Classification Bacteria Viruses Unit 7 Chapter 17 Organizing
Classification, Bacteria, & Viruses Unit 7
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Early Systems of Classification § Biologists use a system of classification to organize information about living things.
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Aristotle’s System § Aristotle classified organisms as either animals or plants.
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Linnaeus’s System § Linnaeus’s system of classification was the first formal system of taxonomy. Perching bird Bird of prey Wading bird
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Binomial Nomenclature § Linnaeus’s method of naming organisms, called binomial nomenclature, gives each species a scientific name with two parts. § The first part is the genus name, and the second part is the species. §Ex. Ursus americanus
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification § Biologists use scientific names for species because common names vary in different areas of the world. Ursus americanus American black bear
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification § When writing a scientific name, scientists use these rules: § The first letter of the genus name always is capitalized, but the rest of the genus name and all letters of the species are lowercase. § If a scientific name is written in a printed book or magazine, it should be italicized. § When a scientific name is written by hand, both parts of the name should be underlined. § After the scientific name has been written completely, the genus name will be abbreviated to the first letter in later appearances (e. g. , C. cardinalis).
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Taxonomic Categories § The taxonomic categories are part of a hierarchal system. § Each category is contained within another, and they are arranged from broadest to most specific.
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Species and Genus § A named group of organisms is called a taxa. § A genus is a group of species that are closely related and share a common ancestor.
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Family § A family is the next higher taxon, consisting of similar, related genera.
Chapter 17 Organizing Life’s Diversity 17. 1 The History of Classification Higher Taxa § An order contains related families. § A class contains related orders. § A phylum contains related classes. § The taxon of related phyla or divisions is a kingdom. § The domain is the broadest of all the taxa and contains one or more kingdoms.
Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake Sea star KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Typological Species Concept § Aristotle and Linnaeus thought of each species as a distinctly different group of organisms based on physical similarities.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Biological Species Concept § The biological species concept a species as a group of organisms that is able to interbreed and produce fertile offspring in a natural setting.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Phylogenic Species Concept § Phylogeny is the evolutionary history of a species. § The phylogenic species concept shows evidence of a pattern of ancestry and descent.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Morphological Characters § Shared morphological characters suggest that species are related closely and evolved from a recent common ancestor. § Analogous characters the same function but different underlying construction. § Homologous characters different functions, but show an anatomical similarity inherited from a common ancestor.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Biochemical Characters § Scientists use biochemical characters, such as amino acids and nucleotides, to help them determine evolutionary relationships among species. § DNA and RNA analyses are powerful tools for reconstructing phylogenies.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Phylogenetic Reconstruction § Cladistics reconstructs phylogenies based on shared characters. § Scientists consider two main types of characters when doing cladistic analysis. § An ancestral character is found within the entire line of descent of a group of organisms. § Derived characters are present members of one group of the line but not in the common ancestor.
Chapter 17 Organizing Life’s Diversity 17. 2 Modern Classification Cladograms § The greater the number of derived characters shared by groups, the more recently the groups share a common ancestor.
Section 18 -2 Traditional Classification Versus Cladogram Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Barnacle Gastropod Limpet Molted exoskeleton Segmentation CLASSIFICATION BASED ON VISIBLE SIMILARITIES Tiny free-swimming larva CLADOGRAM
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Grouping Species § The three domains are Bacteria, Archaea, and Eukarya. § The six kingdoms are Bacteria, Archaea, Protists, Fungi, Plantae, and Animalia.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Domain Bacteria § Eubacteria are prokaryotes whose cell walls contain peptidoglycan.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Domain Archaea § Archaea are thought to be more ancient than bacteria and yet more closely related to our eukaryote ancestors. § They are called extremophiles because they can live in extreme environments.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Domain Eukarya § All eukaryotes are classified in Domain Eukarya. § Domain Eukarya contains Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Kingdom Protista § Protists are eukaryotic organisms that can be unicellular, colonial, or multicellular. § Protists are classified into three different groups— plantlike, animallike, and funguslike.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Kingdom Fungi § A fungus is a unicellular or multicellular eukaryote that absorbs nutrients from organic materials in its environment. § Member of Kingdom Fungi are heterotrophic, lack motility, and have cell walls.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Kingdom Plantae § Members of Kingdom Plantae form the base of all terrestrial habitats. § All plants are multicellular and have cell walls composed of cellulose. § Most plants are autotrophs, but some are heterotrophic.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms Kingdom Animalia § All animals are heterotrophic, multicellular eukaryotes. § Animal organs often are organized into complex organ systems. § They live in the water, on land, and in the air.
