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Principles of classification
Classification: grouping together similar organisms.
Taxonomy (science of classification) makes it easier to identify and study organisms.
Seven levels: Kingdom, Phylum, Class, Order, Family, Genus, Species (group of similar
organisms that can produce fertile offspring).
Phylogenetics: an organism's evolutionary history.
Tells us how closely related species are.
Distinguishing species: e.g. fertile offspring.
Reasons why reproductive behaviour difficult to determine: extinct, asexual reproduction,
practical reasons (geographical), ethical reasons (lab study).
DNA is used to classify.
Species classification: DNA or proteins
Taxonomic hierarchy based on similarities and diff in their genes
Done by comparison of DNA sequences
Hybridisation: DNA sequencing and hybridisation
Sequencing: order of bases, (G,C, A, T) closely related will have higher percentage in
similarity of base order.
Hybridisation: single strands of 2 different species' DNA mixed together, same base
sequences (specific base pairing) cause hydrogen bonds to form. Heating used to separate
(hotter the temp needed the more hydrogen bonds form therefore more similar DNA)
Proteins: similar organisms will have similar proteins.
Amino acid sequence sequence coded for by base sequence. Similar organisms will have
similar DNA base sequence
Immunology comparisons similar proteins will bind the same antibodies.
Interpreting data: On DNA and protein similarities
If data % - higher percentage = more similarities
Amino acid sequences similar sequences = similar organisms.
Courtship behaviour: each species has specific behaviour
Used to attract mate of the same species. E.g. use of chemical or displays
Species specific each species have own call and response pattern so mating will only ensure
if both partners same species.
The more closely related a species the more similar their courtship behaviour.