Exam 2 Flashcards
Bacteria
No nucleus
Archaea
Cells do not contain a nucleus; they have a different cell wall from bacteria
Eukarya
cells do contain a nucleus.
Branch Point
indicates where two lines diverges
Basal Taxon
A lineage that evolved early and remains unbranched
sister taxa
when two lineages stem fro the same branch point
Clade
a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor (also monophyletic group)
Monophyletic
consists of an ancestral species and all of its descendants
Paraphyletic
consists of an ancestral species and some, but not all, of its descendants
Polyphyletic group
includes distantly related species but does not include their most recent common ancestor
limitations of phylogenetics trees
-closely related taxa may look similar, but not always.
-if evolved under different circumstances (selection pressure) taxa may look every different
Taxonomy
grouping of classifying species together based on similarities & differences.
Taxa
hierarchy of groupings
Linnaean classification system
Domain, Kingdom, phylum, class, order, family, genus, species
Dear king philip came over for good soup
Advantages of phylogenetic classification
-tells evolutionary history
- does not “rank” organisms and does not suggest that 2 identically ranked groups are comparable.
Cladistics
method of hypothesizing relationships among organisms; divergence of taxa as a result of evolution
Characters
anatomical or physiological or behavioral or genetic sequences
Shared Ancestoral character
Characteristic found in the ancestor of a group.
Shared derived character
Characteristic only found in some of the organisms in a group. This is because this characteristic derived at some point, but does not include all of the ancestors in the tree.
Maximum parsimony
least amount of DNA base changes.
Principle of maximum parsimony
-fewest evolutionary events
-events occurred in the simplest, most obvious way
Horizontal Gene transfer
Transfer of genetic material from one species to another species.
More prevalent in prokaryotes
Mutations and HGT are important sources of genetic variation
Three primary models of HGT
Transformation
Transduction
Conjugation
Transformation
naked DNA uptaken by bacteria
transduction
Genes transferred from one cell to another by a bacteriophage
Conjugation
genes transferred between two bacterial via the pilus (direct contact)
Transposons
Jumping genes; mobile section of DNA that can move between genomes
endosymbiont
When a cell lives inside another cell with mutual benefit.
Endosymbiotic Theory
Eukaryotic cells are believed to have evolved from early prokaryotes that were swallowed.
ex: mitochondria and chloroplasts are both organelles suggested to have arisen via endosymbiosis.
Classic Tree model
Originated with Charles Darwin; does not account for HGT
Web and Network Models
Eukaryotes evolved not from a single prokaryotic ancestor but from a pool of many species sharing genes by HGT.
Ring of Life Model
Proposed that all three domains evolved from a pool of prokaryotes swapping genes via HGT.
Discover of Viruses
Electron microscope allowed the first views of viruses.
First seen / discovered virus
Tabacco mosaic Virus (TMV)
Three hypotheses aroun the evolution of Viruses
Regressive, Progressive or Escapist, Self replicating
Regressive Hypothesis
Viruses evolved from free-living cells or from intracellular prokaryotic parasites
Progressive or Escapist Hypothesis
Viruses originated from pieces of DNA that escaped from a host cell and gained the ability to to move between cells
Self-replicating hypothesis
Viruses may have originated from self-replicating entities similar to trasposons (jumping genes) or other mobile genetic elements
Viral morphology
- single virus particle, sized around 20-250 nm (super small)
- noncellular; lacks almost all cell components
- made up of nucleic acid core, capsid and SOMETIMES outer envelope.
Virus shapes
Helical, icosahedral, enveloped, complex
Helical
long and cyndrical
-> ex: TMV
Icosahedral
roughly spherical shaped (non enveloped)
-> ex: Adenovirus
Enveloped
have membranes surrounding the capsids
-> ex: Influenza virus
Complex/Head and tail
infect bateria and gave a head that is similar to icosahedral viruses and a tail shaped like helical viruses
-> ex: Bacteriophage
Genome
total genetic content of a virus; only codes for proteins that the virus can get w/o the host
Viruses that encode their own enzymes use?
RNA Dependant RNA Polymerase (RDRP)
Why are there more errors in the enzymes RNA viruses use?
RNA doesn’t have a self checker like DNA does, so mistakes go unchecked.
DNA Viruses
- Often double stranded but can be single stranded.
- Replication in nucleus
- Some may have DNA polymerase and so they’ll do replication in the host cell’s cytoplasam
-> ex: small pox virus
RNA Viruses
- Usually single stranded but can be double stranded
- Replication happens in cytoplasam
- Mutations happen very often bc RNA polymerase does not have a proofreader
-> Ex: Influenza viruses, coronaviruses.
Baltimore classification system
Groups viruses based on how the mRNA is produced during the replication cycle of the virus.