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Its genetic material was most likely DNA, [15] so that it lived after the RNA world. [a] [18] The DNA was kept double-stranded by an enzyme, DNA polymerase, which recognises the structure and directionality of DNA. [19] The integrity of the DNA was maintained by a group of repair enzymes including DNA topoisomerase. [20]
Molecular evolution describes how inherited DNA and/or RNA change over evolutionary time, and the consequences of this for proteins and other components of cells and organisms. Molecular evolution is the basis of phylogenetic approaches to describing the tree of life. Molecular evolution overlaps with population genetics, especially on shorter ...
However, fossil evidence is scant, and only with the evolution of the diatoms themselves do the heterokonts make a serious impression on the fossil record. The earliest known fossil diatoms date from the early Jurassic (~185 Ma ago ), [ 59 ] although the molecular clock [ 59 ] and sedimentary [ 60 ] evidence suggests an earlier origin.
The history of the camel provides an example of how fossil evidence can be used to reconstruct migration and subsequent evolution. The fossil record indicates that the evolution of camelids started in North America (see figure 4e), from which, six million years ago, they migrated across the Bering Strait into Asia and then to Africa, and 3.5 ...
A very large number of fossils have now been discovered and identified. These fossils serve as a chronological record of evolution. The fossil record provides examples of transitional species that demonstrate ancestral links between past and present life forms. [45]
Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived. First pelicans. 25 Ma Pelagornis sandersi appears in the fossil record, the largest flying bird that ever lived. 25 Ma First deer. 24 Ma First pinnipeds. 23 Ma Earliest ostriches, trees representative of most major groups of oaks have appeared by now ...
Mitochondrial DNA (also known as mtDNA) was sequenced from desiccated muscle of the quagga, and was found to differ by 12 base substitutions from the mitochondrial DNA of a mountain zebra. It was concluded that these two species had a common ancestor 3-4 million years ago, which is consistent with known fossil evidence of the species. [28]
The best time to extract DNA from a fossil is when it is freshly out of the ground as it contains six times the DNA when compared to stored bones. The temperature of extraction site also affects the amount of obtainable DNA, evident by a decrease in success rate for DNA amplification if the fossil is found in warmer regions.