Download D5 Phylogeny and systematics – summary of mark

D5 Phylogeny and systematics – summary of mark schemes
D.5.2
Explain the biochemical evidence provided by the universality of DNA and protein structures for the common ancestry of living
organisms.
Mark Schemes
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B.
C.
D.
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G.
H.
I.
J.
D.5.4
chemical homology of molecules / closeness of structures;
indicate common ancestry;
phylogeny / evolutionary history of a species / relationship between species can be determined;
proteins analysed for amino acid sequences;
more similar the amino acid sequence, the more closely related the species are;
eg cytochrome C / hemoglobin / chlorophyll / other valid example;
DNA / mitochondrial DNA / gene nucleic acid sequence analysed;
differences due to mutations at a certain rate / the number of differences is proportional to the length of time since
two species diverged;
evolutionary / molecular clock indicates closeness of species;
DNA – DNA hydridization;
Discuss how biochemical variations can be used as an evolutionary clock.
Mark Schemes
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B.
C.
D.
E.
mutations cause changes in the protein structure;
mutations have a fixed frequency of occurrence;
protein structure from common ancestor changes over time;
the greater the difference between proteins, the more mutations have occurred;
species more closely related have less differences in their protein structure;