origin of life Access the text alternative for slide images. © McGraw Hill, LLC 7  16.1 How Cells Arose 7 When organic molecules are present in water, they tend to cluster together in structures called microspheres. These microspheres have many cell-like properties. The first cells could have formed similar to the way microspheres form. The first macromolecules to form might have been RNA because they are more stable than DNA. © McGraw Hill, LLC 8  16.2 The Simplest Organisms 1 Prokaryotes are the simplest and most abundant organisms on earth. Two types of prokaryotes: bacteria and archaea. Prokaryotes play important roles in the biosphere. Cycling minerals. Creating oxygen in earth’s atmosphere. Causing many disease. © McGraw Hill, LLC 9  16.2 The Simplest Organisms 2 Prokaryotes are single-celled organisms too small to see with the naked eye. Each cell has a single circular piece of DNA not confined by a nuclear membrane. © McGraw Hill, LLC 10  16.2 The Simplest Organisms 3 Prokaryotes differ from eukaryotes in Internal compartmentalization. Cell size. Unicellularity. Chromosomes. Cell division. Flagella. Metabolic diversity. © McGraw Hill, LLC 11  Table 16.1: Prokaryotes Compared to Eukaryotes Internal compart-mentalization. Unlike eukaryotic cells, prokaryotic cells contain no internal compartments, no internal membrane system, and no cell An illustration shows the sectional view of a prokaryotic cell with cilia and flagella. nucleus. Cell size. Most prokaryotic cells are only about 1 micrometer in diameter, whereas most eukaryotic cells are well over 10 times that size. An illustration shows the sectional view of a prokaryotic cell and eukaryotic cell. Unicellularity. All prokaryotes are fundamentally single-celled. A micrograph shows the unicellular bacteria. Kwangshin Kim/Science Source Chromosomes. Prokaryotes do not possess chromosomes as eukaryotes do. Instead, their DNA exists as a single circle in the cytoplasm. An illustration shows a prokaryotic chromosome without free ends and eukaryotic chromosomes in an X-shape. Cell division. Cell division in prokaryotes takes place by binary fission. In eukaryotes, microtubules pull chromosomes to opposite poles during mitosis. An illustration shows binary fission in prokaryotes where the cell divides into two and mitosis in eukaryotes where the mitotic spindles occur. Flagella. Prokaryotic flagella are composed of a single fiber of protein that spins like a propeller. Eukaryotic flagella are more complex structures, with a 9 An illustration shows a simple bacterial flagellum. + 2 arrangement of microtubules. Metabolic diversity. Prokaryotes possess many metabolic abilities that eukaryotes do not, including anaerobic photosynthesis and the ability to fix A micrograph of chemoautotrophs in a spherical shape. atmospheric nitrogen. Eye of Science/Science Source © McGraw Hill, LLC 12  16.2 The Simplest Organisms 4 Bacterial cells are simple in form. Rod-shaped (bacilli). Spherical (cocci). Spirally coiled (spirilla). A few kinds of bacteria aggregate into stalked structures or filaments. The prokaryotic cell’s plasma membrane is encased within a cell wall. The cell wall of bacteria is different than that of archaea and those found in eukaryotes. In bacteria, the cell wall is made of peptidoglycan. © McGraw Hill, LLC 13  16.2 The Simplest Organisms 5 In many bacteria, called Gram-negative bacteria, a thinner cell wall is surrounded by an outer membrane. The outer membrane prevents the cell wall from taking up a type of stain called a Gram stain. Gram-negative bacteria are more resistant to antibiotics. In Gram-positive bacteria, there is no outer membrane and the cell wall is much thicker. Without the outer membrane, these bacteria take up the Gram stain. © McGraw Hill, LLC 14  16.2 The Simplest Organisms 6 Additional features of some bacteria include: Flagella: long strands of protein used in swimming. Pili: shorter strands that act as docking cables. Endospores: thick-walled enclosures of DNA and a small bit of cytoplasm that are extremely resistant to environmental stress. © McGraw Hill, LLC 15  16.2 The Simplest Organisms 7 All prokaryotes can reproduce via binary fission. After replicating DNA, the plasma membrane and cell wall grow inward and eventually divide the cell. Some bacteria can exchange genetic information via plasmids passed