Final answer:
Phylogeny is the study of the evolutionary history and relationships among organisms, represented by phylogenetic trees constructed by systematics using data from multiple sources including DNA analysis.
Step-by-step explanation:
Phylogeny is defined as the evolutionary history and relationship of an organism or group of organisms. The field of science that uses such information to classify and organize organisms based on their evolutionary relationships is called systematics. Phylogenetic trees are diagrams that represent these relationships, showing how species are related through common ancestors. The nodes on these trees mark points where, according to scientific evidence, an ancestor diverged to form new species. However, these trees are hypotheses and may change with new discoveries and information.
Data used in constructing phylogenetic trees can come from various sources such as fossils, body structures, molecular analysis, and especially DNA sequences. As a result, phylogenetic trees help scientists understand the evolution of life, although they may not always show organisms that look alike, as closely related species can evolve differently under different environmental conditions.