Chapter 17 Organizing Life’s Diversity 17. 3 Domains and Kingdoms
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Diversity of Prokaryotes § Bacteria are microscopic organisms that are prokaryotes. § Prokaryotes are divided into two domains—the Domain Bacteria (eubacteria) and the Domain Archaea (archaebacteria).
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Photosynthetic eubacteria Archaebacteria Eubacteria magnification unavailable 9560 x 3000 x
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Eubacteria § Very strong cell walls § Contain peptidoglycan § Some have a second cell wall
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Archaebacteria § Thermoacidophiles (thur muh uh SIH duh filz) live in hot, acidic environments. § Halophiles (HA luh filz) live in very salty environments. § Methanogens (meh THAHN oh jenz) cannot live in the presence of oxygen.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Differences Between Eubacteria and Archaebacteria § The cell walls of the eubacteria contain peptidoglycan, but the cell walls of archaebacteria do not. § The two groups of organisms have different lipids in their plasma membranes. § Different ribosomal proteins and RNA
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Prokaryote Structure § Prokaryotes are microscopic, unicellular organisms. § They have some characteristics of all cells, such as DNA and ribosomes. § Lack a nuclear membrane and other membrane-bound organelles
Chapter 18 Bacteria and Viruses 18. 1 Bacteria § Chromosomes § Capsule § Pili § Size
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Identifying Prokaryotes § Shape § Spherical = Cocci § Rod-shaped = Bacilli § Spiral-shaped = Spirochetes Bacilli Cocci 400 x 5460 x 2000 x
Identified by shape, cell wall, method of movement, and how they obtain food • Shapes – • Bacilli = rod • Cocci – round • Spirilla – spiral • Prefixes – strep = long chains, staph = clumps, diplo = pairs
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Cell Walls § Eubacterial cells have peptidoglycan. § Dyes added to the bacteria identify those with and those without an outer layer of lipid. Purple = gram positive cell wall contains peptidoglycan
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Movement § Prokaryotic flagella are made of filaments. § Flagella help prokaryotes to move toward materials that they need to survive.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Reproduction of Prokaryotes § Binary Fission § Division of a cell into two genetically identical cells § Conjugation § Two prokaryotes attach to each other and exchange genetic information.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Photoautotrophs § Carry out photosynthesis in a similar manner as plants Chemoautotrophs § Break down and release inorganic compounds that contain nitrogen or sulfur Aerobes and Anaerobes § Obligate aerobes are bacteria that require oxygen to grow. § Anaerobic bacteria do not use oxygen for growth or metabolism.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Survival of Bacteria § Endospores § Resistant to harsh environments and might be able to survive extreme heat, extreme cold, dehydration, and large amounts of ultraviolet radiation
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Mutations § Bacteria reproduce quickly and their population grows rapidly. § Mutations lead to new forms of genes, new gene combinations, new characteristics, and genetic diversity.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Ecology of Bacteria § Nutrient cycling and nitrogen fixation § Bacteria are decomposers, returning vital nutrients to the environment. § Nitrogen-fixing bacteria live in a symbiotic relationship in the root nodules of plants such as soybeans, clover, and alfalfa.
