Name _____________________________________________________ Test Date ____________

UNIT XI – VIRUSES & CLASSIFICATIONI. VIRUSES

Living or non-living?o Lack a _cell membrane______o Do not contain _enzymes____ for _metabolism_o Lack _ribosomes____ for protein synthesiso Do contain _genetic material_____o _Reproduce_____, although they require a _host____ cell

Typically referred to as a _particle____ or _virion__.

A. Structure of Viruses

The following structures are found in all viruses: Genetic Material – The genome of a virus may be either _DNA___ or _RNA___, but never

both. It can be _single-stranded____ or _double-stranded__, _circular___ or _linear__. Protein Coat – The DNA or RNA is surrounded by a protein coat called a capsid. The proteins

making up the capsid are known as _capsomeres_____ and play an important role in the _pathogenicity________ of the virus. In addition, the capsid has _carbohydrate___ ID tags known as _glycoproteins____ which can _mutate____ to enable the virus to escape detection by a host cell’s immune system.

The following additional structures may be present: Viral Envelope – Many viruses have an outer membrane known as an envelope. A viral

particle “steals” the components for its envelope from the host cell membrane, so a viral envelope is primarily composed of _phospholipids___. It aids in the attachment of the virus to the host cell, but a virus enclosed by an envelope is also more sensitive to _drying___. Examples of viruses with envelopes are _HIV, flu virus, cold virus_________.

Tail Fibers – Viruses that infect _bacteria_____ are known as _bacteriophages____. They have “tail fibers” to aid in attachment.

B. Host Range The host range of a virus is the range of host cells that it can infect. It is based on a complementary fit between viral _glycoproteins____ and receptor _proteins___ on the host cell membrane.

Some viruses have broad host ranges which can include several species; for example, swine flu and rabies

Some viruses have narrow host ranges where they infect only a single species; for example, the _bacteriophage___________________ that attacks E. coli.

Some viruses only infect a particular type of tissue or cell within a single species; for example the human cold virus infects only cells of the _upper respiratory tract______; HIV binds to receptors on certain _white blood cells_____.

C. Viral Replication A virus can infect a host cell and use it for reproduction in two ways:

Lytic Infection – _Symptomatic____ cycle in which virus _destroys_____ host cell DNA. Examples are _cold, flu, rabies, measles, etc … most viruses!_______

Lysogenic Infection – _Asymptomatic________ cycle in which viral DNA is incorporated into _host cell DNA_______. Examples are _HIV, chicken pox virus_____.

There are two initial steps that are common to all types of viral infections:1) Virus attaches to _cell membrane_____ of _host ____ cell.2) Virus releases _genetic material__________ into cell, either by _entering cell, typically

through endocytosis___ or _injecting___ genetic material into it.

_Lytic__ Cycle

_Lysogenic____ Cycle

D. Viruses and Disease All viruses are _parasites_____, meaning they require a living host and they cause harm to that host.

1. Herpesvirus – Group of viruses that are _ubiquitous__ and have many forms. Results in lifelong infections, although virus can move back and forth from _lytic___ to _lysogenic__ cycle. Group includes viruses that cause cold sores, chicken pox, genital warts, shingles, and mononucleosis.2. HIV - _Human Immunodeficiency Virus____ – Affects _white__ blood cells(called Helper T

cells) and immune system. The HIV virus is a _retrovirus_____. Retroviruses contain _RNA__ and the enzyme, _reverse transcriptase__ which allows the viral RNA to be _reverse-transcribed____ into _DNA___. Initial symptoms are flu-like, then virus enters _lysogenic____ cycle and replicates in lymph nodes, sometimes for years. When the HIV virus becomes active, it causes _AIDS____- Acquired ImmunoDeficiency Syndrome. Death of the patient results from _secondary infections; breakdown of immune system _______.

3. Human Papilloma Virus – Diverse group of DNA viruses; common cause of skin warts. Danger comes from group of sexually-transmitted HPV which can cause genital warts, but more seriously, _cervical cancer_____. Controversial _vaccine_____ has been produced; effective against most types of sexually-transmitted HPV.

4. Other viral diseases – hepatitis, influenza, smallpox, measles, common cold, rabies, Ebola

II. BIOLOGICAL CLASSIFICATION

Classification is the grouping of objects or organisms based on their similarities. Scientists classify organisms to organize them; make it easier to understand and communicate about them. The branch of biology concerned with the grouping and naming of organisms is called taxonomy. Taxonomy utilizes evolutionary relationships between organisms to correctly identify and group them.

A. Early Taxonomists1. Aristotle – first taxonomist; organized living things into _plants___ & __animals__. Subdivided according to their __ habitat – land, sea, or air dwellers ____.

2. John Ray - a _ botanist ___; first used __ Latin __ for naming organisms. 3. Carolus Linnaeus – classified organisms according to their __ structure __; called the “Father of Taxonomy”; developed the modern system of naming known as _ binomial nomenclature _. Binomial nomenclature is the universal classification system used today in which groups are formed according to _Physical characteristics __ and then each organism is assigned a 2- word scientific name. The scientific name is the _ genus _ and __ species _ of the organism. The genus and species names are always __ underlined _ or written in _ italices _. _Genus__ is capitalized, _species_ is not.

