Classification and Cladistics

taxonomy

scinece of classifying oragnisms into groups.

Groups are called taxa

• based on observeable physical traits

once you know the characteristics of known mammals

you know the characteristics of all mammals, even the undiscovered ones

how many species on earth

8.7 million

Taxomy

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Dashing king Philip came over for great soup

Based on cladistsic what does not exist

reptiles

Traditional classification grouped reptiles into a single taxon (Class Reptilia), but this does not correspond to patterns of divergence by evolution.

Cladistics groups organisms into clades, where all members of a clade share a common ancestor. Birds are more closely related to crocodiles and turtles than other reptiles, therefore birds, crocodiles and turtles are classified into a single clade.

paradigm shift

fundamental change in understanding

Taxomy→ cladistics

evolution

change in heretiable characteristics of populations of a species over time

The ideal classification  system follows evolutionary relationships, so all the members of a taxonomic group have evolved from

a common ancestor

cladistics

methods of classifying organisms into clades based on shared characteristics

clade

group of organisms or viruses that have all evolved from a common ancestor. Characteristics can be preditced according to cladss classified in

Morphological traits can be used

cladogarms

tree diagramd that organize clades, show probable divergence of species

classifying clades

• objective

  • base sequence, amino acids

  • DNA, RNA, protein sequences

• organisms evolve and diverge, their DNA sequences accumulate mutations. Scientists compare these mutations using sequence alignments to reconstruct evolutionary history

molecular clock

diffrences in base sequence of DNa are the results of proteins

Mutation gradually accumulate over long periods of time at a constant rate so they can be used as a generational clock to see when species diverged from a common ancestor

limits to a molecular clock

generational time- shorter generation time, more opportunity for mutaitons, faster clock

population size- mutaitons are more likely in fixed, small populations resulting in faster molecular clocks

selective pressure-

node

divergince of species from a common ancestor

cladograms are created by grouping oragnisms bu

shared charactersitics

• BAse sequence of genes/amino acids

• nucleotides sequence

fewer differences, more closly related species are

parsimony analysis

used to select the most probable cladogram, in which observed sequence variation between clades is accounted for with the smallest number of sequence changes.

• assumption of parsimony analysis is that a simple hypothesis with a small number of evolutionary changes is more likely to be true than a complex hypothesis.

rapidly evolving cirus

• Rapidly evolving viruses can quickly develop resistance to existing drugs and treatment, requiring more research and development of new drugs.

• The mutations often produce novel subtypes of the virus, which are no longer recognised by the immune system.

• impact the effectiveness of current vaccines, which may no longer confer immunity.

not contained, it can result in epidemics or pandemics.

terminal brance

endpoint representing one group

root

represents theoretical last common ancestor, LUCA

Figwort faimily reclass

• orignlally made using morphology, reclassified by cladistics

  • compared nucleotides sequence of 3 chloroplast genes

• Fifty genera were reclassified into the plantain family (Plantaginaceae).

• Twelve genera were reclassified into the broomrape family (Orobanchaceae).

• Thirteen genera were classified into a new family, lindernia (Linderniaceae)

• Two genera were were reclassified into a new family, calceolaria (Calceolariaceae).

• Two small families of other plants were reclassified into the figwort family.

Three Domains

Bacteria

Archaea

Eukaryotes

A and E are more closely related

eurobacteria vs archaea vs eukarya