Exam 1: Viruses, Bacteria & Archaea, Protists, Fungi Flashcards
taxonomy
the practice and study of classification of things or concepts + the principles that underlie such classification OR putting things into diff categories as a means of organization
two main schools of thought
lumpers - group critters into as few groups as possible
splitters - split critters into as many groups as possible
taxonomic hierarchy
domain kingdom phylum class order family genus species
dumb king philip can only find green socks
taxa
a group of critters at a given taxonomic level
species
a group of like critters that can reproduce and produce viable offspring
classification systems/historic people
aristotle - 4th century greek philospher, grouped into plants and animals, divided animals into blood and bloodless, divided animals into movement with flying, walking, and swimming system used until mid 1600s
Linnaeus 18th century created binomial nomenclature
Charles Darwin in 19th century, theory of evolution/adaptation “the origin of species”
phylogeny
the evolutionary development and history of a species or higher taxonomic grouping of organisms
OR
the taxonomic classification mirroring the evolutionary development
cladistics
tries to show evolutionary relationships based on physical traits shared by different groups of organisms
15.1 Viruses are Infectious Particles of Genetic Info + Protein
a. smaller and simpler than cells (12x smaller than bacterium)
- all viruses have genetic info + protein coat (capsid)
some may have an envelope
B. host range consists of the organism it infects
- can enter only a cell that has a specific receptor
all species get viral infections
reservoir of a virus is the site where it exists in nature
C. Are viruses alive>
- most do not consider them to be
- don’t metabolize, respond to stimuli, or reproduce on their own
- do have genetic material and mutate -> natural selection
- not part of taxonomic hierarchy, instead grouped by chemical similarities
15.2 Viral replication occurs in 5 stages
- attachment
- penetration
- synthesis
- assembly
- release
amount of time varies
draw and label all 5 steps of viral replication within a cell
refer to figure 15.2 in notes/lect slides
15.3 cell death may be immediate or delayed
A. some viruses kill cells immediately
- lytic infection/pathway
- virus enters cell + immediately replicates and lyses host
- “phage therapy” for bacterial infections - unlikely to acquire resistance, targeted to specific bacteria, studied by USSR
essentially viruses that selectively target bacteria
B. Viral DNA may also hide in a cell
- lysogenic infection/pathway
- genetic material of a virus is replicated along with the host cells chromosome
- prophage
- host not immediately destroyed
- can also switch to lytic pathway
15.4 Effects of a Viral infection may be mild or severe
A. Symptoms may result from cell death + immune response
- incubation period = the time between exposure to disease agent and disease signs and or sympyoms
- influenza virus -> flu
- dead + damaged cells in airway cause the respiratory symptoms of influenza -> cough + sore throat
- fever + body aches caused by cytokines released by immune systems
B. some animal viruses linger for year
- latent infection does not produce disease symptoms
- viral genetic info inside cell
- herpes simplex virus type I
- cold sores on lips, stressed cells release viruses that infect other cells, cold sore localized death of these cells
- HIV
- retrovirus - uses reverse transcriptase
- RNA genome
- infects helper T cells
- loss of these cells leads to AIDS
- Human papillomavirus causes cervical cancer by signaling host cell to divide continuously
C. Drugs and Vaccines help fight viral infections
- some antiviral drugs interfere with enzymes or other proteins that are unique to viruses
few medicines inhibit viruses without killing infected host cells
complicated by genetic variability by viruses
vaccination teaches immune system to recognize virus
childhood vaccinations greatly reduced or eliminated viral infections
fertilized chicken eggs used to produce viruses
epidemic, pandemic, and endemic
more cases of disease than expected
widespread, worldwide epidemic
disease outbreak that is consistently present
HIV
human immunodeficiency virus
AIDS
acquired immunodeficiency syndrome
origin of HIV
raw bushmeat (monkeys), origin in SF LGBTQ+ community
15.5 Viruses Cause Diseases in Plants
- first virus ever discovered was tobacco mosaic virus
- most spread by plant-eating insects
- spread through plasmodesmata
- can use post-transcriptional gene silencing to fight off infections
Rabies
Rabies is a viral disease that causes acute inflammation of the brain in humans and other mammals
incubation period typically 1-3 months
infection via animal bites
- hydrophobia - difficulty swallowing
99.99+ % fatal (<6 human survival cases EVER, 4 in last 5 years)
Vaccine is very effective if given early enough
US human (fatal) cases 1-3/year
Ebola
Originated in central africa - blood vessels break down, internal bleeding, extreme bleeding and ultimately death
zika virus
mosquito-transmitted; (RNA)
associated with microcephaly (mechanism unknown)
- mild to significant learning disabilities
- impaired motor functions
- difficulty with movement and balance
- speech delays
first isolated in uganda in the zika forrest - 1947
brazil 2015 - 3.500 cases (47 fatal)
15.6 Viroids and Prions are other noncellular infectious agents
A. A Viroid is an infectious RNA molecule
- naked RNA
- does not encode proteins
- interferes with ability to produce proteins
B. A prion is an infectious protein
- abnormal form causes brain cells to die
- spongiform encephalopathies
- mad cow disease (BSE)
- human forms
- kuru - cannibalism
- creutzfield-Jakob disease (CJD)
- fatal familial insomnia
monkeypox + smallpox
within 1-3 days after appearance, patient develops rash, often beginning on the face then spreading
illness typically lasts 2-4 weeks
monkeypox disovered 1958 in africa, dna virus, mortality <10%
presents like chicken pox and mild smallpox
cross-immunity with smallpox
smallpox - 30% fatality, successful vaccine in 1797, completely eradicated in 1977, still exists in labs
16.1 Prokaryotes are a biological success story
Prokaryote
- single celled organism that lacks a nucleus and membrane-bounded organelles
2 prokaryotic domains
- bacteria
- archaea
