Cladistics Cladograms Assignment

Cladistics Cladograms Define clade and cladogram A clade consists of a single common ancestor and all of the descendants of that ancestor Clade: ……………………………………………………………………………………………………………………………………………... Tree diagrams where branch points show splitting of two new groups from a common ancestor Cladogram: ……………………………………………………………………………………………………………………………………... Explain how biochemical evidence can be used to demonstrate evolutionary relationships The genetic code is (almost) universal and hence DNA and proteins can be compared to determine relatedness ………………………………………………………………………………………………………………………………………………….......... Mutations naturally accumulate and so sequence differences demonstrate the degree of divergence ………………………………………………………………………………………………………………………………………………….......... (the more similar the base sequences, the more closely related the two species are expected to be) ………………………………………………………………………………………………………………………………………………….......... Non-coding DNA mutates the fastest, followed by gene sequences, with amino acid sequences mutating slowest ………………………………………………………………………………………………………………………………………………….......... With the aid of the diagram, explain the advantages of mitochondrial DNA as a phylogenetic tool mtDNA is commonly used for comparing species that are closely related ………………………………………………………………………………………………………………… It is inherited maternally (more direct lineage) ………………………………………………………………………………………………………………… It lacks recombination (as mtDNA is circular) ………………………………………………………………………………………………………………… Has a relatively stable (and high) mutation rate ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… Explain the concept of the ‘molecular clock’ as a means of dating evolutionary relationships Some genes or protein sequences may accumulate mutations at a constant rate (i.e. molecular clocks) ………………………………………………………………………………………………………………………………………………….......... The time of divergence can be calculated based on the total number of mutations ………………………………………………………………………………………………………………………………………………….......... Different genes may change at different rates and rate of change may differ between species ………………………………………………………………………………………………………………………………………………….......... Over long periods, earlier changes may be reversed by later changes, (confounding accuracy of predictions) ………………………………………………………………………………………………………………………………………………….......... Give two examples of when molecular evidence was used to reclassify existing schemes Species in the Figwort family have been reclassified based on chloroplast DNA 1. …………………………………………………………………………………………………………………………………………………... The Homininae sub-family was created to group gorillas and humans together 2. …………………………………………………………………………………………………………………………………………………... Compare homologous and analogous structures Homologous Structures Analogous Structures Look different Look similar Due to different selection pressures Due to common selection pressures Organisms share a common ancestry Organisms do not share a common ancestry Arise via divergent evolution Arise via convergent evolution Example: Pentadactyl limb in vertebrates Example: Fins in dolphins and sharks …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. …………………………………………………………………………. Construct a simple cladogram from the following information Taxa Characteristics Bat Fur, jaws, lungs, mammary glands Eagle Jaws, lungs Kangaroo Fur, jaws, lungs Shark Jaws Chimpanzee Fur, jaws, lungs, mammary glands, opposable thumbs Shark Jaw Eagle Lungs Kangaroo Fur Bat Mammary glands Opposable thumbs Chimpanzee