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Normal Flora § Most of the bacteria that live in or on you are harmless and are called normal flora. 21, 674 x E. coli
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Foods and Medicines § Some foods are made with the aid of bacteria. § cheese § yogurt § buttermilk § pickles § vitamins
Chapter 18 Bacteria and Viruses 18. 1 Bacteria Disease-causing Bacteria § A small percentage of bacteria cause disease. § Bacteria multiply quickly at the site of infection. § Bacteria secrete a toxin.
Chapter 18 Bacteria and Viruses 18. 2 Viruses and Prions Viruses § A nonliving strand of genetic material within a protein coat § No organelles to take in nutrients or use energy § Cannot make proteins § Cannot move § Cannot replicate on their own
Chapter 18 Bacteria and Viruses 18. 2 Viruses and Prions Viral Infection § In order to replicate, a virus must enter a host cell. § The virus attaches to the host cell using specific receptors on the plasma membrane. § Many viruses cannot be transmitted between different species.
Chapter 18 Bacteria and Viruses 18. 2 Viruses and Prions Lytic Cycle § The host cell makes many copies of the viral RNA or DNA. Lysogenic Cycle § Viral DNA inserts, or integrates into a chromosome in a host cell. § Infected cell will have the viral genes permanently.
Chapter 18 Bacteria and Viruses 18. 2 Viruses and Prions
Chapter 18 Bacteria and Viruses 18. 2 Viruses and Prions Retroviruses § Viruses that have RNA instead of DNA for their genetic material § Retroviruses have a protein capsid. § Lipid envelope is obtained from the plasma membrane of a host cell
Chapter 19 Protists 19. 1 Introduction to Protists § All protists are eukaryotes. § Some reproduce asexually by mitosis while others exchange genetic material during meiosis.
Chapter 19 Protists 19. 1 Introduction to Protists Classifying Protists § Some scientists classify protists by their methods of obtaining nutrition. § Animal-like protists § Plantlike protists § Funguslike protists
Chapter 20 Fungi 20. 1 Introduction to Fungi Major Features of Fungi § Cell wall composed of chitin § Hyphae form a netlike mass called a mycelium. § Hyphae provide a larger surface area for nutrient absorption.
Chapter 20 Fungi 20. 1 Introduction to Fungi Spore Production § The asexual and sexual life cycle of most fungi includes spore production. § A spore develops into a new organism without the fusion of gametes. § Spores produce new hyphae that form a mycelium.
Chapter 21 Introduction to Plants 21. 1 Plant Evolution and Adaptations Stomata § Enable the exchange of gases on a plant § Openings in the outer cell layer of leaves and some stems
Chapter 21 Introduction to Plants 21. 1 Plant Evolution and Adaptations Vascular Tissues § Vascular tissue enables faster movement of substances than by osmosis and diffusion, and over greater distances. § Vascular tissue provides support and structure, so vascular plants can grow larger than nonvascular plants.
Chapter 21 Introduction to Plants 21. 1 Plant Evolution and Adaptations Seeds § A plant structure that contains an embryo, contains nutrients for the embryo, and is covered with a protective coat § These features enable seeds to survive harsh environmental conditions and then sprout when favorable conditions exist.
Chapter 22 Plant Structure and Function 22. 1 Plant Cells and Tissues Vascular Tissue § Xylem § Transports substances away from the roots § Composed of specialized cells called vessel elements and tracheids
Chapter 22 Plant Structure and Function 22. 1 Plant Cells and Tissues Phloem § Transports dissolved sugars and other organic compounds throughout the plant.