from one cell to another. This process is called conjugation and occurs through a special connection that forms between bacterial cells called a conjugation bridge. © McGraw Hill, LLC 16  Figure 16.3: Bacterial conjugation Access the text alternative for slide images. © McGraw Hill, LLC 17  16.3 Structure of Viruses 1 Viruses are parasitic chemicals, segments of DNA (or sometimes RNA) wrapped in a protein coat called a capsid. They are not alive because they possess only a portion of the properties of organisms and cannot reproduce on their own. They are very small in size. They infect all organisms. The capsid may be encased by a membrane-like envelope rich in proteins and lipids. There are structural differences among types of viruses. © McGraw Hill, LLC 18  Figure 16.4: The structure of plant, bacterial, and animal viruses Access the text alternative for slide images. © McGraw Hill, LLC 19  16.3 Structure of Viruses 2 Emerging viruses arise in one species and pass to another, causing a new disease. Influenza virus has been one of the most lethal viruses in human history. AIDS (HIV) is derived from a virus that originated in Central Africa in chimpanzees and monkeys. Ebola viruses also arose in Central Africa and attack human connective tissues. SARS, severe acute respiratory syndrome, originated from a virus that infects the Chinese horseshoe bat. West Nile virus is a mosquito-borne virus that is common among birds. © McGraw Hill, LLC 20  16.3 Structure of Viruses 3 COVID-19, a close relative of SARS, appeared in China in late 2019 and quickly spread around the world leading to a world-wide pandemic. COVID-19 attacks the upper and lower respiratory tracks. Within a year, there were more than 120 million confirmed COVID-19 cases worldwide and over 2.6 million deaths. The RNA genome of this new virus was 96.1% identical to a bat virus, making it likely that, like SARS, COVID-19 originated in the bats that are common across Asia. © McGraw Hill, LLC 21  16.4 How Viruses Infect Organisms 1 Bacteriophages are viruses that infect bacteria. Structurally and functionally diverse Infection by a T4 bacteriophage involves. The tail fibers attach to the surface of the bacterium. The tail tube pierces the bacterial cell wall. The contents of the head, mostly DNA, are injected into the bacterial cytoplasm. The viral DNA is transcribed and translated by the bacterial cell. New viral components are assembled. Host cell ruptures, releasing new viral cells to infect other bacterial cells. © McGraw Hill, LLC 22  Figure 16.5: A T4 bacteriophage (a) Department of Microbiology, Biozentrum, University of Basel/Science Source Access the text alternative for slide images. © McGraw Hill, LLC 23  16.4 How Viruses Infect Organisms 2 Animal viruses: Enter animal cell by membrane fusion or endocytosis On the surface of animal viruses are spikes which match animal cell surface markers and trigger membrane fusion. Inside the animal cell, the virus sheds its protective coat and replicates its DNA or RNA in the cytoplasm. New viruses produced in the animal cell exit by bursting through the plasma membrane and killing the animal cell. © McGraw Hill, LLC 24  16.5 General Biology of Protists 1 The only unifying thing about protists is that they are not fungi, plants, or animals. Otherwise, they are extremely variable eukaryotes. Protists have varied types of cell surfaces. All have a cell membrane but many have cell walls or glass shells. Movement in protists is accomplished by diverse mechanisms. Cilia, flagella, pseudopods, or gliding mechanisms. © McGraw Hill, LLC 25  16.5 General Biology of Protists 2 Some protists can survive harsh environmental conditions by forming cysts. Cysts are dormant forms of cells with a resistant outer covering in which cell metabolism is more or less completely shut down. © McGraw Hill, LLC 26  16.5 General Biology of Protists 3 Protists employ every form of nutritional acquisition except chemoautotrophy. Phototrophs are photosynthetic autotrophs. Heterotrophic forms include: Phagotrophs ingest visible particles of food. The ingested food is put into intracellular vesicles called food vacuoles that are then broken down by lysosomes. Osmotrophs ingest food in soluble form. © McGraw Hill, LLC 27  16.5 General Biology of Protists 4 Protists typically reproduce asexually, most reproducing sexually