B. Categories of Classification 1. Kingdom – broadest category, groups of closely related phyla 2. Phylum – groups of closely related classes 3. Class – groups of closely related orders 4. Order – groups of closely related families 5. Family – groups of closely related genera 6. Genus – groups of closely related species 7. species – smallest and most similar group; organisms that share specific characteristics and can interbreed.

Confusion in Using Different LanguagesLatin Names are Understood by all Taxonomists

Which two are more closely related?

Grizzly Bear Ursus arctos

C. Scientific Classification of a Human Kingdom ______Animalia_______ Phylum _______Chordata______ Class _________Mammalia_____ Order _________Primate_______ Family ________Hominidae____ Genus ________Homo _ ______ Species _______sapiens_______

III. THE EVOLUTION OF CLASSIFICATION Taxonomy, the science of classification, is a work in progress, in large part,

because of evolution, both as a science and a process. A. Evolution As A Science – As the study of evolution becomes more sophisticated due to DNA sequencing, scientists are realizing that organisms, or entire groups of organisms, have been incorrectly classified, or assigned to the wrong classification levels

1. The Kingdoms of Life DNA analysis has had a major impact on the classification system, changing the long accepted system of 5 kingdoms to 6 kingdoms. The two prokaryotic kingdoms, Archaebacteria and Eubacteria were originally classified together as Kingdom Monera.

2. The Three Domains of Life Recently, further studies have led taxonomists to propose a classification system which includes three “super-kingdoms” called Domains. a. Domain Archaea – Includes the Archaebacteria

b. Domain Bacteria – Includes all remaining prokaryotes or the Eubacteria

c. Domain Eukarya – Includes the four eukaryotic kingdoms – Protista, Fungi, Plantae, Animalia

II. THE SIX KINGDOMS OF LIFE

A. Kingdom Archaebacteria 1. Cell Type – Prokaryotic 2. Cell Structure - cell wall without peptidoglycan ; DNA, cytosol, cell membrane , & ribosomes present 3. Body Form - All unicellular 4. Nutrition - autotrophic or heterotrophic 5. Other characteristics – considered to be the most ancient of organisms; live in very harsh conditions like extreme temperatures, high pH concentration, etc. Another group of Archaebacteria live in the digestive system of animals and produce methane gas. 6. Examples - methanogens, Thermoacidophiles, Halophiles

Great Salt Lake, UT - The Great Salt Lake, second Picture above is of the hot springs in in salinity only to the Dead Sea, was believed to be Yellowstone Park - Archaebacteriaas 'dead' until very recently. However, halophilic microorganisms strive in these environments having developed mechanisms to endure high salt concentrations, dessication and constant UV radiation.

B. Kingdom Eubacteria 1. Cell Type - Prokaryotic 2. Cell Structure - Cell wall made up of peptidoglycan ; DNA, cell membrane , cytosol, & ribosomes present 3. Body Form - All Unicellular 4. Nutrition – Mostly heterotrophic; some are autotrophic (photosynthetic or chemosynthetic)

5. Other characteristics – Most common bacteria. They are ubiquitous which means they are found everywhere . Very important decomposers. Some are pathogenic, but most are harmless .6. Examples - decomposers, E.coli, Streptococcus sp, Staphylococcus sp , Salmonella sp

C. Kingdom Protista

1. Cell Type - Eukaryotic 2. Cell Structure – May have cell wall; may have chloroplasts; may be motile and have cilia or flagella. 3. Body Form – Mostly unicellular; may be multicellular 4. Nutrition – autotrophic or heterotrophic 5. Other Characteristics – Nicknamed “ Catch-all” kingdom or “Junk- Drawer”. Contains organisms that don’t “fit” into other kingdoms. Protists are sub-grouped according to which Eukaryotic kingdom they’re most like; for example. Fungi-like, Protist-like, or Animal-like.

7. Examples – slime molds, Euglena, Paramecium, algae, Amoeba

D. Kingdom Fungi 1. Cell Type - Eukaryotic

2. Cell Structure – Have cell wall made of chitin; fungi do NOT have chloroplasts. 3. Body Form – Mostly multicellular; may be unicellular. Single-celled fungi are known as yeast.

4. Nutrition – All heterotrophic! Obtain nutrients through a process called absorption, meaning food is digested outside their bodies by secretion of cells, then absorbed by fungi. 5. Other Characteristics – Principle decomposers. Also important in brewing and baking. 6. Examples – mushrooms, molds, yeasts, truffles, morels

E. Kingdom Plantae 1. Cell Type - Eukaryotic 2. Cell Structure – Have cell wall made of cellulose; chloroplasts present. 3. Body Form – All multicellular

4. Nutrition – All autotrophic 5. Other Characteristics – Most contain organs and organ systems. All non-motile with specialized reproductive structures.

5. Examples – mosses, ferns, trees, flowering plants

F. Kingdom Animalia 1. Cell Type - Eukaryotic 2. Cell Structure – Never have cell wall 3. Body Form – All multicellular 4. Nutrition – All heterotrophic 5. Other Characteristics – Most complex of all kingdoms. Most organisms contain organs and organ systems. All members are capable of movement sometime during their lifetime. Most animals are invertebrates meaning they lack a backbone. All vertebrates belong to Phylum Chordata.

6. Examples – sponges, fish, worms, insects, reptiles, amphibians, mammals