Chapter 23 Reproduction in Plants 23. 2 Flowers Flower Organs
Chapter 24 Introduction to Animals 24. 1 Animal Characteristics Support § Invertebrates § Exoskeletons § Hard or tough outer coverings that provide a framework of support
Chapter 24 Introduction to Animals 24. 1 Animal Characteristics Support § Vertebrates § Endoskeletons § Provide support for the body § Provide an internal brace for muscles to pull against
Chapter 24 Introduction to Animals 24. 2 Animal Body Plans Symmetry § Similarity or balance among body structures of organisms § Asymmetry § Radial symmetry § Bilateral symmetry
Kingdom Protista Ch. 20 -1 and 2
What is a protist? • Eukaryotes that don’t fit in the other kingdoms • Very diverse kingdom – 200, 000 species • Most are unicellular • Protist = “the very first” – first eukaryotes on earth • 3 main groups based on how they obtain food
Animal-like protists • Heterotrophs • “protozoans” = first animals • 4 phyla (groups) based on mode of movement
Zooflagellates • Swim with use of flagella • Flagella – long whip-like projection used to propel an organism • Live in lakes and streams • Absorb food through cell membrane • Reproduce asexually through binary fission • i. e. euglena
Sarcodines • Move and feed through use of pseudopods • Pseudopod – temporary projection of the cytoplasm • i. e. Amoebas • When feeding, they surround food and bring into cell in the form of a food vacuole
Ciliates • Use cilia for feeding and movement • Cilia – hair-like projections that flow back and forth like ores • i. e. Paramecium • Contain macro (working copy) and micronucleus (reserve copy of genetic info) • Food is swept into the gullet where it is forced into food vacuoles
Sporozoans • Don’t move on their own and are parasites Malaria sporozoite
Zooflagellates and disease • Malaria – effects 300 -500 million people – Caused by the sporozoan Plasmodium – Carried by the female Anopheles mosquito – Infection cycle – mosquito bites human, saliva and plasmodium sporozites enter blood, plasmodium infects liver and red blood cells, red blood cells burst dumping toxins into bloodstream
• African sleeping sickness – – Caused by zooflagellate Trypanosoma – Spread by the bite of the Tsetse fly – Effects the nervous system causing loss of consciousness and coma • Amebic dysentery – – Caused by Entamoeba in contaminated water
Kingdom Fungi Ch. 21
What are fungi? • Eukaryotic heterotrophs that have cell walls made of chitin • Chitin – complex carbohydrate • Digest food outside their bodies and absorb the nutrients • Some absorb from decaying matter others are parasites and absorb from a host
Fungi structure and function • All but yeasts are multicellular • Hyphae – tiny filaments in the fungi made of 1 cell • Mycelium- many hyphae tangled together in a mass underground • Fruiting body – reproductive structure above ground • Often clusters of fruiting bodies belong to same mycelium Fruiting body hyphae mycellium
Fungi reproduction • Asexually and sexually • Asexual – – parts of hyphae break off and grow on their own – Spores – released from sporangiophores into the air and will settle and grow on their own – Fungi spread by spores, spores grown when environmental conditions are right • Sexual – two hyphae (+ and -) meet and form a gamete
Figure 21 -5 The Life Cycle of Rhizopus Section 21 -2 Zygospore (2 N) FERTILIZATION Sporangium Gametangia MEIOSIS Sporangium Spores (N) Zygospore (2 N) Spores (N) Stolons + Mating type (N) - Mating type (N) Sporangiophore Asexual Reproduction Rhizoids Sexual Reproduction Diploid Haploid
How are fungi classified? • According to structure and method of reproduction • 4 groups – Common Molds - Grow on meat, cheese, and breads – Sac Fungi – larges phylum, yeasts – Club Fungi – club shaped cap to mushroom, some edible but many are poisonous – Imperfect fungi – fungi that don’t fit in any other phylum (penicillium)
Kingdom Plantae Chapter 22
What are plants? • Multi-cellular eukaryotes • Cell walls made of cellulose. • Develop from multi-cellular embryos • Carry out photosynthesis using green pigments chlorophyll a & b
Survival Requirements… • • Sunlight water/minerals gas exchange movement of water and nutrients
Bryophytes • Need water for reproduction • No vascular tissue—water by osmosis – Can move few centimeters above the ground • Small in size • i. e. mosses, liverworts, and hornworts. • adapted to environments with wet habitats and nutrient-poor soils. • No true roots • have rhizoids—long, thin cells – anchor them in the ground – absorb water & minerals from the surrounding soil.
