Phylogenetics
Genomic sequencing can be used to work out the evolutionary relationships of different species, or groups of organisms. This is known as phylogenetics.
Species with more similarity in their genomes are more closely related. Phylogenetics can be used to work out:
- lineage - the exact sequence in which species can be traced back through ancestor populations
- sequence divergence - how and when lineages diverged from common ancestry
The diagram below shows a phylogenetic tree. Comparison of sequences has provided evidence for this division of living things into three key lineages – bacteria, arcaea and eukaryotes.
The use of sequence data has improved our understanding of the evolution of life on Earth. For example, along with evidence from fossils, phylogenetics has been used to determine the following sequence of events:
- cells
- last universal ancestor (the most recent population of organisms from which all others are descended)
- photosynthetic organisms
- eukaryotes
- multicellular life
- animals
- vertebrates
- land plants
Molecular clocks
Molecular clocks measure the number of mutations that accumulate in a DNA sequence over time using sequence data and we can use this information to work out when speciation occurred and when one lineage separated into two new lines.
Molecular clocks assume a constant mutation rate and show differences in DNA sequences or amino acid sequences. These differences in sequence data between species indicate the time of divergence from a common ancestor.