Exam 1 Flashcards
What are the 6 Kingdoms?
-Bacteria
-Protista
-Archaea
-Plantae
-Fungi
-Animalia
Taxonomy levels LG -> SM:
-Domain
-Kingdom
-Phylum
-Class
-Order
-Family
-Genus
-Species
Divergent evolution:
Two species evolve in different directions from a common ancestor (think darwins finches)
Convergent evolution:
two distantly-related species independently evolve similar phenotypes
Fossils:
-provide record of course of life over time
-shows waxing & waning of biological diversity
Homologous structures
structures with
different appearances and functions that all
derived from the same body part in a
common ancestor
(different functions, same underlying structure. thumb vs paw)
Evidence for evolution:
-Homologous structures
-Adaptation
-Artificial selection
-Vestigial structures
Vestigial structures:
Structures that don’t have an apparent use in the body. (think blind fish w/ eyes, fingernails on sealions, hip bones on snakes)
Ernst Mayr’s biological species concept:
groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups
(species consist of populations whose members repro w/ each other and produce fertile offspring)
Mechanisms of reproductive isolation:
-Temporal isolation
-Ecological isolation
-Geographic isolation
-Behavioral isolation
-Mechanical isolation
-Prevention of gamete fusion
-Protozygotic isolation
Behavioral isolation:
when species are reproductively isolated from others due to differences in behavior. (think red footed vs blue footed booby)
Mechanical isolation
isolation where two species cannot physically undergo fertilization.(think bumblebees & hummingbirds)
Postzygotic isolation:
Prevents normal development into reproducing adults
Hybridization:
mating between two different species with a zygote being formed
Hybrids often:
-Do not develop into adults
-Do not develop into fertile adults
Five elements of evolutionary change (Not in HW-equilibrium):
-Mutation
-Geneflow
-Nonrandom mating
-Genetic drift
-Natural selection
Fitness:
-relative to reproductive success.
-Individuals w/ one phenotype have more surviving offspring than those with an alternative phenotype.
Fitness is a combination of:
-Survival
-Mating success
-# of offspring per mating that survive
-Traits favored in one environment
Natural selection:
environmental conditions determine which individuals in a population produce the most offspring
3 conditions for natural selection:
-Variation in individuals in population
-Variation among said individuals result in the # of surviving offspring
-Variation must be genetically inherited
Stabilizing selection:
favors an average phenotype.
Directional selection:
shifts the range of preferred phenotypes
Disruptive selection:
Selects against the average phenotype and favors the extremes.
Gradualism:
slow, progressive changes over a very long time
Punctuated equilibrium:
brief periods of change with long periods of stability
Adaptive radiation:
closely related species that have recently evolved from a common ancestor by adapting to different parts of the environment
Adaptive radiation occurs:
-occurs through repeated instances of sympatric speciation
-produces suite of species adapted to different habitats
-in an environment w/ few other species & resources (Remote islands, Hawaii/Galapagos)
-Catastrophic event leading to extinction of other species
Hawaiian Drosophila:
The fruit fly in Hawaii that quickly evolved/adapted to the environment as it had many habitats w/ no natural prevention for fruit flies.
-Diversified rapidly, both morphological and behavioral
Systematics of biology:
-All living organisms share many characteristics while still differing substantially from other groups
-Biologists group organisms based on shared phenotypic characteristics & newer molecular sequence data
-Hypothesis about evolutionary relatedness
-Tremendous diversity of life
Phylogenic trees:
a diagram that represents evolutionary relationships among organisms.
Phylogenic tree ROOT:
-Beginning
-indicates that an ancestral lineage gave rise to all organisms on the tree
Phylogenic tree BRANCH POINT:
-Beginning of branch
-A branch point indicates where two lineages diverged.
Phylogenic tree BASAL TAXON:
-End of branch
-A lineage that evolved early and
remains unbranched
Phylogenic tree SISTER TAXA:
-When one branch point shares multiple ends
-When two lineages stem from the same branch point, they
are sister taxa.
Phylogenic tree POLYTOMY:
-When multiple 3+ branches
A branch with more than two lineages is a polytomy.