Seedless Vascular Plants • Plants containing vascular tissues – Specialized to conduct water and nutrients through the body of the plant. • True roots, leaves, and stems • i. e. club mosses, horsetails, and ferns. • Developed phloem & xylem
Movement in plants • Xylem – Tissue that carries water upward from the roots to every part of the plant. – Tracheids are the key cells in xylem • Hollow cells with thick cell walls that resist pressure • Phloem – Transports solutions of nutrients and carbs produced by photosynthesis
Seed Plants • Two groups – Gymnosperms – Angiosperms • Gymnosperms – seeds on surface of cones • Angiosperms – i. e. flowering plants – seed within a layer of tissue that protects it. • Reproduce without water!
Angiosperms—Flowering Plants • Reproductive organs: Flowers! – Contain ovaries that surround/protect seeds – Monocots: one seed leaf, or cotyledon • i. e. corn, wheat, lilies, orchids, and palms – Dicots: two seed leaves, or cotyledons • i. e. roses, clover, tomatoes, oaks, and daisies
Parts of Plants • Roots, stems, and leaves – Roots: tap roots & fibrous roots; absorb water, nutrients, minerals; anchor plants – Stems: support plant body, transport nutrients, contains vascular system (made of xylem and phloem) – Leaves: Site of photosynthesis; Absorbs light Tap Root
Plant Responses • Phototropism – Plant movement towards light
Kingdom Animalia Survey of organisms Chs. 26 -32
What is an Animal? • An animal is a multicellular, eukaryotic heterotroph whose cells lack cell walls
How are they classified? • Invertebrates – Animals that have no backbone, or vertebral column. – 95% of animals – i. e. insects, worms, jellyfish, sea stars • Vertebrates – Animals that have a backbone – 5% of animals – i. e. fish, amphibians, reptiles, birds, mammals
Essential Functions • Feeding • Respiration – Oxygen in – Carbon Dioxide out • Circulation – Circulatory system – Diffusion • Excretion – Bi-product of metabolism • Response – Nervous system • Movement – Skeleton & Muscles • Reproduction – Sexual or Asexual Circulatory system or diffusion
Phylum Chordata • What are chordates? – Animal that has for some stage of its life: • • Dorsal (back), hollow nerve cord Pharyngeal slits Post-anal tail A notochord – Most are vertebrates, but not all! • i. e. tunicates, lancelets, sponges
Mammalia • What are they? – Animals that have hair, ability to nourish young (milk), breath air, four-chambered hearts, endotherms. – Endotherm: animal that generates body heat internally – Feeding: herbivores, carnivores, omnivores, filter feeders.
Maintaining Homeostasis • Endothermy – Organism that maintains an internal temperature by generating its own body heat from within • Example? • Ectothermy – Organism that relies on interactions with the environment to help control body temperature • Example?