only in times of stress. Fission and budding are common forms of asexual reproduction. Sexual reproduction occurs only rarely by exchanging nuclei. © McGraw Hill, LLC 28  Figure 16.7: Reproduction among paramecia: (a) asexual reproduction; (b) sexual reproduction (a) Ed Reschke/Peter Arnold/Getty Images; (b) Ed Reschke/Photolibrary/Getty Images © McGraw Hill, LLC 29  16.5 General Biology of Protists 5 The evolution of multicellularity The key advantage to multicellularity is that it allows for specialization of cells. Some protists form colonial assemblies. the activities of individual cells are coordinated. Multicellularity has evolved in three groups of protists: the brown algae, green algae, and red algae. © McGraw Hill, LLC 30  Figure 16.8: A colonial protist Stephen Durr © McGraw Hill, LLC 31  16.6 Kinds of Protists The protists are the most diverse of the four kingdoms in the domain Eukarya. There are about 200,000 different forms, including many unicellular, colonial, and multicellular groups. Although protists are currently grouped into one kingdom, it is an artificial grouping. Some types of protists can cause serious diseases in humans, such as malaria; many others have industrial applications. © McGraw Hill, LLC 32  Figure 16.9: An amoeba De Agostini Picture Library/Science Source © McGraw Hill, LLC 33  16.7 A Fungus Is Not a Plant 1 Fungi lack chlorophyll and resemble plants only because of their general appearance and lack of mobility. Fungi differ from plants in significant ways, fungi Are heterotrophs. Have filamentous bodies. Have nonmotile sperm. Have cell walls made of chitin. Have nuclear mitosis. © McGraw Hill, LLC 34  Figure 16.11: Mushrooms (a) Robert Marien/Corbis/Getty Images; (b) Ro-ma Stock Photography/Corbis/Getty Images © McGraw Hill, LLC 35  16.7 A Fungus Is Not a Plant 2 Fungi exist mainly in the form of slender filaments called hyphae (singular, hypha). Different hyphae then associate with each other to form much larger structures. A mass of hyphae is called a mycelium (plural, mycelia). Fungal cells are able to exhibit a high degree of communication within a mycelium. Cytoplasm is able to cross between adjacent hyphal cells by a process called cytoplasmic streaming. Multiple nuclei can be connected through the shared cytoplasm. © McGraw Hill, LLC 36  16.7 A Fungus Is Not a Plant 3 Fungi reproduce both asexually and sexually. Spores are a common means of asexual reproduction. In sexual reproduction, hyphae of two different mating types come together. © McGraw Hill, LLC 37  Figure 16.12: Sexual reproduction in fungi © McGraw Hill, LLC 38  Figure 16.13: Many fungi produce spores RF Company/Alamy Stock Photo © McGraw Hill, LLC 39  16.7 A Fungus Is Not a Plant All fungi are heterotrophs and externally digest food by secreting enzymes into their surroundings and then absorbing the nutrients back into the fungus. Some fungi are predatory, such as the oyster mushroom. © McGraw Hill, LLC 40  Figure 16.14: The oyster mushroom L. West/Science Source © McGraw Hill, LLC 41  16.8 Kinds of Fungi 1 There are nearly 74,000 described species of fungi. Traditionally, fungi were classified based on their mode of sexual reproduction. The imperfect fungi, are fungi in which sexual reproduction has not been observed. Eight fungal phyla are now recognized based on genome sequence data. © McGraw Hill, LLC 42  16.8 Kinds of Fungi 2 Together with bacteria, fungi are the principal decomposers in the biosphere. Fungi often act as disease causing organisms for both plants and animals. Fungi are the most harmful pests of living plants as well as stored food products. Many fungi are used commercially, such as for making bread rise, producing alcohol in beverages, or imparting special flavors to cheese. Many antibiotics are derived from fungi. © McGraw Hill, LLC 43  16.8 Kinds of Fungi 3 Two kinds of mutualistic associations between fungi and autotrophic organisms are ecologically important. Mycorrhizae are fungal/plant associations. These interactions increase absorption through the roots of essential nutrients, such as phosphorus. Lichens are fungal/algal or fungal/cyanobacterial associations. Can grow in harsh habitats, such as bare rock. In each of these associations, a photosynthetic organism fixes atmospheric CO2 and makes organic material available to fungi. © McGraw Hill, LLC 44