Monophyletic/Clade:
Includes the most recent common ancestor of the group and all of its descendants (clade)
Paraphyletic:
Includes the most recent common ancestor of the group, but not all of the ancestor’s descendants. Usually only ones that share a certain trait
Polyphyletic (Extant aquatic
plants):
Does not include the most
recent common ancestor of all
members of the group.
some
Clade:
All the organisms within a clade stem from a single point on the tree. A clade may contain
multiple groups, as in the case of animals, fungi and plants, or a single group, as in the case
of flagellates
Scientific names:
Binomial names written in italics, genus/species, with the genus name capitalized
“Tree of life model”
Inspired by a sketch from Charles Darwin. the “tree of life” has a single trunk and many branches.
What was the first virus to be discovered?
The tobacco mosaic virus
Fundamental properties of life:
-Growth
-Cellular division
-Sensitivity
-Development
-Reproduction
-Regulation
-Homeostasis
-Heredity
Structure of all viruses:
-Nucleic acid core surrounded by capsid
-No cytoplasm, not a cell
Nucleic acid can be:
-DNA or RNA
-Circular or linear
-RNA may be segmented or not
-Single/Double stranded
How are viruses classified?
-By genome
-RNA viruses, DNA viruses, retroviruses
T or F: Viruses are very diverse
T
-Structure, host species, and replication change wildly
Virions:
-are infectious virus particles outside cells
-Viruses are not alive or dead but inactive or active
Capsid:
a protein sheath that most viruses develop around their nucleic core.
(composed of repeats of ~1-3 proteins)
Many animal viruses have:
an envelope derived from host cell membranes w/ vital proteins
The 2 most common virus shapes:
– Helical (filamentous) – rodlike or threadlike
– Icosahedral – 20-sided (similar to soccer ball)
Complex viruses:
– T-even bacteriophage – binal symmetry
(head-to-tail)
– Poxviruses – multilayered capsid
Glycoproteins:
can attach to host cell surface receptors to facilitate infection
T or F: Viruses can reproduce anywhere
F. Viruses can only reproduce inside cells, outside they are metabolically inert virions.
T or F. Virions have plenty of ribosomes and enzymes for protein synthesis
F. They lack ribosomes/enzymes required for protein or nucleic synthesis
Viral Genomes:
Vary greatly in both the type of nucleic acid and # of strands
Most RNA viruses are:
-Single stranded
-Replicated in host cell’s cytoplasm
-Replication in cytosol is error-prone (high rates of mutation/difficult targets for immune system)
Baltimore classification system:
Substantial variation exists in how mRNA is produced.
Positive strand virus:
viral RNA serves as mRNA (Group IV: Coronaviruses)
Negative-strand virus:
genome is complementary to the final mRNA (Group V: influenza, rabies, ebola)
Retroviruses:
employ reverse transcriptase to reverse transcribe viral RNA into DNA (Group VI: HIV)
Most DNA viruses are:
-Double stranded
-replicated in the nucleus of eukaryotic cell
Viruses are found:
in every kind of organisms investigated, more viruses exist than organisms.
Host range:
types of organisms infected, each virus has a limited host range.
Tissue tropism:
inside a host the virus may only
infect certain tissues (e.g., rabies – nervous tissues)
Permissive cells:
Allow viral entry
T or F Viruses can remain dormant/latent for years.
