● Naming species: it can be difficult
○ Issues with language, personal biases, and different naming conventions affect the naming process
○ So there needs to be a universal naming system for naming organisms ○ Carolus Linnaeus:proposed that Latin should be the common language for naming (wrote Systema Naturae)
■ Said each organism gets two names “binomial nomenclature” ● Genus, species (ex. Homo Sapiens)
■ Came up with the system of hierarchical nomenclature
● Kingdom, Phylum, Class, Order, Family, Genus, Species
■ (1977) Carl Woese: added Domain to the system of hierarchical
● Domain: Bacteria, Archaea, Eukarya
■ Because this system had difficulties with displaying evolutionary
relationships, it led to Phylogenetics
● Phylogenetics: a field that uses techniques and tools for reconstructing evolutionary relationships based upon evidence of common ancestry
○ Common ancestry is observed by fossils sharing the same characteristics (ex. hair on mammals)
■ Also by using genetic comparisons
○ Phylogenetics is a tool used in systematics Don't forget about the age old question of What happens when you cut off blood supply?
● Systematics: method or approach for classifying and naming organisms in an evolutionary framework
● Cladograms(phylogenetic trees): shows relationships between organisms ○ The base of the tree is the common ancestor, with branches that show different characteristics (everything below it lacks that characteristic, everything above it possesses that characteristic)
■ ex. Lamprey, Shark, Salamander, Lizard, Tiger, Gorilla, Human
■ ex. Carl Woese’s Domains: common ancestor (base), Bacteria, Archaea, Eukarya
● Bacteria and Archaea: prokaryotes (on the branch)
● Eukarya: membranebound nucleus (on the branch)
● Carl Woese found that bacteria and archaea differ in how they synthesize/make proteins ● Ch. 27
● Virsuses:infect every group of organisms on the planet If you want to learn more check out Why did the sampoong department store collapse?
○ Morphology is used to classify viruses based on two characteristics ■ Some sort of genetic material (RNA vs. DNA)
■ The type of capsid:outer protein covering that encases the genetic material (all viruses have a capsid)
○ Also classified based upon genetic material (some where main genetic material is RNA, some where main genetic material is DNA)
■ RNA viruses are much more likely to mutate and change form
■ The genetic material carries instructions on how to hijack cells and how to produce new viruses
● Virus structure:
○ Tail: used for leverage to penetrate the cell wall
● Bacteriophages: viruses that only infect bacteria
○ Very complex “virions”
○ Virion: individual virus
○ Tail fibers and whiskers: affect host recognition (if they don’t recognize the cell type they won’t fasten on to it)
○ Lytic Cycle: phases bacteriophages go through to replicate
■ Attachment: where they penetrate the cell wall of the bacteria
● Then injects it’s genetic material into the cell
■ Synthesis stage: once it’s inside the cell, the viral DNA takes over the cellular replication and protein synthesis machinery to make parts of a new virus
■ Assembly stage: all viral pieces come together, forming virions We also discuss several other topics like How do we learn gender roles?
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■ Release: where individual virions rupture and break through the cell, and enter the environment to infect other bacteria
○ Lysogenic cycle: the host cell does not die (different from Lytic Cycle) inactive phase for the virus
■ Integration: the viral DNA becomes part of the bacterial DNA (leads to prophage)
■ Propagation: where it replicates with the host cell genome when the cell divides (can continue through many cycles until something breaks the cycle)
■ Cell stress: food availability, environmental change, toxins (antibiotic) ■ Induction: viral DNA exits the genome
● Then goes on to the Lytic Cycle