taxonomy and phylogenetics

what is the importance of taxonomy to biology , health, and industry?

understanding agricultural pests-so can be controlled

understand different variants and origins-e.g. of COVID19- drove welsh border policy

what is taxonomy

theory and practice of classification, establishes identify and describes organisms

what is systematics?

process to classify organisms according to their phylogeny

what are phylogenetics?

study of the ‘tree of life’- evolutionary history of taxonomic groups

who were the first classifiers?

indigenous peoples-aborigines, native Americans, Inuit

useful to survival- edible vs poisonous, harmless vs dangerous

who was one of the earliest classifiers?

Aristotle (e.g. land vs water vs air dwellers) 384-322BC

how many species are there? how many have we catalogued?

10.9 million, 1.4 million (majority prolly insects)

what does classification involve?

arranging populations & species into groups

groups based on shared characteristics- ordering & ranking them

what did Linnaeus do?

developed taxonomic hierarchy of categories (not domains)

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what are some of the new theories in science 1700-1800 that led to darwins theories?

-fossilisation

-age of earth

-extinction

-evolutionary forces -Lamarck said giraffe necks grow as they stretch them

-homology

-vestigial structures

darwins finches- ultimately caused him to think about beak morphology and their relationships

what is the theory of common descent?

all life on earth shares a common ancestor

explains y members of taxonomic group more similar to one another than others

who had some similar theories to the theory off common descent?

Alfred Russel Wallace- Sarawak law

John Hunter- arrived at the idea before both but too radical

what is the typological species concept?

typology based on morphology/phenotype

what are some issues w the typological species concept?

ignores intraspecific variation- different sexes sometimes look v different, or have different life stages (e.g. caterpillar), sometimes different geographic variants still same species (e.g. African, Asian, European skin colour)

what is the biological species concept?

based on mendelian & post-mendelian genetics

species=can breed together- reproductive isolating mechanisms

what are the cons of biological species concept?

excludes asexually reproducing organisms & fossils

sometimes there are intermediates becoming species

allopatric species (geometric separation) are tough

some species never observed mating e.g. ring species (diff location but are same species)

what are some cons and pros of morphospecies?

pro- morphology largely under genetic control, usually later found to be biological species

con- cryptic species (same morphology, diff behaviour & genes)

what is a subspecies?

aggregate local pop of an individual species CANNOT B SYMPATRIC

what is a polytypic species, how do they arise?

several subspecies, (a trinomen is used), due to reduced gene flow, subspecies eventually become separate species

what are some other species concepts?

recognition species concept- if recognise each other as mates

phylogenetic species concept- species is smallest inclusive monophyletic grouping

genetic species concept-genetic similarity

pros and cons of recognition species concept?

pros- removes uncertainty in allopatric pops , relies entirely on mechanism

cons- excludes asexuals, intermediates excluded, only rlly works with animals, harder to asses than biospecies

pros and cons of phylogenetic species concept?

pro- recognises role of history, can use any data

cons- subdivisions can be arbitrary, subspecies not recognised & ring species not differentiated

pros and cons of genetic species concept?

pro-independent evidence, can deal w asexuals, can find cryptic species

cons- still subjective,

what can classification be used for?

enables predictions & generalisation

what is the process of classification?

delimitation, ordering, ordering, ordering

what is topology?

arrangement of tree branches and stems

what is ranking?

conferring status on supraspecific groups

difference between a dendrogram and phylogenetic tree?

a dendrogram is a phylogenetic tree, no indication of how similar each group is

what are the principles of phenetics?

-based on phenotypic similarity

-all characters given equal rating

-genealogy & evolutionary history ignored

what is a massive problem with phenetics?

convergent evolution & mimicry

what are the principles of cladistics?

-based on inferred genealogy

-trees r cladograms

-weighting of characters

-based on shared, derived homologous characters

-paraphyletic &polyphyletic taxa are invalid

what are the 3 reasons taxa resemble one another?

-character arose before nearest common ancestor

-character came from nearest common ancestor-shared derived

-character originated independently, via convergence (homoplasy)

when a characteristic has polarity (2 states- e.g. egg inside or outside) how is it determined which trait is older?

-outgroup comparison

-embryology

-fossil record

what are the cons of cladistics?

-ignores anagenesis (opposite to cladogenesis) (non branching lines of descent)

-sister taxa given same rank (but birds vs crocodiles-birds are much more different to common ancestor)

what is orthodox classification?

-based on cladogenesis & anagenesis

-weighting homologous characters

-trees r phylograms