T. Chicken pox can reemerge as shingles.
Virus reproduction cycle:
- Attachment/adsorption
-Penetration/injection/entry
-Synthesis/replication
-Assembly
-Release/egress
-Eclipse period
Attachment/adsorption
The target is part of surface of host cell
Penetration/injection/entry
Pierces or fuses with cell membrane to inject
viral genome
Synthesis/replication
-Virus may immediately take over the cell’s
replication and protein synthesis enzymes to
synthesize viral components
Assembly:
-Assembly of viral components to produce virions
Release/egress
-– Mature virions are released via enzymatically lysing host or budding through host cell membrane
Eclipse period:
- Time between attachment and the formation of new viral particles
– If a cell is lysed during eclipse period, few if any active virions can be released
Bacteriophage:
-Viruses that infect bacteria
-Diverse; united only by bacterial hosts
-Called phage for short
Lytic cycle (virulent virus):
-Virus lyses the infected host cell
Lysogenic cycle (temperate virus):
-Virus doesn’t immediately kill the infected cell
-Virus nucleic acid is integrated into hose cell genome prophage
-Integration allows viral DNA to be replicated along
with the host cell’s DNA as the host divides
Phage conversion:
– Phenotype or characteristics of
the infected (lysogenic) bacteria -
altered by the prophage
– Prophage genes are expressed
Phage conversion of
Vibrio cholerae (type of bacteria):
-phage contains gene for cholera
-Gene is incorporated into bacterial
host genome
-Cholera toxin expression converts
harmless bacteria into disease-
causing cholera
Plant viruses:
-Galls, chlorosis
(yellowing), necrosis
(dead tissue),
abnormal growth
-Can result in
substantial economic
losses (crops and
landscaping plants)
Vaccinations:
-Gives immune system information
– “Live” attenuated virus – causes infection but
symptoms are generally very mild (e.g., smallpox)
– “Killed” vaccine uses viral glycoproteins or other viral
molecules (unable to infect)
– mRNA vaccine provides information about surface
proteins (e.g., spike protein)
– Not associated with autism
– Limits community spread and severity
– Limits mutations -> variants (some are dangerous)
Antiviral drugs:
-Help limit symptoms
-Generally limited success in curing
Human immunodeficiency virus:
- HIV/AIDS causes acquired immune deficiency syndrome
-Frist reported in the US 1981
-African origin 1950’s
Those found resistant to HIV:
– Exposed repeatedly never become positive
– Others become HIV-positive without developing AIDS
– Others have little resistance and progress rapidly
from infection to death
– Resistance may be related to smallpox resistance (lack surface receptor)
HIV targets:
CD4+ cells, mainly helper T-cells
Helper/T-cells
– Without these cells, the body cannot mount an effective immune response
– Host may ultimately die from opportunistic infections (otherwise rare conditions)
– Clinical symptoms usually appear after 8–10 year latent period
HIV infection cycle:
- Attachment
- Entry
- RNA -> DNA
- DNA -> host genome
- Transcription -> viral genome and viral proteins
6/7. HIV assembly and export
Influenza:
-One of the most lethal viruses in human history
– 20–50 million people died worldwide between 1918 and 1919.
Flu viruses are enveloped in _____ viruses
Animal
3 types based on capsid protein
-Type A serious epidemics in humans and other animals
-Type B/C mild human infections
Subtypes:
– Hemagglutinin (H) – Aids in viral entry
– Neuraminidase (N) – Aids in viral exit
Flu viruses can also undergo:
-Genetic recombination when 2 subtypes infect the same cell
-creates novel combinations of spikes unrecognizable by human antibodies
Antigenic shifts have caused the following pandemics:
– Spanish flu of 1918, A(H1N1)
* Killed 20–50 million worldwide
– Asian flu of 1957, A(H2N2)
* Killed over 100,000 Americans
– Hong Kong flu of 1968, A(H3N2)
* Infected 50 million in U.S.
* Killed 70,000 in U.S.
Emerging viruses:
-Are viruses that extend their host range
-Often deadly to new host
Hantavirus:
-Causes deadly pneumonia
-Natural host is deer mice
-Controlling deer mice has limited disease
Ebola virus:
– Causes severe hemorrhagic fever
– Among most lethal infectious
diseases (70-90% mortality)
– Host – great apes and bats
SARS-CoV-2:
– Severe acute respiratory syndrome
– Also affects other systems
– Drug treatments are being developed and tested
– Long-term efficacy of vaccines is being evaluated
Virus & Cancer relationship:
-Viruses may contribute ~15% of all human cancers
-They cause cancer by altering the growth properties of human cells
Prions
“Proteinaceous infections particles”
-Causes transmissible spongiform encephalopathies. (Mad cow)
-Host has normal prion proteins, misfolded ones cause disease
Viroids:
-Tiny naked molecules of circular RNA (no protein)
-Causes diseases in plants