Unit 7 Ch. 19. 1 -2 Bacteria
Prokaryotes • • • Single cell No true nucleus few organelles Archaebacteria – extreme environments Eubacteria
Eubacteria • Wide variety of bacteria with different lifestyles • Cell wall for protection from injury – also determines the shape of bacteria • E. Coli – lives in mammal intestines
Section 19 -1 The Structure of a Eubacterium Ribosome Peptidoglycan Cell wall membrane Flagellum Go to Section: DNA Pili
Archaebacteria • Cell walls made from different materials than eubacteria • Cell membrane lipids different from eubacteria • DNA sequences are more like eukaryotes than eubacteria • Live in extreme environments like: great salt lake, hot springs, oxygen deprived mud
Identifying prokaryotes • Identified by shape, cell wall, method of movement, and how they obtain food • Shapes – – – Bacilli = rod Cocci – round Spirilla – spiral Prefixes – strep = long chains, staph = clumps, diplo = pairs
Cell walls • Chemical make-up determined by a gram stain (purple or red) – Peptidoglycan = purple, gram positive – Outer layer of lipid and carbohydrates = pink, gram negative
Movement • • Flagella – whip-like structure Snake type movement Move in a slime they secrete Do not move at all
Obtaining energy • Autotrophs – some carry out photosynthesis and others carry out chemosynthesis • Heterotrophs – “eat” food – (food spoilage) • Photoheterotrophs – get energy using both methods above
Releasing energy • Obligate aerobes – carry out cellular respiration with oxygen • Obligate anaerobes – cannot live in presence of oxygen – Clostridium botulinum botulism • Facultative anaerobes – can live with or without oxygen
Growth and Reproduction • Binary fission – DNA replicated and splits in half – asexual • Conjugation – genetic info exchange between cells
Unit 9 Bacteria in Nature
Bacteria’s importance • Vital to living world • Photosynthetic producers putting oxygen into air • Decomposers of dead matter to allow recycling of nutrients
Decomposers • • Break down of dead matter Helps to recycle nutrients in the ecosystem Play an important role in sewage treatment Produces purified water, nitrogen, carbon dioxide gases, and byproducts to be used as fertilizers
Nitrogen fixers • Plants depend on nitrogen to make amino acids and proteins →animals get nitrogen from plant proteins • Nitrogen from atmosphere must be converted to ammonia NH 3 before plants can use it – This is done by “nitrogen-fixing” bacteria – Symbiotic relationship between plants and bacteria - Rhizobium
Bacteria and disease • Pathogens – disease causing agents (small percentage of bacteria) • Treated with antibiotics – block the growth and reproduction of bacteria • Cause disease in two ways – Break down tissue for food • Tuberculosis – Release toxins that harm the body • Food poisoning • Strep throat – scarlet fever = streptococcus Lung infection
Human use for bacteria • Manufacturing food – cheese, buttermilk, yogurt, sour cream • Digesting oil spills • Water treatment • Medicines • warfare Anthrax
Controlling bacteria • Sterilization – destroy bacteria by subjecting them to great heat or chemical action – Disinfectants – chemical solution that kills bacteria – Refrigeration – bacteria grows more slowly in cold temps. – food – Boiling at high temps to kill bacteria – Salt, vinegar, sugar
virus Living or not? 10/29/2020
Virus (latin for poison) • Requires host cell to reproduce-intracellular parasite • Don’t move, respire, or grow – no independent metabolism • smaller than tiniest bacteria • possess either DNA or RNA • may be inactive indefinitey • mutates rapidly • Named for disease caused, organ infected , or region detected in
structure • Contain a nucleic acid and protein • HEAD region – Capsid--protein coat with nucleic acid core • TAIL region – to attach to bacteria/cells
Viral recognition and attachment • Virus must recognize specific receptor site on host cell • Part of virus matches site on host, lands and locks in • Attachment is specific- virus can only enter and reproduce in a few types of cells • I. E. - tobacco mosaic virus cannot infect human cells even though we are exposed to it daily
Figure 19 -9 Virus Structures Section 19 -2 Tobacco Mosaic Virus T 4 Bacteriophage Head DNA Influenza Virus RNA Capsid proteins Capsid RNA Tail sheath Tail fiber Surface proteins Membrane envelope
Reproduction • Must take place inside a host cell • Infection--chance contact • Lytic Infection – – Viral DNA takes over host nucleus, produces new viruses – Lysis of host cell – bursts and dies – new viruses are released
Alternate reproduction • Lysogenic cycle (infection) – virus attacks cell but doesn’t kill immediately • Viral DNA mixes with host DNA = prophage • Doesn’t always reproduce right away, cell may function normally • Viral DNA activates and viral reproduction begins
Figure 19 -10 Lytic and Lysogenic Infections
Figure 19 -11 Viruses and Cells Section 19 -2
Pathogenic viruses • • Ebola zaire-AIDS rhinoviruses influenza measles, mumps, chicken pox polio rabies smallpox
Vaccines • “cow pox”--Edward Jenner – 1796
- Slides: 128
